TOPIC No.1: Congenital anomalies that cause intestinal obstruction in children.
Plan:
1. Congenital anomalies that cause high intestinal obstruction in children.
1.1. Pyloric stenosis.
1.2. Congenital duodenal obstruction.
1.3. Volvulus neonatorum-Ladd’s syndrome.
2. Congenital anomalies that cause SMALL BOWEL obstruction in children
2.1. Atresia and stenosis of the small intestine.
2.2. Meconium ileus.
3. Congenital anomalies that cause LARGE BOWEL obstruction in children
3.1. Atresia and stenosis of the large intestine.
3.2. Hirschsprung’s disease.
3.3. Anorectal malformation.
1. Congenital anomalies that cause high intestinal obstruction in children
1.1. Infantile hypertrophic pyloric stenosis
Pathophysiology. Diffuse hypertrophy and hyperplasia of the smooth muscle of the antrum of the stomach and pylorus proper narrow the channel, which then can become easily obstructed. The antral region is elongated and thickened to as much as twice its normal size. In response to outflow obstruction and vigorous peristalsis, stomach musculature becomes uniformly hypertrophied and dilated. Gastritis may occur after prolonged stasis. Hematemesis is occasionally noted. The patient may become dehydrated as a result of vomiting and develop marked hypochloremic alkalosis.
Frequency. Pyloric stenosis is a common cause of gastric outlet obstruction in infants. The prevalence of HPS ranges from 1.5-4/1000 live births among whites, although it is less prevalent among African and Asian Americans.
Clinical features. The peak incidence for the onset of symptoms is between the 3rd and 6th weeks of life. However, the condition can commence before that time, and as late as the 7th week. The pillars upon with the diagnosis rests are:
Vomiting is the presenting symptom in all cases and withing 2 or 3 days it becomes forcible and progectove. Bile is not present in the vomiting. Immediately after vomiting the baby is often very hungry.
Visible peristalsis. After the child has been fed, peristaltic waves may be seen passing from the left to right across the upper abdomen. It is the so-cold symptom of “sand clock”. A ggod light is essential for this. The abdomen should be examined throughout a feed until vomiting occurs.
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The presence of a lump. The palpation of the hypertrophyed pylorus is the most essential step in reaching a diagnosis. The surgeon should palpate under the liver with a warm hand. It may be helpful to examine the child more than once. The lump is most easily felt when the child is given a feed.
Constipation is usually present, and when a stool is passed it is small and dry. It is important to ask the mother about napkins. If the child is dehydrated, they are not wet and the case is correspondingly more urgent.
One of the most striking signs of infants sufferinf from IHPS is loss of weight. Moreover, it is not long before the infant begins to look emaciated and dehydrated.
Often a change from one type of feeding to another brings about a remission. Consequently a series of changes in diet are sometimes made before the diagnosis is established, by with time the infant`s condition may be pitiable.
In prematures infants, in whom the condition is not uncommon, the symptomatology is often paradoxical. There is anorexia instead of voracious appetite; the vomiting is regurgitant rather than projectily, and so frequently is peristalsis normally visible. None the less, amids this sea of bewilderment one diagnostic rock remains – a hypertrophied pylorus can be felt through the poorly-developed abdominal wall with comparative ease.
Imaging Studies
Ultrasonography has become the criterion standard imaging technique for diagnosing HPS. It is reliable and easily performed. An experienced ultrasonographer increases the test’s predictive value. Necessary measurements include pyloric muscle thickness and pyloric channel length. Muscle wall thickness
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Normal pylorus. (A), (B) and (C) Transverse sonograms at the level of the pylorus. The patient has been given clear fluid in order to delineate the antrum and to observe fluid movement through the pylorus. The normal pylorus actively peristalses and fluid passes into the duodenum with ease. This is a good view to obtain when looking for pyloric stenosis. |
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Sonographic measurements of pyloric stenosis |
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Muscle thickness > Canal length > Pyloric diameter > Pyloric volume > 12 ml |
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Pyloric stenosis. (A) Transverse sonogram of the pylorus in an infant with projectile vomiting and suspected of having pyloric stenosis. There is thickening of the pyloric muscle around the echogenic mucosa centrally. The gallbladder is draped over the top. (B) Longitudinal sonogram of the pyloric canal. There is marked thickening of the pyloric muscle (between calipers 1) and lengthening of the canal (between calipers 2). (C) Barium has been introduced into the stomach via a nasogastric tube. There was very active antral peristalsis and an elongated and narrowed pyloric canal. There is the typical double channel of pyloric stenosis with delay in gastric emptying because of the gastric outflow obstruction. |
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Barium upper gastrointestinal (UGI) study is an effective means of diagnosing HPS. It should demonstrate an elongated pylorus with antral indentation from the hypertrophied muscle. The classic “railroad track” sign of two thin parallel streams of barium traversing the pylorus is pathognomonic. Confirming the diagnosis of HPS is impossible if barium does not leave the stomach. Sufficient patience, however, usually demonstrates the above findings. An advantage of a barium UGI contrast study is the ability to identify gastroesophageal reflux, a frequent differential diagnosis of HPS. After UGI, irrigating and removing any residual barium from the stomach is advisable to avoid aspiration.
Although UGI endoscopy would demonstrate pyloric obstruction, physicians would find it difficult to differentiate accurately between HPS and pylorospasm. Endoscopic dilatation has rarely been employed as a method of treatment. This treatment is not standard for HPS; endoscopy should be used rarely, if ever.
Treatment
Preoperative resuscitation: If necessary, administer an initial fluid bolus of 10 mL/kg with lactated Ringer solution or 0.45 isotonic sodium chloride solution. Continue intravenous (IV) therapy at an initial rate of 1.25-2 times the normal maintenance rate until adequate fluid status is achieved.
Adequate amounts of both chloride and potassium are necessary to correct metabolic acidosis. Unless renal insufficiency is a concern, initially add 2-4 mEq of KCL per 100 mL of IV fluid. Adequate chloride for resuscitation can usually be provided by 5% dextrose in 0.4% sodium chloride solution. Avoid adding hypertonic chloride or ammonium chloride.
Urine output and serial electrolyte determinations are performed during resuscitation. Correction of serum chloride level to 90 mEq/L or greater usually is adequate to proceed with surgical intervention.
A nasogastric tube must be placed before the induction of anaesthesia if the tube was not placed pre-operatively. And if the barium meal study has been carried out prior to surgery, it may be necessary to remove the residual barium meal by gastric aspiration and irrigation.The patient is placed in the supine position. After the induction of anaesthesia and endotracheal intubation, careful abdominal palpation will usually identify the site of the pyloric tumour. A 2.5-to 3-cm long transverse incision is made lateral to the lateral border of the rectus muscle. The incision is deepened through the subcutaneous tissue and the underlying external oblique, internal oblique and transverse muscles are split. The peritoneum is opened transversely in the line of the incision. When supra-umbilical skin fold incision is employed, a circumumbilical incision is made through about two-thirds of the circumference of the umbilicus. The skin is undermined in a cephalad direction above the umbilical ring and the linea alba is exposed. The linea alba is divided longitudinally in the midline from the umbilical ring to as far cephalad as necessary to allow easy delivery of the pyloric tumour.
The stomach is identified and is grasped proximal to the pylorus with non-crushing clamp and brought through the wound. Then, the greater curvature of the stomach can be held in a moist gauze swab, and with traction inferiorly and laterally, the pylorus can be delivered through the wound. Grasping the duodenum or pyloric tumour directly by forceps often results in serosal laceration, bleeding or perforation, therefore should be avoided.
The pylorus is held with surgeon’s thumb and forefinger to stabilize and assess the extent of hypertrophied muscle. A seromuscular incision is made over the avascular area of pylorus with a scalpel, commencing 1~2 mm proximal to the pre-pyloric vein along the gastric antrum. The incision should go far enough onto the gastric antrum at least 0.5~1.0 cm from the antropyloric junction where the muscle is thin.
The scalpel handle is used to further split the hypertrophied muscle down to the submucosal layer. Then pyloric muscle is spread widely. Spreader is placed at the midpoint of incision line and muscle is spread perpendicularly and spreading must be continued proximally and distally. Gentle spreading is required to obtain a complete myotomy. Mucosal tears are most common at the pyloroduodenal junction because of the attempt to split all remaining muscle fibres. In order to reduce the risk of mucosal tear, care should be taken when spreading pyloric muscle fibres at the duodenal end. Loose prolapsing of intact mucosa is evidence of a satisfactory myotomy. To test the mucosal injury, the stomach is inflated through the nasogastric tube, and passage of air through the pylorus to duodenum is confirmed. Then the pylorus is dropped back into the abdomen. Bleeding from the myotomy edge or submucosal surface is frequently seen; however, it is generally venous and always stops after returning the pylorus to the abdominal cavity. Posterior rectus fascia and peritoneum is approximated with a running 4/0 absorbable suture material and anterior fascia is closed with 5/0 absorbable suture material.
