LARGE INTESTINE (COLON) EMBRYOLOGY

LECTURE 7

OPERATIVE SURGERY OF STOMACH AND LIVER

STOMACH

The stomach is the most dilated part of the digestive tube. It is approximately 10 inches long, 5 inches wide and has a normal capacity of about 2 pints. It is capable of great dilatation and may shrink into a more-orless tubular form when empty. At its upper part it is approximated to the diaphragm by the esophagus; at its lower end it is more-orless fixed because of its connection with he duodenum; however, it should be recalled that the first inch of duodenum has some degree of mobility. The position and the shape of the stomach are not fixed, since they vary considerably and are dependent upon the posture of the body, the amount of the gastric contents, the stage of gastric digestion, the degree of contraction of both abdominal and gastric musculature, the pressure of surrounding viscera, respiration and gastric tonus. The long axis of the viscus passes downward, forward, to the right and finally backward and slightly upward. Its shape has been likened to a “horn of plenty” as it lies in the upper left part of the abdomen. It is largely under shelter of the ribs, from which it is separated by the diaphragm; the lower part of the left pleura and the left lung overlap it. Therefore, it lies in the epigastric and the left hypochondriac regions in such a manner that only one sixth of this viscus is to the right of the midline. The stomach has 2 orifices, 2 curvatures, 2 surfaces and 2 incisurae. It is further subdivided into a fundus, a body and a pyloric portion. The 2 incisurae, or “notches,” are the incisura angularis and the incisura cardiaca (cardiac notch). The left border of the esophagus is not continuous with the greater curvature as a straight line but meets it at an acute angle and forms the cardiac notch (incisura cardiaca). The incisura angularis  (angular notch) is the deepest part of the concavity formed by the lesser curvature; therefore, it is the angle formed by the junction of the vertical and the horizontal parts of the lesser curvature; it is an important landmark in surgery of the stomach. If we locate the cardiac notch and draw a horizontal line across it and then drop an oblique line from the incisura angularis to the greater curvature, we shall have constructed the subdivisions of the stomach, namely: 1. The fundus is above the level of and to the left of the cardiac notch. 2. The body is that part which lies between the cardiac notch and the incisura angularis. 3. The pyloric portion, the remainder, is further subdivided into pyloric antrum and pyloric canal. The 2 orifices are the cardiac and the pyloric. The cardiac orifice (cardia) is the point of junction between the esophagus and the stomach; it marks that point at which the Stomach (Ventriculus or Gaster) 403 2 curvatures begin. The esophageal end, which has been referred to as the cardia, is fixed to the diaphragm. It is about I inch to the left of the midline, about 4 inches behind the 7th left costal cartilage and is located at the level of the 9th thoracic spine. It presents the following boundaries: in front, the left lobe of the liver; behind, the diaphragm; to its right, the esophageal branches of the left gastric vessels. The pyloric orifice is the communication between the stomach and the duodenum (duodenopyloric junction). This opening lies 1 inch to the right of the midline at the level of the 1st lumbar vertebra. The 2 surfaces are anterior and posterior. The anterior surface is more convex than the posterior and is directed upward and forward. It lies below the lesser curvature and is covered by the left and also by a part of the right lobe of the liver; therefore, in the epigastrium and below the xiphoid, the stomach is not in immediate contact with the anterior abdominal wall. Downward and to the left, however, there is a gastric triangle formed where this surface rests against the inner surface of the abdominal wall. It is bounded on the left by the 8th and the 9^th costal cartilages, on the right by the free margin of the liver and below by the transverse colon. It represents the most accessible portion of the stomach through an abdominal incision. In the left hypochondriac region, the stomach is covered not only by the ribs and the intercostal muscles but also by the left lung, the left pleural cavity and by the diaphragm. Thus, penetrating wounds in this region may injure the pleura, the lung and the stomach; therefore, gastric contents may escape into the pleural cavity. The so-called space of Traube is situated in the left hypochondriac region and represents that portion of the stomach which is not covered by the neighboring viscera. It is bounded above and to the right by the inferior margin of the left lung; below and to the right by the costal margin; and posteriorly and to the left by the spleen. When the stomach is empty, the transverse colon is displaced upward and comes to lie in front of the contracted viscus. The posterior surface runs downward and backward and forms a large part of the anterior wall of the lesser peritoneal sac (omental bursa). This sac separates the posterior surface from the so-called “stomach bed.” The greater curvature is in relation to the transverse colon below and behind; the adjoining part of the posterior surface rests on the transverse mesocolon. Above the transverse mesocolon, the stomach is in contact with the anterior surface of the pancreas; above the pancreas, the stomach lies to the left of the median plane