RADIOLOGICAL EXAMINATION OF THE LUNGS AND PLEURA

RADIOLOGICAL EXAMINATION OF THE LUNGS AND PLEURA.

 

The imaging investigations ot the chest may be considered under the following headings:

1.    Simple X-ray

2.    Chest screening

3.    Tomography

4.    Bronchography

5.    Pulmonary angiography

6.    Isotope scanning

7.    Computed tomography

8.    MRI

9.    Needle biopsy.

Simple X-ray

In hospital practice many patients have a routine chest X-ray on admission. This is done not only to exclude serious chest disease, but also to provide evidence of the preoperative condition of the chest in patients about to undergo surgery. Postoperative chest complications include basal collapse, lung infections, and pulmonary embolus. In the assessment of such postoperative complications it is important to have a preoperative film for comparison. Chest X-ray also shows the size and shape of the heart and provides base line evidence of the cardiac status.

Simple radiography of the chest is also carried out as a routine in all patients with suspected chest disease. The study of chest X-rays requires an intimate knowledge of the normal anatomy of the lungs including the bronchi and their lobar and segmental arrangements. Lesions must be anatomically localised and this will often require a lateral projection as well as a simple posteroanterior film. In studying the simple X-ray the radiologist will note not only the lung fields but also the heart and mediastinum, the pulmonary vasculature, the position of the diaphragm, and the condition of the bony thorax.

                                 

                  

Fig. 2.1 Diagram illustrating the anatomy of the main bronchi and segmental divisions. Nomenclature approved by the Thoracic Society. (Reproduced by permission of the Editors of Thorax.)

                            Upper Lobe

1. Apical bronchus 2. Posterior bronchus 3. Anterior bronchus

Middle Lobe               Lingula

4.   Lateral bronchus                         4.   Superior bronchus

5.   Medial bronchus                         5.    Inferior bronchus

Lower Lobe

6.       Apical bronchus                         6.    Apical bronchus

7.   Medial basal (cardiac)                 8.    Anterior basal bronchus

6.   Anterior basal bronchus              9.    Lateral basal bronchus

9. Lateral basal bronchus                10.    Posterior basal bronchus

10. Posterior basal bronchus

PLAIN   FILMS

The standard view used is the posteroanterior (PA) projection; others are listed below.

•  Anteroposterior (AP): used for ill patients.

•  Lateral: localizes an abnormality seen on PA view.

•  Supine: valuable in infants and ill patients.

•  Oblique: useful to demonstrate pleural, chest wall and rib abnormalities.

•  Erect: detects gas under the diaphragm.

•  Expiratory: a pneumothorax becomes more prominent.

•  Lateral decubitus: small pleural effusions or subpulmonary effusions are recognized more easily with the affected side dependent.

COMPUTED  TOMOGRAPHY  (CT)

•  Excellent detail for staging mediastinal and bronchial neoplasms.

•  Valuable in detection of diffuse pulmonary disease.

•  Earlier identification of pleural plaques in asbestos exposure.

•  Diagnosis of aneurysm or dissection.

•  Elucidating the nature of a lung opacity.

•  As an aid to lung biopsy.

MAGNETIC  RESONANCE   IMAGING  (MRI)

The principal indications are evaluation of mediastinal masses, aortic dis­section and staging bronchial carcinoma, if vascular invasion is suspected.

 

ULTRASOUND

Ultrasound examination of the chest determines the presence of pleural effusions and loculated fluid. It will accurately locate small quantities of fluid for aspiration. Biopsy of pleural lesions may be carried out using ultrasound guidance.

LUNG  BIOPSY

A needle is inserted directly into the mass to be biopsied, obtaining tissue samples. Biopsy should not be carried out if there is a suspicion of an arteriovenous malformation or hydatid cyst. Poor respiratory function is also a contraindication, as a pneumothorax following biopsy may seriously compromise the patient.

PULMONARY  ANGIOGRAPHY

The pulmonary artery is selectively catheterized and contrast injected to visualize the pulmonary arterial and venous circulation.

ISOTOPES

Combined perfusion scanning with technetium-99m-labelled macroaggre-gates of human albumin and ventilation scanning with inhaled radioactive gas or aerosol typically produces a perfusion defect and not a ventilation defect in pulmonary embolus.

 

Fig. Normal ventilation (V) and perfusion (Q) scan.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 Fig. Normal pulmonary angiogram

 

Fig. Lung biopsy under CT control. The needle (arrow) has been inserted through the posterior chest wall.

Inspecting a chest X-ray

The student inspecting a chest film should try to examine it in a systematic manner. Though a radiologist may give an opinion, after what appears to the student only a cursory inspection, this is based on years of experience, and the examination of many thousands of films. The radiologist will have noted the normality or abnormality of all the following features:

1.    The lung fields and pulmonary vessels

2.    The heart and mediastinum

3.    The diaphragm and subdiaphragmatic areas

4.    The bony thorax (ribs, clavicles, scapulae, spine and shoulder joints)

5.    The soft tissues (muscles, breast and cutaneous tissues).

The student should train himself to follow a routine which examines each of the above features in turn. In order to examine the lung fields and pulmonary vessels fully, it is helpful to divide each side of the chest into three zones – upper, middle and lower – and to check each in turoting any deviation from the normal or dif­ference from the other side. A similar systematic approach should be applied to the other features listed above, since significant abnormalities may be seen in any of them.