For the laparoscopic procedure the patient is placed in the supine position at the end of the operating table (or 90є to the anaesthesiologist). The video monitor is placed at the head of the table, and the surgeon stands at the end of the table with the assistant to the patient’s right. The abdomen is scrubbed and draped in a sterile fashion.Attention must be paid to ensure the appropriate preparation of the umbilicus. The access sites are injected with local anaesthetic (0.25% bupivacaine) with epinephrine,which is used to reduce the post-operative pain and reduce the risk of bleeding from the stab wound. The author prefers an open procedure for insertion of the primary port. A 4.0- to 5.0-mm curvilinear supra-umbilical incision is made and carried down to the peritoneal cavity. At the level of umbilical fascia, 4/0 absorbable suture material is placed circumferentially to anchor the port and to use for closure of the peritoneal cavity after laparoscopic pyloromyotomy is completed. Intra-abdominal pressure is maintained at 8 mmHg, and insufflation rate is set at 0.5 l/min. In the right mid-clavicular line just below the costal margin (just above the liver edge), a no. 11 scalpel blade is used to make a 2- to 3-mm stab incision under direct vision. Also using the no. 11 scalpel blade, a second stab incision is made under direct vision, just below the costal margin in the left mid-clavicular line. An atraumatic grasper is placed directly through the right upper quadrant stab wound and is used to retract the inferior border of the liver superiorly and expose the hypertrophic pylorus. A retractable myotomy knife (retractable arthrotomy knife or Endotome) is inserted directly through the left stab wound.Working ports are usually not necessary and instruments are directly introduced through these stab wounds.
The working instruments, retractable myotomy knife, atraumatic laparoscopic grasper are used to assess the extent of the hypertrophied pylorus by palpating the margins of the pylorus as one would use with thumb and forefinger in the open procedure. The duodenum is then grasped just distal to the pyloric vein (pyloroduodenal junction) and retracted using the atraumatic grasper to expose the avascular surface of hypertrophic pylorus. The tips of positioning the pylorus for myotomy is that lateral and slightly anterocephalad retraction of the distal pylorus achieve excellent exposure of the avascular surface of hypertrophic pylorus. This manoeuvre also exposes the proximal margin of hypertrophied muscle that is seen as a deep fold in the wall of stomach. A seromuscular incision is made over the hypertrophic pylorus with retractable myotomy knife commencing at 1–2 mm proximal to the pyloroduodenal junction extending to the gastric antrum. The incision should go far enough onto antrum at least 0.5~1.0 cm proximal to antropyloric junction. Care must be taken at this stage that this incision is deep enough to allow the insertion of the pyloric spreader blades and must penetrate the pyloric muscle somewhat deeper than is usual with the conventional open procedure.
After the muscle is incised, the blade is then retracted and the sheath of the knife is used to further split the hypertrophied muscle fibre, as the scalpel handle is used in open procedure, until mucosa is visualized. The retractable myotomy knife is removed and a laparoscopic pyloromyotomy spreader is introduced into abdominal cavity directly through the left stab wound to complete the pyloromyotomy. The spreader is placed in the midpoint of the seromuscular incision line and the muscle is spread perpendicularly. Once the initial spread reaches the mucosa, spreading must be continued proximally and distally. Pushing the spreader towards the mucosa or rapid spreading can result in mucosal tear. In order to avoid the mucosal tear, the spreader should not be placed at the proximal and distal edges of the incisional (myotomy) line. To test for the mucosal injury, the stomach is inflated through the nasogastric tube (160–180 ml) as is usually done in open techniques. Bulging of the mucosal layer with no evidence of defect should be confirmed. Greenish or yellowish fluid at the myotomy area is a sign of mucosal tear. After the successful myotomy, the instruments are withdrawn under direct vision and the pneumoperitoneum is evacuated. The nasogastric tube is also removed after completing the surgery. The umbilical fascia is reapproximated with 4/0 absorbable suture material,which is already in place, and the skin of all the wound is reapproximated with skin adhesive tapes.
Postoperative management
Continue IV maintenance fluid until the infant is able to tolerate enteral feedings. In most instances, feedings can begin within 8 hours following surgery. Graded feedings can usually be initiated every 3 hours, starting with Pedialyte and progressing to full-strength formula.
Complications
Undetected mucosal perforation: Perform a diligent search for mucosal transgressions at the time of operation and examine the infant again before initiating feedings. In those rare cases where a perforation was not detected, the infant develops fever, tenderness in the abdomen, and abdominal distention. Return to the operating theater if perforation is suspected.
Bleeding: In most instances, venous oozing from the myotomy site is self-limited and is not a concern in the postoperative period.
Persistent vomiting: Incomplete pyloromyotomy is rare in the hands of an experienced pediatric surgeon. Less experienced surgeons occasionally commit this error, but they are more likely to cause injury to the mucosa from injudicious spreading during the myotomy. This problem is confounded when repeat studies performed after surgery provide a confusing picture. Patient observation resolves the problem in most cases
2.3. Congenital duodenal ileus
Embryology The hepatobiliary system and pancreas form during the third week of gestation, as the second portion of the duodenum gives rise to biliary and pancreatic buds at the junction of the foregut to the midgut. The duodenum also undergoes a solid phase during this time; between the eighth and tenth weeks of gestation, the duodenal lumen is reestablished by the gathering of vacuoles, and recanalization occurs. Insults during this crucial period of development are believed to result in failure of recanalization and consequent atresias, stenosis, and webs. In addition, duodenal atresias have been associated with a closely surrounding piece of pancreatic tissue. Whether this tissue is an annular pancreas or merely a failure of duodenal development is debatable.
Frequency. Duodenal atresia is present in approximately 1 out of 6,000 newborns.
Mortality/Morbidity. If duodenal atresia or significant stenosis is left untreated, the condition is rapidly fatal owing to electrolyte loss and fluid imbalance.
One half of the neonates with duodenal atresia or stenosis are born prematurely. Polyhydramnios is present in approximately 40% of neonates with duodenal obstruction.
Duodenal atresia or stenosis is most commonly associated with trisomy 21. About 22-30% of patients with duodenal obstruction have trisomy 21. Other problems associated with trisomy 21 include cardiac defects (most commonly ventricular septal defect and endocardial defects) as well as Hirschsprung disease.
Sex: The incidence of duodenal atresia and stenosis is approximately equal in males and females.
Age: Infants with duodenal atresia present with vomiting in their first few hours of life, but patients with duodenal stenosis present at various ages. The clinical findings depend on the degree of stenosis.
Classification. Duodenal obstruction is the result of atresia, stenosis, and duodenal web, annular pancreas, or peritoneal bands secondary to incomplete intestinal rotation. Intrinsic anomalies of the duodenum occur in several forms. There can be atresia with continuity of the bowel wall, atresia with a fibrous cord joining the segments, atresia with complete loss of continuity of the wall and of the blood supply, and all but complete diaphragm with a small fenestration, or a membranous ring within the duodenum which peristalsis from above forces into the development of a “wind sock”. The dilating effect of the wind sock may produce the appearance of obstruction distal to the actual annulus of the wind sock.
In general, duodenal obstructions may be either preampullary or postampullary; however, most are considered periampullary. The degree of obstruction dictates the amount of resulting pathology. The obstruction causes dilation of the proximal duodenum and stomach as well as hypertrophy and distension of the pylorus. A common variation is the windsock anomaly, in which the duodenum is dilated distal to the point of obstruction because of a prolapsing membrane or web. This may be confused with a more distal duodenal obstruction.
Diagnosis
Prenatal ultrasonography may indicate structural and associated abnormalities, such as a dilated stomach and proximal duodenum. Polyhydramnios indicates that the fetus may be having difficulty swallowing the amniotic fluid, and it is suggestive of GI tract obstruction. Common associated anomalies and chromosomal defects may be assessed by screening maternal serum and amniotic fluid.
In the newborn, clear or bilious emesis is evident within hours of birth. Abdominal distension may or may not be present. An output of more than 20 mL of gastric contents is indicative of possible obstruction (normal gastric capacity is 7 – 10 ml). Patients with a stenosis or web may present later with dehydration or failure to thrive.
Plain radiography is helpful and may reveal the classic double bubble, ie, air in the stomach and duodenum, which is associated with complete or near complete duodenal obstruction. Upright and contrast radiography using air or contrast may confirm the diagnosis. Malrotation with volvulus may also result in duodenal obstruction and a consequent double bubble. Duodenal atresia and malrotation may coexist.
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Duodenal atresia. Note the ‘double bubble’ sign and the absence of gas in distal gastrointestinal tract. |
Treatment
Gastric decompression is essential to prevent aspiration, and thermoregulation should be monitored at all times. When fluid resuscitation has been accomplished, the neonate may proceed to surgery.