and rests on the upper part of the left kidney and the left suprarenal gland. At a still higher level, the stomach (fundus) occupies the concave gastric area of the spleen and comes into relationship with the left half of the diaphragm. The normal stomach is separated anteriorly and posteriorly from the neighboring organs only by capillary spaces; this separation is effected in such a manner that direct contact is made. The 2 curvatures are the lesser on the right and the greater on the left. The lesser curvature extends between the cardiac and the pyloric orifices. It has vertical and horizontal parts which join at the incisura angularis and form a concave border in the form of a letter “J.” This curvature is continuous with the right margin of the esophagus and normally is overlapped by the liver. It affords attachment for the lesser omentum (gastrohepatic part) and contains the arterial circle formed by the right and the left gastric arteries. The greater curvature is convex and is 4 or 5 times as long as the lesser. Its upper third is directed toward the left; the middle third, downward and to the left; and the lower third, downward and to the right. It starts at the incisura cardiaca, passes upward as high as the 6th left costal cartilage and ends at the pylorus. Along the lower part of the greater curvature, the 2 layers of peritoneum which envelop the stomach pass downward as the greater omentum; on the left, they pass backward toward the spleen as the gastrosplenic ligament. Although the lesser curvature is comparatively fixed owing to its attachments, the greater curvature is freely movable, and its position alters as the stomach becomes full or empty, contracted or relaxed. When an individual is standing, the greater curvature may descend to the umbilicus or below it, but when lying down, it is an inch or more above the umbilicus. In ptosis, the curvatures become more nearly vertical in position, and both curvatures descend; but in gastric dilatation the greater curvature is lower, without altering the position of the somewhat fixed lesser curvature. The right and the left gastroepiploic vessels form an arterial circle as they separate the 2 layers of peritoneum which are attached here. The fundus is the rounded uppermost part of the stomach which is situated above the level of the esophageal junction; during life, it probably always contains gas. It bulges upward into the left cupola of the diaphragm as high as the level of the 5th costal cartilage and, therefore, is related to the heart, the pericardium and the left lung. This partly explains the increased cardiac activity and the accelerated respirations which are produced by the upward pressure of a full or distended stomach. The top of the fundus is almost on a level with the left male nipple. The body of the stomach is the main portion which lies between the incisura angularis and the incisura cardiaca (between the fundus and the pylorus). Its general direction is oblique and to the left. The pylorus is the point of junction between the stomach and the duodenum. The outer surface of the pylorus is marked by a circular constriction (duodenopyloric constriction). It lies in the transpylo ric plane, about 1 inch to the right of the midline, behind the quadrate lobe of the liver and in front of the neck of the pancreas. Its position usually is marked by a prepyloric vein (vein of Mayo) which descends over its anterior surface from the right gastric vein to the right gastroepiploic vein. However, this vein may be ill-defined. The pyloric portion of the stomach is divided into proximal and distal parts. The proximal part represents a slight dilatation and is known as the pyloric antrum. The distal part is more tubular and is called the pyloric canal. The pylorus usually is considered as that terminal half-inch of stomach which is in contact with and covered by the liver. Since the liver hides it from view and since most perforated peptic ulcers occur in this area, it becomes an area of great surgical importance. The pylorus has thicker walls than the rest of the stomach because of an increase in the circular muscle fibers. This thick muscular ring closes and relaxes the pyloric orifice and forms the pyloric sphincter. Normally, the pylorus is in a closed state, but when open it is capable of admitting a fingertip. Despite its narrowness, many cases are reported in which foreign bodies as large as pencils, forks, keys, etc. have been passed through it. Behind, it is related to the portal vein, the hepatic artery and the common duct. Two layers of peritoneum envelop the stomach; at the lesser curvature these meet and pass upward as the lesser omentum, which becomes attached to the liver and the diaphragm. This omentum has 2 parts: the gastrohepatic and the duodenohepatic. The gastrohepatic part is avascular, thin, transparent and contains no important structures. The duodenohepatic part of the lesser omentum is thick and contains 3 vital structures: the common duct, the portal vein and the hepatic artery. The 2 layers of peritoneum which clothe the stomach meet at the greater curvature and pass downward as one great fold. Different parts of this fold receive different names according to their attachments: the gastrohepatic ligament is attached to the diaphragm; the gastrosplenic ligament, to the spleen; and the greater omentum, to the transverse colon. That portion of greater omentum which is situated between the stomach and the transverse colon is known as the gastrocolic ligament.