The baby is placed supine on the table with a small roll under his upper abdomen and on a warming blanket. Endotracheal anaesthesia is used. A nasogastric tube is passed to decompress the stomach.An intravenous infusion is set up. The abdominal skin is prepared by cleaning with prewarmed povidoneiodine. A transverse supra-umbilical abdominal incision is made
After exposing the peritoneal cavity, the surgeon inspects the entire bowel for the presence of other anomalies. There may be an associated annular pancreas or malrotation in one-third of the patients. If the colon is in a normal position, malrotation is probably not a coexisting factor.The stomach and first portion of the duodenum are usually thickened and dilated. The liver is carefully retracted superiorly. The ascending colon and the hepatic flexure of the colon are mobilized medially and downwards to expose the dilated duodenum. The duodenum is then adequately mobilized and freed from its retroperitoneal attachments – Kocher manoeuvre. Great care must be exercised not to dissect or manipulate either segment of the duodenum medially, to avoid injury to the ampulla of Vater or the common bile duct. The tube in the stomach is then passed distally into the dilated duodenum and helps to locate the point of obstruction and determine if a “windsock” abnormality is present. The type of atresia as well as any pancreatic abnormality (annular pancreas) or the presence of a rare preduodenal portal vein are noted. In patients with an annular pancreas, the pancreatic tissue should never be divided and should be bypassed.The duodenum distal to the site of obstruction is small and decompressed. The requirements for distal mobilization vary according to the location of the atresia and to the gap between the two segments. If necessary, the ligament of Treitz is divided, and mobilization and displacement of the distal duodenum is performed behind the superior mesenteric vessels, thus allowing a satisfactory anastomosis to be performed without any tension.
Duodenoduodenostomy is the procedure of choice for patients with duodenal atresia, stenosis and annular pancreas. The two surgical techniques, either side-to-side duodenoduodenostomy or proximal transverse to distal longitudinal – “diamond-shape” anastomosis – may be performed. Diamond-shaped duodenoduodenostomy has been reported to allow earlier feeding, earlier discharge and good long-term results.With two traction sutures, the redundant wall of the proximal duodenum is pulled downward to overlie the proximal portion of the distal duodenal segment. A transverse incision is made in the distal end of the proximal duodenum and a longitudinal incision is made in the smaller limb of the duodenum distal to the occlusion. These are made in such a position as to allow good approximation of the openings without tension. The papilla of Vater is located by observing bile flow. This is performed by gentle compression of the gall bladder. The orientation of the sutures in the diamondshape anastomosis and the overlapping between the proximal transverse incision and the distal longitudinal incision are shown. At this stage a small Nelaton catheter is passed distally through the opening made in the distal segment. 20–30 ml of warm saline is injected to rule atresias distally. The catheter is then removed.
A single layer anastomosis using interrupted 5/0 or 6/0 Vicryl sutures with posterior knots tied inside the posterior wall of the anastomosis and interrupted sutures with anterior knots tied outside the anterior wall. Before completion of the anterior part of the anastomosis, a transanastomotic feeding tube (
After abdominal exploration and the diagnosis of duodenal web (identified by the advancement of the gastric tube into the proximal dilated duodenum) two stay sutures are placed at the anterior dilated duodenal wall. A longitudinal incision of 2.5–3 cm is performed above the “transitional zone” between the wide and the narrow segments of the duodenum,and the duodenum is opened.
Two other stay sutures are placed at the margins of the duodenal incision. The windsock duodenal web must be clearly identified because the visible transition from the distended proximal duodenum to the small downstream duodenum may be several centimetres distal to the base of the web. Traction applied at the apex of the web deforms the duodenum at its point of attachment and allows excision at the base. The duodenal membrane is usually localized in the second part of the duodenum and occasionally in the third portion. It can be complete or with a central hole.Anatomically, the ampulla ofVater may open directly into the medial portion of the web itself – anteriorly, posteriorly, or with dual openings into the membrane – or it may open close to it. Thus, the close relationship of the membrane to the papilla ofVater makes its identification mandatory, before excision of the web. A single 4/0 Vicryl stay suture is placed at the centre of the membrane. The web is opened along the lateral side of the membrane and excision from the duodenal wall takes place, leaving a rim of tissue of 2–3 mm. The medial portion of the membrane should remain intact, thus avoiding damage to the ampulla of Vater. An intermittent bile flow is usually seen via the papilla of Vater indicating to the surgeon the exact line of excision.
Then the resection line is over sewn using interrupted 5-0 absorbable sutures. The duodenum is then closed transversely with interrupted sutures.Because of the pitfalls in cases of lax membrane that may bulge downwards distally into the distended duodenum (the so-called windsock phenomenon), and in order to avoid missing the anomaly, the patency of the distal duodenum must be identified by inserting a catheter through the duodenotomy before its closure. Following completion of the web resection and closure of the duodenum, the abdominal cavity is irrigated with 50 ml sterile warm saline. The wound is closed in layers: the peritoneum and the posterior fascia and the anterior fascia by two layers using continuous 4/0 Dexon or Vicryl sutures. The skin is closed with a running intracuticular suture using 5/0 Vicryl or Dexon suture. A nasogastric tube is left in place for post-operative gastric drainage. A gastrostomy may be performed if the need is anticipated. Intravenous therapy and antibiotics are continued post-operatively. The patient is kept without oral intake until stool is passed and limited clear or pale-green gastric drainage is noted (<1 ml/kg per h). The commencement of oral feeding may be delayed for several days and occasionally for 2 weeks or more. Post-operatively, patients may have a prolonged period of bile-stained aspirate, which is mainly due to the inability of the markedly dilated duodenum to produce effective peristalsis.Many surgeons therefore use transanastomotic tubes for feeding in the early post-operative period.
Complications. An anastomotic leak, injury to the bile duct, and sepsis are early complications. Late complications include peptic ulceration secondary to alkaline reflux, blind-loop syndrome with duodenal stasis, abdominal pain, diarrhea, and recurrent obstruction.
The prognosis is good for patients with a repaired duodenal stenosis or atresia; however, coexisting diagnoses, such as Down syndrome and cardiac anomalies, affect the outcome.
2.4. Ladd’s syndrome
Malrotation is congenital abnormal positioning of the midgut. Intestinal development is traditionally described as a process of elongation, rotation and fixation. The process begins in the fifth week of gestation. Elongation of the bowel exceeds abdominal cavity expansion and the bowel herniates from the abdomen. As the bowel returns to the abdomen, it rotates 270° anticlockwise around the superior mesenteric artery (SMA). Rotation is completed by week 10 of gestation, with the SMA contained within a broad mesenteric base attachment. The distal duodenum comes to lie across the midline towards the left upper quadrant, attached by the ligament of Treitz at the duodeno-jejunal (D-J) flexure to the posterior abdominal wall. The caecum passes to the right and downwards and becomes fixed to the posterior abdominal wall. This latter process may be incomplete at birth giving rise to a “high” caecum, a variant of normal in the neonate. The commonest features of malrotation are: (1) the D-J flexure lies right of midline, (2) the dorsal mesenteric attachment is narrow, and (3) peritoneal folds cross from colon and caecum to duodenum, liver and gallbladder (Ladd’s bands), thus possibly obstructing the duodenum.Whether Ladd’s bands are substantial enough to cause mechanical obstruction is debatable. The narrowed mesenteric base can lead to midgut volvulus, bowel obstruction and mesenteric vessel occlusion. Antenatal volvulus can result in bowel atresia.
Malrotation is estimated from autopsy studies to occur in 0.5–1% of the population, although only
Acute bowel obstruction due to Ladd’s bands or intermittent midgut volvulus can present with vomiting, typically bilious, as the commonest presenting feature accompanied by colicky abdominal pain and abdominal distention.An infant with abdominal tenderness and blood per rectum is suggestive of bowel ischaemia due to midgut volvulus. Older children without acute volvulus more often present with chronic episodic obstructive symptoms, failure to thrive, malabsorption, diarrhoea and non-specific colicky abdominal pain. Up to 10% of diagnoses of malrotation are made as an incidental finding. Plain abdominal radiograph is ofteormal but features suggestive of malrotation with or without midgut volvulus are a distended stomach and proximal duodenum with a paucity of gas distally, either throughout or unilaterally.An upper gastrointestinal contrast study is the investigation of choice for any child presenting with bilious vomiting and should be performed urgently. Findings in malrotation are: (1) D-J flexure right of left vertebral pedicle and/or inferior to pylorus, (2) the duodenum passes caudally and anteriorly, and (3) contrast tapering or a “corkscrew” appearance suggests obstruction and/or volvulus. In a recent series, sensitivity and specificity of this test were 92% and 20%, respectively. Caecal position is highly variable and may be normal in up to 15% of cases of malrotation.Contrast enema is therefore not always helpful. Abdominal ultrasound may show reversal in the relationship of SMA to superior mesenteric vein (SMV). In a normal situation the SMV is located to the right of the SMA, while SMV to the left of the artery is suggestive of malrotation.
All symptomatic patients with positive investigative findings should undergo urgent laparotomy. Management of the asymptomatic patient is more controversial. The risk of bowel ischaemia due to midgut volvulus is invariably present and the majority of surgeons would proceed to prompt operation. The principles of the procedure have remained almost unchanged since originally described by Ladd in 1936. The patient is positioned supine, legs extended. A right upper quadrant transverse incision is made. The umbilical vein is divided and ligated. The peritoneal fluid is examined. Frequently it is clear; bloodstained fluid implies bowel ischaemia and volvulus; faecal staining indicates bowel perforation and should be cultured.
The midgut is delivered from the wound and the base examined. Any volvulus should be derotated anticlockwise, noting the number of turns. The bowel is examined for viability and any ischaemic bowel should be wrapped in a damp swab and re-examined after 5–10 min. Non-viable bowel is resected and a primary anastamosis formed. If extensive ischaemic bowel of doubtful viability is present, a second-look laparotomy is performed after 24 h with the aim of minimizing the extent of bowel resection required. Ladd’s bands are divided.
The SMA is identified and mesenteric base broadened as much as possible by division of the peritoneal folds. Care must be takeot to injure the superior mesenteric vessels. The abnormal position of the appendix may cause diagnostic problems in future and, therefore, removal is advocated. The bowel is replaced with the duodenum to the right and the caecum in the left upper quadrant. The abdomen is closed. The nasogastric (NG) tube is aspirated hourly for the first 24 h. Intravenous fluids are continued postoperatively and NG tube fluid loss is replaced, millilitre for millilitre,with normal saline and potassium chloride (20 mmol/l saline). Enteral feeds are restarted when aspirates are clear and reducing in volume, usually after 24 h.
Laparoscopy may be used ion-acute cases of malrotation without volvulus, e.g., in incidentally diagnosed malrotation. The patient is positioned supine with the legs abducted. The surgeon stands between the patient’s feet with the assistant to the left of the patient. The umbilical port is placed first. A periumbilical incision is made. The midline fascia is held in two arterial clips, one on either side of the midline. The linea alba is divided and a 5- or 10-mm port placed into the abdominal cavity under direct vision. The port is secured with a purse-string and the ends of the sutures attached to an anchor on the port. Carbon dioxide is insufflated via the port until a final intra-abdominal pressure of 8–10 mmHg is reached in an infant, or 10–12 mmHg in an older child.During insufflation the abdomen is palpated and percussed to ensure adequate pneumoperitoneum is achieved. The flow rate of carbon dioxide is set between 0.5 and 1.5 l/min. The laparoscope is then inserted into this port. Two further 5-mm ports are placed under direct camera vision – left lower quadrant and right lower quadrant.Non-traumatic grasping forceps are inserted into these ports to manipulate the bowel.
The anatomy is defined and Ladd’s bands identified.Care must be taken to correctly identify landmarks such as the duodenum and ascending colon. To gain access to the duodenum, it is useful to raise the head of the operating table and elevate the right flank. The ascending colon falls towards the left side of the abdomen. The duodenum is exposed and Ladd’s bands are divided using either an ultrasonic blade or a combination of sharp dissection and electrocautery.After division, the bowel is examined along its length for any further causes of obstruction. The root of the mesentery is broadened by dividing the peritoneal folds. Care must be taken iot injuring the superior mesenteric vein. Appendicectomy is carried out either using an endoloop for intracorporeal ligation or by delivering the appendix through a trocar site and excising it extra-abdominally in smaller patients. Trocar sites are closed.
Conclusion.The outcome of patients undergoing Ladd’s procedure for isolated malrotation is very good and the majority make a full recovery. The commonest postoperative complication is adhesional obstruction (3–5%). Midgut volvulus occurs in 45–65% of children with malrotation and still carries a mortality rate of 7–15%; necrosis of more than 75% of the midgut is associated with short bowel syndrome. Up to 18% of children with short bowel syndrome on long term total parenteral nutrition have an original diagnosis of midgut volvulus.
2. Congenital anomalies that cause SMALL BOWEL obstruction in children
2.1. Atresia and stenosis of the small intestine.
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Etiology. Many theories exist regarding the etiology of jejunoileal atresias. Puppies, ewes, rabbits, and chick embryos have all been successfully used as models for intestinal atresia. To date, the most accepted theory regarding the etiology of jejunoileal atresia is that of an intrauterine vascular accident resulting iecrosis of the affected segment with subsequent resorption.
Classification. The 2 broad categories of jejunoileal defects are stenoses and atresias. A stenosis has an intact mesentery and is a localized narrowing of the bowel. No loss of continuity of the lumen exists, and the stenotic portion generally has an irregular muscularis and thickened submucosa. Four types of jejunoileal atresias were originally described, and recently, a subtype has been added. The different types represent variations of bowel loss severity and defect, from web to full atresia. This classification system generally guides prognosis and therapy
Atresias
Type I: In type I atresias, the mucosa and submucosa form a web or intraluminal diaphragm, resulting in obstruction. A windsock effect may be evident secondary to an increase in intraluminal pressure in the proximal bowel causing a prolapse of a portion of the web into the distal part of the bowel. A mesentery defect is not present, and the bowel length is not shortened.
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Type II: The mesentery is intact in type II atresias; however, the bowel is not joined. The dilated proximal portion has a bulbous blind end connected by a short fibrous cord to the blind end of the distal flattened bowel. The overall length of the small bowel is not usually shortened.
Type IIIa: The defect in type IIIa is similar to that in type II in that both types have blind proximal and distal ends; however, in type IIIa, complete disconnection exists. In addition, a V-shaped mesenteric defect is present. The proximal blind end is usually markedly dilated and not peristaltic. The compromised bowel undergoes intrauterine absorption, and as a result, the bowel in this category is variably shortened.
Type IIIb: In addition to a large defect of the mesentery, the bowel is significantly shortened. This lesion is also known as Christmas tree deformity because the bowel has the appearance of the tinsel coil wrapped around a single perfusing vessel, or Christmas tree . It has also been called an apple peel deformity. The distal ileum receives its blood supply from a single ileocolic or right colic artery because the better part of the superior mesenteric artery is absent. Prematurity, malrotation, and subsequent short bowel syndrome have been linked to this deformity, with increased morbidity and mortality rates.
Type IV: Type IV involves multiple small-bowel atresias of any combination of types I to III. This defect often takes on the appearance of a string of sausages because of the multiple lesions. The cause is unknown, and theories range from multiple ischemic infarcts to an early embryologic defect of the GI tract to an inflammatory process occurring in utero.
Diagnosis
Prenatal diagnosis of jejunoileal lesions by means of ultrasonography and prenatal screening is possible. Whereas associated anomalies are found in 30% of neonates with duodenal atresias, associated anomalies are found in 10% of neonates with jejunoileal atresias
Neonates with a proximal atresia develop bilious emesis within hours, whereas patients with more distal lesions may take longer to begin vomiting. A normal or scaphoidlike abdomen in a neonate with bilious emesis should be considered indicative of a proximal obstruction until proven otherwise. Abdominal distension is more pronounced with distal lesions.
Radiography is helpful to confirm the diagnosis. With more proximal atresias, few air-fluid levels are evident with no apparent gas in the lower part of the abdomen. The more distal lesions demonstrate more air-fluid levels, but the lower part remains without a gas pattern. Although a plain radiograph can depict the presence of an obstruction, it is not the best method of showing the location of the abnormality. A barium enema may be used to define a microcolon indicative of a distal small-bowel obstruction; it is also capable of establishing the diagnosis of other causes of lower obstruction, such as Hirschsprung disease or a meconium plug. The contrast enema may also reflux into the small bowel and help define the level of a distal obstructioт.
Stenosis in a neonate is more difficult to diagnose, and it may not manifest for some time. The clinical presentation is dependent on the severity of disease, and these patients have a history of intermittent emesis and failure to thrive. An upper GI with small-bowel follow-through is indicated in these patients.
Treatment
Preoperative care should be the same as that described for repair of duodenal lesions. Once the diagnosis is made, the patient should be fully resuscitated before surgical correction is attempted unless a perforation or volvulus is suspected. Urine output is closely monitored. Gastric decompression and thermoregulation are also essential. Preoperative antibiotics are administered.
In the operating room, a transverse supraumbilical incision affords adequate exposure of the abdominal contents. The full length of the bowel is manually explored for malrotation, other atresias, or stenoses; care is taken to keep the bowel moist and protected at all times. Malrotation should be corrected with a Ladd procedure. The length of intestine that appears functional is measured along the antimesenteric border because bowel length affects the procedure and overall prognosis. Sodium chloride solution is injected into the distal bowel and followed closely to the cecum to ensure patency. The same is done for the colon.
Once patency of the entire length of the bowel is established, the repair may proceed. The dilated proximal bulb generally does not have normal function and, as a result, should be resected up to a more suitable size to avoid problems with abnormal peristalsis postoperatively. If the bowel length is limited, a tapering enteroplasty should be considered rather than resection. An end-to-end anastomosis can then be performed.