The arterial supply to the stomach is derived from the celiac axis. The lesser curvature is supplied by the left gastric (coronary) artery which reaches the cardiac end of the curvature along the left edge of the gastrohepatic omentum. It passes upward and to the left on the left eras of the diaphragm, and then it turns over the upper border of the lesser sac to reach the stomach. It continues downward, forward and to the right, and passes along the curvature to anastomose with the right gastric (pyloric) artery, a branch of the hepatic. The greater curvature is supplied by the following arteries: The vasa brevia (short gastric), which are usually 4 or 5 in number arise from the splenic artery or from one of its terminal branches. These pass between the layers of the gastrosplenic ligament to the left end of the greater curvature and anastomose with esophageal, gastric branches, and the left gastroepiploic artery. The left gastroepiploic artery arises from the splenic near its termination, passes in the gastrosplenic ligament to the stomach and then runs from left to right along the greater curvature between the layers of the gastrocolic ligament. It anastomoses with the right gastroepiploic artery after sending branches to both surfaces of the stomach. The gastroduodenal artery takes origin from the hepatic above the duodenum, passes behind it between the neck of the pancreas and the duodenum and ends at the lower border of the first part of the duodenum by dividing into a superior pancreaticoduodenal and a right gastroepiploic. The latter artery passes from right to left between the layers of the gastroepiploic omentum, sending gastric branches upward to both walls of the stomach, and ends by anastomosing with the left gastroepiploic

The veins of the stomach correspond to the arteries; they terminate in the portal vein or the 2 large vessels which form it (superior mesenteric and splenic veins). They form 2 great loops: the one along the lesser curvature and the other along the greater. Associated with these are some short gastric veins at the fundus. The loop on the lesser curvature is made up of the left gastric (coronary) and the right gastric veins. The left gastric vein accompanies the left gastric artery along the lesser curvature and receives tributaries from both surfaces of that organ and also from the esophagus. It continues backward in the left gastropancreatic fold to the posterior wall of the abdomen; then it turns downward and to the right and empties into the portal vein. The right gastric vein passes to the right along the lesser curvature of the stomach and at the pylorus turns backward and enters the portal vein. It receives venous blood from both surfaces of the stomach and from a vein which travels upward in front of the pylorus, the prepyloric vein of Mayo. The latter vessel usually connects the right gastric and the gastroepiploic veins. The venous loop along the greater curvature lies between the layers of the greater omentum and is made up of the left and the right gastroepiploic veins. The left gastroepiploic vein passes upward and to the left and empties into the splenic vein. The right gastroepiploic vein runs to the right, arches backward at the pylorus and usually enters the superior mesenteric. The left gastric vein (portal system) anastomoses with the lower esophageal vein; the latter in turn anastomoses with the upper esophageal veins which drain through the azygos into the caval venous system. On this way, an important communication is formed between the portal and the caval systems (portacaval anastomosis). The veins at the inferior end of the esophagus may become distended and varicosed in such conditions as cirrhosis of the liver (portal obstruction); their rupture results in severe hematemesis which may be fatal.