The atretic region and the adjacent distended proximal and collapsed distal bowel are isolated with sterile moist swabs. The intestinal content is milked backwards into the stomach from where it is aspirated and a bacteriology swab is sent for culture and sensitivity.Alternatively,proximal bowel contents are milked into the bulbous blind end if it is to be resected. An atraumatic bowel clamp is then placed across the bowel a few centimetres proximal to the elected site for transection. If total bowel length is deemed of adequate length (>
With type III(b) or high jejunal atresia the proximal bowel should be derotated and resection of the bulbous portion may be extended into the third or second part of the duodenum without jeopardizing the ampulla of Vater. The distal “apple peel” component of Type III(b) atresia may require release of restricting bands along the free edge of the distally coiled and narrow mesentery to avoid kinking and interference with the blood supply. The large mesenteric defect is usually left open but with proximal bowel resection the residual mesentery can be used to obliterate the defect. Furthermore, to prevent kinking of the marginal artery after completion of the anastomosis, the bowel needs to be replaced very carefully into the peritoneal cavity in a position of non-rotation.
The anastomosis is either end-to-end or end-to-back (Denis-Browne method); 5/0 or 6/0 absorbable sutures stitches are used. The mesenteric border of the divided ends is united with a stay suture and a matching stitch is placed at corresponding points of the anti-mesenteric borders of the divided ends. The “anterior” edges of the bowel are then united with interrupted through-and-through extramucosal stitches, which are tied on the serosal surface.
After completion of one-half of the anastomosis the bowel is rotated through 180° and the “posterior” anastomosis completed. Alternatively the posterior edge of the bowel is anastomosed with the stitches tied on the mucosal surface followed by anastomosis of the “anterior” edges with interrupted stitches tied on the serosal surface. The suture lines are inspected for anastomotic integrity or tested with saline injection on completion. Although isolated type I atresia is best dealt with by primary resection and anastomosis,multiple diaphragms have been successfully perforated with transluminal bougies being passed along the entire length of the affected small bowel.
Multiple type IV atresias, present in 18% of infants, are often localized necessitating en-bloc resection and a single anastomosis, rather than multiple anastomosis. It is important, however, to maintain maximum bowel length to avoid the short bowel syndrome. Similar techniques are used for intestinal stenosis and type I atresias. Procedures such as simple transverse enteroplasties, excision of membranes, bypassing techniques or side-to-side anastomosis are no longer utilized. They fail to remove the abnormal dysfunctional segments of intestine, thus increasing the risk of the blind loop syndrome.
The defect in the mesentery is repaired by approximating or overlapping the divided edges with interrupted sutures taking great care not to incorporate blood vessels or kinking the anastomosis. Closure of the large mesenteric defect can be facilitated by using the preserved mesentery of the resected proximal bowel.
_ Wound Closure. The peritoneal cavity is thoroughly irrigated with warm saline to remove all macroscopic debris and the bowel then returned to the abdominal cavity. Care is takeot to kink the anastomosis. The abdomen is closed by approximating en mass all the layers of the abdominal wall, excluding Scarpa’s fascia,with a single continuous 4/0 monofilament absorbable suture, followed by subcutaneous and subcuticular absorbable stitches. No drains or trans-anastomotic tubes are used.
Postoperatively, gastric drainage should continue until evidence indicates return of bowel function. Total parenteral nutrition (TPN) should be started shortly after surgery and continued until enteral feeds are tolerated. The baby must be closely monitored after surgery; monitor abdominal girth, vital signs, temperature, fluid status, urine output, gastric drainage, and level of activity.
The prognosis for patients with jejunoileal atresia is dependent on the amount of residual functional bowel that exists after surgery. In general,
2.2. Meconium ileus.
Meconium ileus (MI) is among the most common causes of intestinal obstruction in the newborn, accounting for 9-33% of neonatal intestinal obstructions. MI is the earliest clinical manifestation of cystic fibrosis (CF) and occurs in approximately 16% of patients with CF, although MI also occurs in patients who do not have CF.
Genetic causes of cystic fibrosis. CF is an autosomal recessive disease; its estimated heterozygote frequency in white people is
Pathophysiology. Meconium in patients with MI has higher protein and lower carbohydrate concentration than that in control populations. In 1958, Green, Clarke, and Schwachman found that albumin was the major protein present in the meconium of infants with MI. Addition of albumin to normal meconium makes it viscid; addition of pancreatic protease liquefies the viscid mass. This led to the belief that pancreatic insufficiency played a central role in MI pathogenesis.
Abnormal intestinal motility also may contribute to MI development. Some patients with CF have prolonged small intestinal transit times. Non-CF diseases associated with abnormal gut motility (eg, Hirschsprung disease, chronic intestinal pseudo-obstruction) have been associated with MI-like disease, suggesting that decreased peristalsis may allow increased resorption of water, thus favoring MI development.
Postnatally, intestinal disease is characterized by a glandular abnormality that produces hyperviscous mucus. How mutations of the CF gene generate abnormal mucins is not fully described, nor is the developmental sequence of mucin secretion in the fetal intestine, although the CFTR ion channel defect possibly leads to dehydration of intraluminal contents. The meconium of fetuses with CF and MI has increased viscosity and decreased water content compared to normal controls.
Clinical signs
Simple MI usually presents with abdominal distension at birth, eventually progressing to failure to pass meconium, bilious vomiting, and progressive abdominal distension. Often, examination reveals dilated loops of bowel with a doughy character that indent on palpation. The rectum and anus usually are narrow, a finding possibly misinterpreted as anal stenosis.
Complicated MI presents more dramatically at birth with severe abdominal distension, sometimes accompanied by abdominal wall erythema and edema. Abdominal distension may be severe enough to cause respiratory distress. Signs of peritonitis include tenderness, abdominal wall edema, distension, and clinical evidence of sepsis. A palpable mass may indicate pseudocyst formation. Often, the neonate is in extremis and needs urgent resuscitation and surgical exploration.
CF is characterized clinically by the following triad:
ü Chronic obstruction and infection of the respiratory tract
ü Exocrine pancreatic insufficiency
ü Elevated sweat chloride levels
Imaging Studies.
Ultrasound evaluation. Prenatal sonographic characteristics associated with MI include hyperechoic masses (ie, inspissated meconium in the terminal ileum), dilated bowel, and inability to visualize the gallbladder.
Abdominal x-ray. In uncomplicated MI, abdominal radiography reveals a characteristic pattern of unevenly dilated loops of bowel with variable air-fluid levels. Air-fluid levels may be absent due to the viscid, non-liquid nature of the inspissated meconium. Bubbles of gas may become evident as air mixes with the tenacious meconium. While this soap-bubble appearance depends on the viscosity of the meconium and is not a constant feature, this radiographic feature is pathognomonic and distinguishes MI from other causes of newborn intestinal obstruction. Although none of these features alone is diagnostic for MI, they strongly suggest the diagnosis when combined with a family history of CF.
Radiologic findings in complicated MI vary, based upon the associated complication. Speckled calcification visible on abdominal plain films strongly suggests intrauterine intestinal perforation and meconium peritonitis. Visible obstruction and a large dense mass with a rim of calcification suggest a pseudocyst.
· When MI is suspected based on clinical and radiographic evidence, a contrast barium enema may be performed for diagnosis. If MI is likely, follow the contrast enema with a therapeutic Gastrografin enema. Some physicians advocate water-
A diagnosis of CF should be confirmed or refuted by a sweat test. A sweat test may be performed any time after the first 48 hours of life if the neonate is not edematous. The minimum amount of sweat needed is either 75 mg, a quantity that may be difficult to obtain from young infants. Never pool sweat from multiple sites to obtain the required quantity because the rate of sweating determines electrolyte content. Value over 60 meq/L of sweat sodium or chloride are diagnostic.
Mutation analysis, performed on buccal or blood cells, helps confirm the diagnosis if it yields at least 1 known CF mutations.
Treatment
Medical therapy. Manage both simple and complicated MI iewborns as an intestinal obstruction. Perform resuscitative measures, including mechanical respiratory support, if necessary. Initiate intravenous hydration with gastric decompression, evaluate and correct any coagulation disorders, and begin empiric antibiotic coverage. Immediately obtain a surgical evaluation when MI is suspected or diagnosed.
Gastrografin enemas.
In 1969, Noblett introduced the use of Gastrografin enemas to treat 4 infants with MI. Variations on this approach are now the preferred initial method to treat uncomplicated MI.
Gastrografin is meglumine diatrizoate, a hyperosmolar, water-soluble, radiopaque solution containing 0.1% polysorbate 80 (Tween 80) and 37% organically bound iodine. The solution’s osmolarity is 1900 mOsm/L.
Noblett’s criteria for proceeding with this therapy require the following:
Ø The initial diagnostic contrast enema must exclude other causes of neonatal distal intestinal obstruction.
Ø The infant must show signs of uncomplicated MI and no clinical or radiologic evidence of complicating factors (eg, volvulus, gangrene, perforation, peritonitis, atresia of the small bowel).
Ø The infant should be well prepared for the enema, with adequate fluid and electrolyte replacement and correction of hypothermia.
Ø The enema must be performed under fluoroscopic control.
Ø Intravenous antibiotics should be administered.
Procedure.
Ø Upon instillation, fluid is drawn into the intestinal lumen to hydrate and soften the meconium mass. Both transient osmotic diarrhea and diuresis follow. Adequate resuscitation and hydration in anticipation of these fluid losses is paramount.
Ø Under fluoroscopic control, infuse a 25-50% solution of Gastrografin slowly at low hydrostatic pressure through a catheter inserted into the rectum. Avoid balloon inflation to minimize the risk of rectal perforation.
Ø To help deconcentrate the inspissated meconium, 1% N-acetylcysteine may be added to the enema solution. The procedure requires a slow infusion, carefully monitored under fluoroscopy.
Ø Obtain radiographs in 8-12 hours, or as clinically indicated, to confirm evacuation of the obstruction and to exclude late perforation.
Ø If necessary, serial Gastrografin enemas can be performed at 6- to 24-hour intervals.
Ø Surgical exploration is indicated for patients with progressive distension, signs of peritonitis, or clinical deterioration.
Ø Following successful evacuation and resuscitation, Noblett suggests administering a 10% N-acetylcysteine solution (5 mL q6h) through a nasogastric (NG) tube to liquefy upper GI secretions.
Ø Feedings, including supplemental pancreatic enzymes for infants with confirmed CF, may be initiated when signs of obstruction have subsided, usually within 48 hours.
Potential complications.
· Perforation.
· Hypovolemic shock is a profound risk when delivering hypertonic enemas.
Ischemia caused by overdistension is worsened by hypoperfusion; this hypoperfusion is caused by the hypovolemia that results from poor fluid resuscitation.
Surgical therapy. A number of surgical approaches to treat uncomplicated MI have been proposed over the years; variable success rates have been achieved. Individualize the approach for each infant.
The goal of operative management in simple uncomplicated MI is to evacuate meconium from the intestine while preserving maximal intestinal length.
Surgery always is indicated for complicated MI. Complicated MI requires resection more often than simple MI and always requires temporary stomas.
Only 6% to 10% of uncomplicated forms fail the nonoperative management using a water-soluble contrast enema. If no significant difference in intestinal diameters and no microcolon is present, a limited enterotomy and repeated warm saline irrigations through a smooth catheter provide for the best result. Meconium discharge may be manually supported, using an enterotomy placed in the dilated hypertrophic ileum. The catheter is two-way directed with care, clearing the small as well as the large bowel.After exclusion of an atretic intestinal segment, the enterostomy is closed by single interrupted seromuscular stitches.
In contrast, approximately half of neonates with meconium ileus cannot be treated adequately with irrigations and/or present additionally an intestinal obstruction complicated by neonatal intestinal perforation or ileal atresia secondary after intrauterine perforation.
They always require a surgical procedure such as resection of the dilated meconium-filled ileum and ileal anastomosis (as shown in Chap. 22).Additionally, complicated cases of meconium ileus are seen in newborns with an extreme difference in diameters of the proximal and distal ileum, and a significant microcolon. In those cases, the double-tube ileostomy technique according to Rehbein has proved to be an effective treatment and avoids the secondary laparotomy for stoma closure. A horizontal predominantly right-sided laparotomy, approximately
A small transverse incision into the enlarged ileum is performed, approximately 5–7 cm in front of the narrow part filled with stool pellets. Four stay sutures are inserted into the margins of the incision. If an atresia exists, the atretic part is resected and the thickened meconium from the proximal part and the grey stool pellets from the distal part are evacuated by numerous irrigations with warm saline through a 5–8 Ch feeding tube supporting the manoeuvre by gentle manual forward and backward manipulation.
Once all intestinal contents are evacuated, a 10 Ch feeding tube with larger cut openings is inserted through the enterotomy in the proximal non-dilated ileum, and a second 5 Ch tube is inserted into the distal narrow ileum or microcolon in a T-tube fashion. The enterotomy is closed around the tubes and is tightly fixed to the appropriate part of the ventral abdominal wall – in a similar fashion as in a gastrostomy. Both tubes are carefully fixed with nonabsorbable sutures to the skin. If a bowel segment had to be resected, the stoma for the tubes is best situated approximately
Different surgical techniques have been developed in the past consisting of a resection of the enlarged bowel segment and temporary decompression by means of a distal or proximal enterostomy. The most simple form is a double-barrelled ileostomy according to Mikulicz, with the two loops brought out sideto– side. This solution is quick and avoids an intra-abdominal anastomosis. More technical alternatives have been described thereafter: a distal ileostomy with end-to-side ileal anastomosis (Bishop-Koop) has been called “distal chimney enterostomy”. This procedure consists of a Roux-en-Y anastomosis between the end of the proximal segment and the side of the distal segment, at least 3 to
This technique should facilitate irrigation as well as decompression of the proximal small bowel. The enterostomies can be closed by an end-to-end anastomosis when uninhibited passage of intestinal contents is established, mostly between 7 and 12 days after.
When a terminal ileostomy or colostomy is desired ieonates and/or children, the preferred method used is the nipple-valve system formation. This is an easy technical procedure and avoids any kind of infiltration or stricture or retraction of the neostoma. A 2- to 3-cm-long intestinal segment is used with a serosal surface free of fat and with a good vascular supply. Seromuscular wall is sutured to the fascia in four quadrants. Next the stitch is taken through the skin seromuscular wall and edge of the stoma, thereby creating the nipple. Four to six sutures are normally needed depending upon the size of the stoma.
Nutritional management. Infants with uncomplicated MI and CF may receive breast milk or routine infant formula, enzymes, and vitamins.
Patients who have a complicated surgical course require either continuous enteral feedings or total parenteral nutrition (TPN).
Complications
Infants with MI are at risk for cholestasis, particularly if they have received or are receiving TPN. Monitor alkaline phosphatase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin levels weekly.
Infants who have had significant bowel resection (ie, >33%) may be difficult to manage, especially if the ileocecal valve has been resected. In addition, an ileostomy may lead to excessive fluid and sodium losses.
Gastric acid hypersecretion occurs in patients with short-bowel syndrome. Histamine 2 receptor blockers may be used as an adjunct to pancreatic enzyme therapy in patients who have had significant bowel resections.
Pulmonary complications. Although clinical lung disease usually does not develop early, mucus plugging and atelectasis can occur. Immediately postoperatively, initiate vigorous prophylactic pulmonary care with chest physiotherapy. Do not use the head-down position because this increases the risk of gastroesophageal reflux and aspiration. Prophylactic antibiotics are unnecessary. Antibiotic therapy, if needed, should be based on respiratory tract cultures.
3. Congenital anomalies that cause LARGE BOWEL obstruction in children
3.1. Atresia and stenosis of the large intestine.
Incidence
Colonic atresia is a rare disorder of the newborn. The incidence is estimated at one per every 20,000 to 40,000 live births. It is the least common intestinal atresia accounting for only 5-10% of reported cases.
Etiology
Although the exact etiology of colonic atresia is unknown, it is believed by many to result from in-utero vascular occlusion of the large bowel.
Clinical Presentation
Infants with colonic atresia present within the first 24 hours of life with abdominal distension, bilious vomiting, and failure to pass meconium. Intestinal loops are often both visible and palpable through the distended abdominal wall. On rare occasions, infants with colonic atresia present very ill with volvulus or with peritonitis secondary to perforation of the proximal dilated bowel. The differential diagnosis includes malrotation with volvulus, small bowel atresia, meconium disease, and Hirschprung’s disease. Drug-induced ileus, megacystis hypoperistalsis syndrome, and hypoplastic left colon are other conditions to consider. Colonic atresia has been reported in infants with Hirschsprung’s disease, small intestinal atresias, abdominal wall defects (i.e., gastroschisis, omphalocele), anorectal malformations, and other major anomalies ( renal, cardiac, ocular). Polydactyly and syndactyly are also associated with colonic atresia.
Diagnosis
Abdominal films demonstrate air-fluid levels and often a huge dilated loop just proximal to the obstruction. Barium enema shows a small unused colon that ends abruptly at the level of obstruction before refluxing in the small bowel. If associated with a small bowel atresia, the diagnosis is ofteot made until laparotomy.
Classification
The classification of colonic atresias is the same as that of small intestinal atresias. An intraluminal membrane obstructing an otherwise intact colon wall is a Type I lesion. In type II lesions, the bowel segments remain connected via a cord-like band and there is no mesenteric defect. Type III atresias lack a connection between the bowel segments and often have large mesenteric defects. Atresias isolated to the colon are equally distributed by type and location. However, type III atresias are the most common lesions if ileocolonic atresias are also included. Type IV lesions contain multiple atresias.