The lymph drainage of the stomach follows the 3 branches of the celiac axis (hepatic, gastric and splenic). Hence,there are 3 sets of lymph glands and ducts: (1) hepatic, (2) gastric and (3) pancreaticosplenic

Nerves. The stomach is innervated by both the parasympathetic and the sympathetic nervous systems . The parasympathetic nerve supply is derived from the vagus nerves which originate in the medulla, descend in the carotid sheath and into the thorax. Esophagogastrointestinal Tract the formation of the so-called posterior pulmonary plexus, and from these, branches continue to the esophagus and the stomach. The nerves then pass through the esophageal orifice of the diaphragm and reach the respective surfaces of the stomach, where the right vagus is known as the posterior gastric nerve and the left vagus as the anterior; they pass along the lesser curvature of the stomach. The left vagus nerve sends branches to the liver and to the anterior wall of the stomach. Those branches traveling to the liver turn to the right, pass through the lesser omentum and to the porta hepatis. The gastric  branches divide into several smaller nerves which spread over the anterior wall and can be followed to the greater curvature. The right vagus nerve is arranged in a similar manner: one part goes to the celiac plexus and the remainder supplies the posterior wall of the stomach. The sympathetic nerve supply to the stomach is derived from the celiac (solar) plexus. This consists of a network of intercommunicating nerve fibers and 2 relatively large flat. ganglia, the celiac ganglia The plexus lies in front of the upper part of the abdominal portion of the aorta around the celiac artery. The right and the left celiac ganglia lie on corresponding crura of the diaphragm, the right being situated behind the inferior vena cava. The fibers to the plexus reach it from the greater and the lesser splanchnic nerves. The greater splanchnic nerve on either side arises from the right sympathetic chain between the 5th and the 10th thoracic ganglia.The lesser splanchnic nerve also arises from the sympathetic chain in the region of the 9th and the 10th thoracic ganglia. The greater splanchnic nerve usually terminates in the upper end of the ganglion; the lesser splanchnic reaches the lower end. The celiac plexus supplies nerves which travel along the branches of the celiac artery; these fibers continue along the subdivisions of the 3 vessels and terminate in the stomach wall. In the gastric wall, a plexus is situated between the muscle layers (myenteric plexus) and another in the submucosa (submucous plexus).

SURGICAL CONSIDERATIONS

GASTROJEJUNOSTOMY Gastrojejunostomy is indicated in the patient who has a pyloric obstruction and low gastric acidity. It is used also as a palliative measure to provide relief for an obstructed pylorus (inoperable carcinoma) or as a preliminary procedure for future surgery. The operation may be done anterior or posterior to the transverse colon. A posterior gastrojejunostomy is accomplished by passing the posterior wall of the stomach through a rent in the transverse mesocolon and performing an anastomosis between the stomach and a proximal loop of jejunum. The gastric site for the stoma should be placed at the most available and dependent part near the greater curvature and in line with the esophagus. The details and the structural orientation may be found in the description of gastric resection which follows. Following the anastomosis, the rent  in the transverse mesocolon is sutured to the posterior wall of the stomach to prevent internal herniation. Anterior gastrojejunostomy is preferred by many surgeons; it is technically simpler, does not endanger the middle colic artery and does away with many of the hazards if reoperation becomes necessary. The anastomosis is placed on the anterior surface of the stomach and anterior to the transverse colon. In an anterior gastrojejunostomy it is preferable to suture the greater curvature to the proximal end of the jejunum.

TRANSABDOMINAL VAGUS NERVE SECTION (VAGOTOMY).

The abdominal approach to the gastric nerves (vagi) allows exploration of the abdominal contents and the lesion; it also facilitates the performance of a gastro-enterostomy if pyloric obstruction is present or is likely to occur. A long incision is necessary for proper exposure. A left muscle-splitting rectus incision which commences in the angle between the xiphoid and the left costal cartilage and extends 1 or 2 inches below the umbilicus is utilized. The peritoneal cavity is entered, and the left triangular ligament of the liver is exposed. This bloodless fold is severed, and it then becomes possible to retract the left lobe of the liver to the right. The peritoneum covering the lower end of the esophagus is incised, the posterior mediastinum is entered, and the lower 3 or 4 inches of the esophagus are mobilized and exposed. The vagus nerves are identified by palpation; they feel like taut cords which can be differentiated readily from the more yielding muscle of the esophagus. The left (anterior) vagus has a tendency to hug the esophagus, but the right (posterior) vagus travels a slight distance away from it. By finger dissection the fibers are assembled into 2 main trunks comprising the right and the left vagi; these are ligated and divided. The position of the right and the left trunks below the esophageal hiatus is found to remarkably constant. At the conclusion of operation, the left lobe of the liver is permitted to fall into place, it has been found unnecessary to resuture the severed left triangular ligament.

Liver

The liver is the largest gland in the body; it is extremely vascular and has many functions to perform. It receives its arterial blood supply from the hepatic artery, and the portal vein conveys blood to it from the intestinal tract. The blood of the liver is drained by the hepatic veins, which open into the inferior vena cava. This organ resembles the shape of a pyramid, the base being to the fight and the apex to the left; the sides of the pyramid are formed by the superior, the inferior, the anterior and the posterior surfaces. In the adult it constitutes approximately l/50th of the body weight; it occupies the uppermost part of the abdomen, chiefly on the right side. The organ is in close relation with the diaphragm and is covered by the ribs, which afford it some protection. At birth the liver is relatively larger. This is especially true of the left lobe; the prominent bulging of an infant’s abdomen is mainly due to the large size of the gland. The falciform ligament of the liver is a wide fold of peritoneum which lies obliquely between the liver and the anterior abdominal wall. The right surface of this ligament is in close contact with the abdominal wall, and the left surface is in contact with the liver. The ligament has 3 borders: an upper border which is attached to the diaphragm and to the anterior abdominal wall as far as the umbilicus; the second border is attached to the upper and the anterior surfaces of the liver, dividing it into right and left lobes; the third border is a free edge where the 2 layers of the ligament become continuous with each other. The round ligament (ligamentum teres) passes in this free edge. If the left lobe of the liver is pulled away from the diaphragm, a fold of peritoneum the left triangular ligament, is placed on the stretch. It connects the left hepatic lobe to the diaphragm and presents 3 borders. One border is attached to the back of the upper surface of the left lobe; the second is attached to the central tendon of the diaphragm and the third is a free edge which is directed toward the left where the 2 layers of the ligament are continuous with each other. If the fingers of the right hand are passed backward over the top of the right lobe, they are stopped by a layer of peritoneum which is known as the upper layer of the triangular {coronary) ligament. This is reflected from the back of the right lobe onto the diaphragm. If the fingers of the left hand are passed upward behind the right part of the right lobe and pressed backward, they will be stopped by the lower layer of the triangular {coronary) ligament. The lower layer is reflected from the inferior surface of the liver onto the right kidney, the adrenal gland and the inferior vena cava; it also is referred to as the hepatorenal ligament. Below this ligament is a peritoneal space known as the hepatorenal pouch (Morison’s). The upper and the lower layers of the coronary ligament approximate each other at the right extremity of the liver, and where they fuse they form the right triangular ligament. This ligament is not as well marked as the left, because its 2 layers diverge so rapidly. Between the 2 layers of the coronary ligament there is a fairly large triangular area of liver which is devoid of peritoneum and is known as the bare area; it is attached directly to the diaphragm by areolar tissue. The apex of this bare triangular area corresponds to the meeting point of the 2 layers of the coronary ligament on the right where they form the right triangular ligament. The base of the triangle is formed by the fossa for the inferior vena cava. The bare area is in contact with the inferior vena cava, the upper part of the right suprarenal gland and the diaphragm. It is connected to the liver by connective tissue in which are found the veins of Retzius, which form a portasystemic anastomosis. The student’s “crutch,” the time-honored letter “H,” is formed by structures which lie on the inferior surface of the liver. The left limb of the letter “H” divides this surface into right and left lobes. It contains embryonic structures, namely, the fissure for the ligamentum teres (left umbilical vein) in front and the fissure for the ductus venosus behind. Fetal blood is returned from the placenta to the fetus by means of the umbilical vein, which enters the abdomen at the umbilicus, passes upward along the free margin of the falciform ligament to the undersurface of the liver. At the transverse fissure of the liver (porta hepatis) it divides into 2 branches; one of these joins the portal vein and enters the right lobe, the other joins the ductus venosus, thereby shortcircuiting the blood to-the inferior vena cava. Therefore, since the umbilical vein and the ductus venosus were continuous with each other in fetal life, it is quite natural that their adult landmarks (ligamentum teres and ligamentum venosum) should also be continuous, thereby forming the left limb of the “H.” The right limb of the “H” contains visceral structures, the fossa for the gallbladder in front and the inferior vena cava behind. The transverse part of the “H” is formed by the porta hepatis (the transverse fissure) and this contains, from before backward, the hepatic duct, the hepatic artery and branches of the portal vein. The porta is deep and wide and is about 2 inches long; a portion of the lesser omentum is attached to it. The nerves of the liver and most of its lymph vessels also are found here. Besides these structures it also contains fatty tissue and some lymph glands which, when enlarged, may obstruct the flow of bile in the hepatic ducts, thereby causing jaundice. The hepatic duct is formed on the right side of the porta by the union of the right and the left hepatic ducts. The branches of the hepatic artery enter on the left side of the common duct and then pass behind the right and the left ducts; the portal vein lies behind the artery. The porta hepatis is bounded anteriorly by the quadrate lobe and posteriorly by the caudate lobe of the liver.