Treatment
The infant should be brought to the operating room euvolemic and normothermic. At operation, proximal and distal atresias should be identified (Fig. 62.1) and colonic biopsies taken to assess for the presence of Hirschsprung’s disease (aganglionosis). In infants with Hirschsprung’s disease, a leveling colostomy should be performed. Infants without Hirschsprung’s disease can be managed in one of two ways. In one method, the proximal bulbous tip is either resected or tapered and a primary anastomosis is performed. Alternatively, an end colostomy can be performed.
3.2. Hirschsprung’s disease.
Hirschsprung disease is characterized by a congenital absence of ganglion cells in the distal colon resulting in a functional obstruction.
Causes. Although the precise mechanism responsible for Hirschsprung disease is unknown, the following basic theories have been proposed: (1) the neuroblasts fail to migrate into the affected segments of bowel; (2) the neuroblasts that were once present fail to mature; or (3) normal development of the cells occurs, but some insult leads to degradation or destruction of the cells.
Pathophysiology. Congenital aganglionosis of the distal bowel defines Hirschsprung disease. Aganglionosis begins with the anus, which is always involved, and continues proximally for a variable distance. Both the myenteric (Auerbach) and submucosal (Meissner) plexus are absent, resulting in reduced bowel peristalsis and function. The precise mechanism underlying the development of Hirschsprung disease is unknown.
Three neuronal plexus innervate the intestine: the submucosal (ie, Meissner) plexus, the intermuscular (ie, Auerbach) plexus, and the smaller mucosal plexus. All of these plexus are finely integrated and involved in all aspects of bowel function, including absorption, secretion, and motility.
Normal motility is primarily under the control of intrinsic neurons. Bowel function is adequate, despite a loss of extrinsic innervation. These ganglia control both contraction and relaxation of smooth muscle, with relaxation predominating. Extrinsic control is mainly through the cholinergic and adrenergic fibers. The cholinergic fibers cause contraction, and the adrenergic fibers mainly cause inhibition.
In patients with Hirschsprung disease, ganglion cells are absent, leading to a marked increase in extrinsic intestinal innervation. The innervation of both the cholinergic and adrenergic systems is 2-3 times that of normal innervation. The adrenergic (excitatory) system is thought to predominate over the cholinergic (inhibitory) system, leading to an increase in smooth muscle tone. With the loss of the intrinsic enteric inhibitory nerves, the increased tone is unopposed and leads to an imbalance of smooth muscle contractility and a functional obstruction.
Frequency. Hirschsprung disease occurs at an approximate rate of 1 case per 5400-7200 newborns.
Mortality/Morbidity. Untreated aganglionic megacolon in infancy may result in a mortality rate of as much as 80%. Operative mortality rates for any of the interventional procedures are very low. Even in cases of treated Hirschsprung disease, the mortality rate may be as much as 30% as a result of enterocolitis.
Age. The age at which Hirschsprung disease is diagnosed has progressively decreased over the past century. In the early 1900s, the median age at diagnosis was 2-3 years; from the 1950s to 1970s, the median age was 2-6 months. Currently, approximately 90% of patients with Hirschsprung disease are diagnosed in the newborn period.
Clinical signs
History. Hirschsprung disease should be considered in any newborn with delayed passage of meconium or in any child with a history of chronic constipation since birth. Other symptoms include bowel obstruction with bilious vomiting, abdominal distention, poor feeding, and failure to thrive. Older children with Hirschsprung disease have usually had chronic constipation since birth. They may also show evidence of poor weight gain.
Despite significant constipation and abdominal distension, children with Hirschsprung disease rarely develop encopresis. In contrast, children with functional constipation or stool-withholding behaviors more commonly develop encopresis.
Physical. Physical examination in the newborn period is usually not diagnostic, but it may reveal a distended abdomen and/or spasm of the anus. A low imperforate anus with a perineal opening may have a similar presentation to that of a patient with Hirschsprung disease. Careful physical examination differentiates the two. In older children, however, a distended abdomen resulting from an inability to release flatus is not uncommon.
Diagnosis
Plain abdominal radiographs may show distended bowel loops with a paucity of air in the rectum.
Barium enema. Avoid washing out the distal colon with enemas before obtaining the contrast enema because this may distort a low transition zone. Radiographs are taken immediately after hand injection of contrast and again 24 hours later. A narrowed distal colon with proximal dilation is the classic finding of Hirschsprung disease after a barium enema.
However, findings ieonates (ie, babies aged <1 mo) are difficult to interpret and often fail to demonstrate this transition zone, which takes time to develop.
Another radiographic finding suggestive of Hirschsprung disease is the retention of contrast for longer than 24 hours after the barium enema has been performed.
Anorectal manometry. Anorectal manometry detects the absence of the relaxation reflex of the internal sphincter after distension of the rectal lumen.
Because cardiac malformation (2-5%) and trisomy 21 (5-15%) are associated with congenital aganglionosis, cardiac evaluation and genetic testing may be warranted.
Rectal biopsy. The definitive diagnosis of Hirschsprung disease is confirmed by rectal biopsy, ie, findings that indicate an absence of ganglion cells. The definitive method for obtaining tissue for pathologic examination is by a full-thickness rectal biopsy. The specimen must be obtained at least
The abdomen is opened via the Pfannenstiel incision. The biopsy site is selected by observing the apparent transitional zone. In the usual case of rectosigmoid aganglionosis, three seromuscular biopsies are taken along the antimesenteric surface without entering the lumen. One biopsy is taken from the narrowed segment of bowel, a second biopsy from the transition zone and a third biopsy from the dilated portion above the transition zone.Biopsies are assessed intra-operatively by frozen section, to determine the level of ganglionic bowel.
Treatment
Medical Care. The general goals of medical care are to treat the complications of unrecognized or untreated Hirschsprung disease, to institute temporary measures until definitive reconstructive surgery can take place, and to manage bowel function after reconstructive surgery.
Management of complications of recognized aganglionosis is directed toward reestablishing normal fluid and electrolyte balance, preventing bowel overdistension (with possible perforation), and managing complications such as sepsis.
Intravenous hydration, nasogastric decompression, and, as indicated, administration of intravenous antibiotics remain the cornerstones of initial medical management.
Colonic lavage, consisting of mechanical irrigation with a large-bore rectal tube and large volumes of irrigant, may be required.
Balanced salt solutions may help prevent electrolyte imbalances.
Colonic lavage may also be used in postoperative patients who develop enterocolitis as a complication. Injecting the nonrelaxing internal sphincter mechanism with botulinum toxin (Botox) has recently been shown to induce more normal patterns of bowel movements in postoperative patients with enterocolitis.
Surgical Care. Surgical management of Hirschsprung disease begins with the initial diagnosis, which often requires a full-thickness rectal biopsy. In most cases, treatment also includes creating a diverting colostomy at the time of diagnosis. Once the child grows and weighs more than
Typically, neonates diagnosed with Hirschsprung disease are first treated with a diverting colostomy. Identify the transition zone, and place the colostomy proximal to this area. The presence of ganglion cells at the colostomy site must be unequivocally confirmed by a frozen-section biopsy. A diverting colostomy may also be required in older patients to decompress the dilated proximal bowel and allow time for it to return to a normal caliber. Either a loop or end stoma is appropriate, usually based on the surgeon’s preference.
Many surgeons prefer right transverse colostomy; others advocate performing colostomy just above the transition to ganglionic bowel. Ileostomy is indicated in patients who have total colonic aganglionosis. A right transverse colostomy is convenient in usual cases. We perform a loop colostomy over a skin bridge.A V-shaped incision is made in the right upper quadrant. The V-skin-flap is reflected upwards. The external oblique is split and the internal oblique and transverse abdominis muscles are divided with diathermy. The peritoneum is opened.
An opening is made in the mesocolon of the selected segment of transverse colon. The skin flap is pulled through the opening in the mesocolon and sutured to the opposite skin margin. A few interrupted absorbable sutures of 4/0 or 5/0 are placed between the peritoneum, the muscle layers of abdominal wall and the seromuscular layer of colon. The colon is opened longitudinally along the antimesenteric border using diathermy. The bowel is sutured to the skin using interrupted 4/0 absorbable sutures.
The 3 most commonly performed repairs are the Swenson, Duhamel, and Soave procedures. Regardless of the pull-through procedure chosen, cleaning the colon prior to definitive repair is necessary.
The Swenson procedure was the original pull-through procedure used to treat Hirschsprung disease. The aganglionic segment is resected down to the sigmoid colon and the remaining rectum, and an oblique anastomosis is performed between the normal colon to the low rectum.
The Duhamel procedure was first described in 1956 as a modification to the Swenson procedure. Key points are that a retrorectal approach is used and a significant portion of aganglionic rectum is retained. The aganglionic bowel is resected down to the rectum, and the rectum is oversewn. The proximal bowel is then brought through the retrorectal space (between the rectum and sacrum), and an end-to-side anastomosis is performed on the remaining rectum.