Surfaces. The base of the pyramidalshaped liver is the right lateral surface; it is somewhat quadrilateral and convex. It is related to the diaphragm opposite the 7th to the 11th ribs in the midaxillary line. The pleura and the right lung are important relations to this surface; they are separated by the diaphragm. In the midaxillary line the pleura overlaps the liver as low as the 10^th rib and the lung to the 8th. The 12th rib, asa rule, does not reach sufficiently far forward to come into relationship to this hepatic surface. Therefore, a puncture wound over the lower part of the right side of the thorax may pass through the pleura, the lung, the diaphragm, the peritoneum and the liver. The anterior surface of the liver is of considerable clinical importance, since it is the surface which is most readily accessible for examination as far as the 10th costal cartilage on the right side. The median portion, which lies against the anterior abdominal wall, is palpated easily and thus yields valuable information. If inspiration is forced, almost the entire inferior border of the liver can be felt. The superior surface is related to the diaphragm, which separates it from the 2 pleural sacs and the pericardium. On the right side it rises into a convexity that reaches almost to the level of the right nipple. On the left, the surface ends as a thin edge which is opposite the 5th rib in a line dropped from the left nipple. The posterior surface cannot be seen until the liver has been removed from the body On the left this surface is covered with peritoneum of the greater sac, and a groove made by the esophagus is formed here. In the median plane is the caudate lobe, which is covered with peritoneum of the lesser sac. This lobe lies between the fossa for the vena cava and the fossa for the ductus venosus. To the right of this the bare area is found. The inferior vena cava occupies the leftmost portion of the area, and the kidney and the adrenal gland encroach upon it from below. The inferior surface also has been called the visceral surface of the liver. It faces downward, to the left and backward. It is covered with the peritoneum of the greater sac and everywhere shows the imprints of viscera with which it is in contact. It is only distinctly separated from the inferior surface, and the “H” which has been described occupies this surface. The part of this surface which belongs to the left lobe isrelated to the stomach and to the lesser omentum. The gastric impression appears as a wide, shallow, concave area to the left. The omental part is a bulging prominence to the right and behind; it is called the tuber omentale. The quadrate lobe lies between the fissure for the ligamentum teres and the fossa for the gallbladder. This lobe is related to the pyloric part of the stomach and the first part of the duodenum below, and to the right part of the lesser omentum above. It is the quadrate lobe which attempts to seal over perforated peptic ulcers, the vast majority of which occur in this portion of the stomach or in the duodenum. The gallbladder lies in front of the first and the second parts of the duodenum, but the latter extends beyond it and is in relation to the adjoining part of the right lobe. Directly to the right of the duodenal area the right colic flexure leaves its imprint, and behind this the undersurface of the right lobe is related to the right kidney, which leaves its renal impression. The liver is completely covered with peritoneum except in 3 locations, namely, the bare area, the groove for the inferior vena cava and the gallbladder fossa. The lesser omentum is attached to the margins of the porta hepatis and around its right extremity; its 2 layers are continued from the left extremity of the porta hepatis to the fissure for the ligamentum venosum. At the upper end of this fissure these 2 layers separate. The ligaments mentioned in connection with the liver should not be regarded as supporting the entire weight of the organ, since it, like other abdominal and pelvic organs, is kept in place by intra-abdominal pressure which is attributed mainly to the tonus of the muscles of the anterior and the lateral abdominal walls. Therefore, it is of little or no consequence when one of the so-called “supporting” ligaments of the liver is severed during surgical procedures, since the liver will not become ptotic

The liver has 3 vessels associated with it: the hepatic artery, the portal vein and the hepatic veins. The hepatic artery, one of the trifurcating branches of the celiac axis, supplies arterial blood to the substance of the liver.

The hepatic artery varied in the origin, the caliber, number and the distribution of its main branches. The typical common hepatic artery divides into a right, a middle (to the quadrate lobe) and a left branch.To shut off completely the arterial blood supply to the liver would be fatal, but a collateral anastomosis exists. In recent years opinions have been divided as to whether or not necrosis will result in man from ligation of a common, a right or a left hepatic artery. Viability of the liver may be explained by the following: (1) If the common hepatic artery is ligated, hepatic circulation is maintained in a ratio of 1 to 8 because the right artery may arise from the superior mesenteric artery. (2) If the right or the left hepatic artery is ligated, the corresponding lobe does not of necessity necrose. This is explained by the fact that the larger branches of the right and the left hepatic arteries (precapillaries) anastomose with each other in the fissure of the liver. (3) If the hepatic artery is obstructed gradually on the aortic side of the right gastric artery, circulation may be maintained by the anastomosis of the right and the left gastric arteries. Hence, it must be accepted that the effects of ligation of the so-called “normal” hepatic artery would differ at various levels

Veins. The portal vein also brings a great quantity of blood to the liver. This vessel is formed between the head and the neck of the pancreas by the union of the splenic, the superior mesenteric and the inferior mesenteric veins. It forms a rather thick vessel, which measures about 7 1/2 cm. in length. At the porta hepatis it divides into right and left branches. If the portal vein is obstructed by either intrahepatic or extrahepatic causes, the portal blood is shunted to the systemic veins where the 2 systems meet. This collateral circulation has been referred to as the accessory portal system. The hepatic veins carry blood from the liver to the inferior vena cava. Some of these veins are small and open into the vena cava at various points; however, the chief hepatic veins are a left and a right, coming respectively from the right and the left liver lobes. They enter the inferior vena cava immediately before it leaves the liver.

Nerves. The nerves of the liver are derived from the left vagus and the sympathetic. They enter at the porta hepatis and accompany the vessels and the ducts to the interlobular spaces.

Lymphatics. The lymph vessels of the liver terminate largely in a small group of lymph glands in and around the porta hepatis. The efferent vessels from these glands pass to the celiac lymph glands. Some of the superficial lymph vessels in the anterior surface of the liver pass to the diaphragm in the falciform ligament and finally reach the mediastinal glands. There is another group which accompanies the inferior vena cava into the thorax and ends in a few small glands which are related to the intrathoracic part of the vessel

LIVER RESECTION Resective lesions have increased during recent years, particularly neoplastic and traumatic lesions of the liver. Major hepatic resections with lowered morbidity and mortality are being accomplished by strict adherence to surgical principles and anatomic knowledge. The works of Healey and Schroy and of Goldsmith and Woodburne can be referred to for their views regarding “planes” of resection. The caudate lobe is usually treated as an area unto itself. The Longmire operation (intrahepatic cholangiojejunostomy) and its modifications should be in the armamentarium of every surgeon interested in biliary tract surgery. This may be a last resort  whereby a life can be saved following injury to and reparative processes of the common duct.