The Soave procedure was introduced in the 1960s and consists of removing the mucosa and submucosa of the rectum and pulling the ganglionic bowel through the aganglionic muscular cuff of the rectum. The original operation did not include a formal anastomosis, but the procedure has been modified by Boley to include a primary anastomosis at the anus.
Diet. The patient should have nothing by mouth before the operation. Institute tube feeding or formula/breast milk once bowel function resumes. High-fiber diets and diets containing fresh fruits and vegetables may optimize postoperative bowel function in certain patients.
Activity. Limit physical activity for about 6 weeks to allow the wound to heal properly (applies more to older children).
Further Inpatient Care. If a diverting colostomy is created in a newborn, he or she must remain in the hospital until the ostomy is functioning and feeding goals are obtained. Feedings are usually initiated 24-48 hours after the creation of the colostomy.
After the definitive pull-through procedure is performed, the patient is hospitalized until full feedings are possible and evidence of the return of bowel function is obtained. Patients are to take nothing by mouth, with intravenous fluid hydration until they pass flatus or have a bowel movement. Once this occurs, clear liquids may be started, and the diet may be advanced until feeding goals are obtained. Intravenous antibiotics are also continued until evidence of proper bowel function is observed.
Complications. In general, the complications are anastomotic leak (5%), anastomotic stricture (5-10%), intestinal obstruction (5%), pelvic abscess (5%), and wound infection (10%).
3.3. Anorectal malformation.
Anorectal malformations comprise a wide spectrum of disease affecting boys and girls and can involve malformations of the distal anus and rectum, as well as the urinary and genital tracts.
Frequency. Anorectal malformations occur in approximately
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Male |
Female |
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High Anorectal agenesis With rectoprostatic urethral fistula Without fistula Rectal atresia |
High Anorectal agenesis With rectovaginal fistula Without fistula Rectal atresia |
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Intermediate Rectobulbar urethral fistula Anal agenesis without fistula |
Intermediate Rectovestibular fistula Rectovaginal fistula Anal agenesis without fistula |
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Low Anocutaneus fistula Anal stenosis |
Low Anovestibular fistula Anocutaneous fistula Anal stenosis |
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Cloaca |
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Rare Malformations |
Rare Malformations |
Decision-making in the newborn boy with anorectal anomalies
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In 80-90% of newborn boys, clinical evaluation and urinalysis provide enough information for the surgeon to decide whether the baby requires a colostomy.
After the baby is born, an intravenous line is placed for fluids and antibiotics. A nasogastric tube is inserted to keep the stomach decompressed to avoid the risk of vomiting and aspiration.
Meconium is not usually observed at the perineum in a baby with a rectoperineal fistula until at least 16-24 hours of life. Abdominal distension does not develop during the first few hours of life but is required to force meconium through a rectoperineal fistula, as well as through a urinary fistula. This is because the most distal part of the rectum in these children is surrounded by a funnellike voluntary muscle structure that keeps part of the rectum collapsed and empty. The intra-abdominal pressure must be high enough to overcome the tone of the muscles that surround the rectum if meconium is to be expected at the perineum or in the urine. Therefore, the decision of whether to perform a colostomy or an anoplasty must be delayed for 16-24 hours while the surgeon evaluates for clinical evidence of the baby’s anorectal anomaly.
Clinical inspection of the buttocks is important. A flat bottom or flat perineum, as evidenced by the lack of a midline gluteal fold and the absence of an anal dimple, indicates that the patient has very poor muscles in the perineum. These findings are associated with a high malformation; therefore, a colostomy should be performed.
Perineal signs found in patients with low malformations include the presence of meconium at the perineum, a bucket-handle malformation (ie, a prominent skin tag located at the anal dimple, below which an instrument can be passed), and an anal membrane (through which one can see meconium).
Newborn boys with rectoperineal fistula do not need a colostomy. They can undergo a posterior sagittal anoplasty.
Baby boys with evidence of a rectourinary tract communication should undergo fecal diversion with a colostomy.
If none of the clinical signs to determine the location of the anorectal anomaly are evident by 24 hours, performing a radiologic test can help. This situation is only necessary in approximately 10% of patients. Crosstable lateral radiography with the baby prone, with the pelvis elevated, and with a radiopaque marker placed on the perineum is performed. Rarely, radiography may show the column of air in the distal rectum to be within
Some authors have performed definitive repair in the newborn period. The advantage to this approach is avoidance of the colostomy and earlier repair of the malformation; however, with this practice, considerable risk to the urinary tract exists because the surgeon does not know the precise anorectal defect. The only way to determine the patient’s anorectal defect definitively is to perform distal colostography, which requires the presence of a colostomy. Without this information, an operation in the newborn period is essentially a blind perineal exploration. The surgeon may not be able to locate the rectum and may find and damage other unexpected structures, such as the posterior urethra, seminal vesicles, vas deferens, and ectopic ureters during the search for the rectum. Finally, without fecal diversion, the risk of dehiscence and infection exists. These complications may compromise the chance of achieving bowel function.
The exception, which is rare, occurs when the crosstable lateral radiograph taken at 16-24 hours shows that the rectum is located just below the coccyx. In this case, the rectum can be reached from the posterior sagittal approach.
Urinalysis and a gauze placement over the penis can be done to determine the presence of fecal matter in the urine, which is considered evidence of a rectourinary fistula.
Abdominal ultrasonography must be performed to evaluate for the presence of an obstructive uropathy. At the same time, spinal ultrasonography can be performed to evaluate for spinal anomalies, including the presence of a tethered cord.
Any method of trying to determine the location of the distal rectum before 16 hours of life is flawed because of the contracted state of the funnellike sphincter mechanism. Normally, the funnel-shaped muscle structure is contracted unless overcome with a distending force. Tests such as MRI, ultrasonography, computed tomography scanning, or injection of contrast through the perineum falsely locate the distal rectum as high.
Distal colostography (performed usually 1 mo after colostomy opening) must have adequate pressure to demonstrate a fistula from the rectum to the urinary tract or this method also falsely locates the distal rectum as high in the pelvis.
Once the patient recovers from colostomy and demonstrates good growth and development, the definitive operation can be planned for 4-8 weeks.
Decision-making in the newborn girl with anorectal anomalies
The decision of whether to perform colostomy in newborns girls is less complicated than iewborn boys. In 90% of patients, a meticulous perineal inspection demonstrates the anorectal defect. Waiting 16-24 hours for enough abdominal distension to demonstrate the presence of a rectoperineal fistula or rectovestibular fistula also applies to females.
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The most common anomaly in females is a rectovestibular fistula. Perineal inspection shows a normal urethra, normal vagina, and another orifice that is the rectal fistula in the vestibule.
Performing a diverting colostomy is the safest option for a surgeon without extensive experience in anorectal anomalies when faced with a baby who has clinical evidence of a rectovestibular fistula. Colostomy before the main repair avoids the complications of infection and dehiscence. Definitive repair of this anomaly in the newborn period should be reserved for surgeons who have significant experience repairing these defects. This anomaly has an excellent prognosis; therefore, complications that could affect future continence must be avoided.
Unfortunately, the most common referral for reoperations to tertiary centers that care for anorectal anomalies is for patients with rectovestibular fistulas who experienced failed primary repair in the newborn period. Occasionally, the fistulas are large enough to decompress the gastrointestinal tract, and they may be dilated to facilitate fecal drainage until the baby is older and a definitive repair is performed. Definitive repair involves a posterior sagittal approach. The most delicate part of this operation is the separation of the rectum and vagina, which share a common wall.
Like males, females can also have a rectoperineal fistula, which requires anoplasty to be performed in the newborn period.
Like in males, less than 5% of female babies have no clinical evidence of the location of the rectum after 24 hours. They may have imperforate anus with no fistula. Crosstable lateral radiography should be performed, which helps determine the need for a colostomy.
The presence of a single perineal orifice in a patient is clinical evidence of persistent cloaca. Patients with these anomalies also have small genitalia. In patients with persistent cloaca, examination of the abdomen may reveal an abdominal mass that likely represents a distended vagina (hydrocolpos), which is present in 50% of patients with persistent cloaca. Abdominal ultrasonography is helpful to determine the presence of an obstructive uropathy and hydrocolpos.
Unfortunately, a common error in diagnosis occurs during the perineal inspection when a female is thought to have imperforate anus with rectovaginal fistula; however, in actuality, all 3 structures (ie, urinary tract, vagina, rectum) meet in a common channel, and the baby has persistent cloaca. This misconception has important therapeutic implications that are discussed below.
Making the correct determination of persistent cloaca is vital because 90% of babies with persistent cloaca have an associated urologic problem and 50% have hydrocolpos. The urinary tract and the distended vagina both may need to be managed in the newborn period to avoid serious complications.
Missing the diagnosis of persistent cloaca frequently means that an obstructive uropathy is overlooked. The patient may then receive only a colostomy, and subsequently, sepsis, acidosis, and sometimes death may occur.
The other implication of missing the diagnosis of persistent cloaca involves repairing only the rectal component of the anomaly, leaving the patient with a persistent urogenital sinus.