Thus an irregular bony defect in a rib with an adjacent soft tissue swelling may represent the first evidence of metastasis. An elevated diaphragm on one side with a small basal effusion may be evidence of a subphrenic abscess. A small bulge of the upper mediastinum may represent a tumour or an aneurysm. These few examples serve to illustrate the importance of the simple chest film in identifying disease not only of the lung parenchyma but also of many other systems.

Chest screening

In the early days of radiology chest screening was regarded as an essential part of the examination of the chest. Chest screening, however, involves an increased dose of irradiation to the patient compared with a simple chest X-ray. In practice it is now only carried out for the elucidation of specific problems. Thus it may be used to determine whether the diaphragm is moving normally or is paralysed; to assess the relationship of an opacity to other structures more ac­curately by observing it with different degrees of rotation on the screen; or to confirm valvar or other intracardiac calcification since this is much better visualised by screening with an image intensifier than on a simple film.

Tomography

This is used for the clearer demonstration of doubtful opacities in the lung field for the better visualisation of masses or apparent masses at the lung hila; for the study of the margins of opacities in the lung – whether clear-cut or infiltrating surrounding lung; and for the better demonstration of cavities or suspected cavities within a lung lesion, or of calcification in an opacity.

Fig. Tomogram of basal pulmonary opacity confirms that it is due to an angioma. Note the tortuous dilated vein (arrow).

Bronchography

This procedure was once widely used, mainly for the demonstration of bronchiectasis. It was also sometimes used for the demonstration of an obstructed or stenosed bronchus in suspected carcinoma. Bronchography was performed in the X-ray department by the radiologist. There were several techniques available.

The contrast medium, propyliodine (Dionosil), was injected over the back of the tongue, or through the nares, or directly through the cricothyroid membrane. In all cases the trachea is first rendered anaesthetic by means of local anaesthesia. Once the contrast medium had been injected the patient was tilted into the various positions necessary for filling the appropriate lobes of the lung with contrast.

High resolution CT (HRCT) has now replaced broncography in the assessment of bronchiectasis.

Fig. Bronchogram showing good filling of the left bronchial tree. There is bronchiectasis involving the left lower lobe and part of the lingula.

Pulmonary angiography

Pulmonary angiography is performed by passing a catheter from a peripheral vein through the right atrium and right ventricle into the main pulmonary artery and then if necessary into the right or left pulmonary artery. Contrast medium is injected so as to opacify the blood supply of the area under examination. The main use of the method is to confirm a suspected diagnosis of pulmonary embolus.

Pulmonary angiography is also occasionally used for the elucidation of opacities in the lung fields; e.g., to confirm a diagnosis of arteriovenous fistula or angiomatous malformation in the lung. Most of these cases, however, can be diagnosed by simple X-ray or tomography or by CT.

Radioisotope scanning

Radioisotope scanning of the lungs is widely practised to confirm or refute a clinical diagnosis or suspicion of pulmonary embolus. If the findings are normal the more invasive pulmonary angiography can be dispensed with, and if they are abnormal and typical, treatment may be instituted.

Lung scans can be performed following intravenous injection of technetium (“Tc^m)-labelled macroaggregates or microspheres. This is known as the perfusion or P scan. It can also be performed by inhalation of radioactive xenon (¹³³Xe) or krypton (⁸¹Kr^m). This is known as the ventilation or Q scan.

If the perfusion scan is normal no further action is required, but if it shows perfusion defects suggestive of embolism then a ventilation scan can be done. Typically in pulmonary embolus the lung remains aerated and the ventilation scan remains normal, giving rise to the so called ‘mismatching’ of the P and Q scans. This mismatch is virtually diagnostic of pulmonary emboli.

NORMAL CHEST

Some pertinent radiological considerations

Hilar shadows. Predominantly due to pulmonary arteries: the left hilum is smaller and a little higher than the right.

Horizontal fissure. A white ‘hair-line’ shadow dividing the right upper and middle lobes and extending up to the right hilum: it is not always seen.

Cardiac shadow. The right atrium is seen just to the right of the thoracic spine. The inferior border is formed by the right ventricle and the left border by the left ventricle.

Diaphragm. The right leaf is usually higher than the left, though occasion­ally the converse may be true.

Trachea. Lies in the midline with bifurcation at the level of T6. It deviates slightly to the right at the level of the aortic knuckle.

Lung fields. The intrapulmonary arteries radiate from the pulmonary hila and taper towards the periphery contributing to the majority of the lung markings, with a smaller component from the pulmonary veins. The right lung is divided into three lobes: the upper, a small middle lobe and lower lobe. The left lung has two lobes, the upper (including the lingula) and lower.

VIEWING  A   CHEST  FILM

Inspect the film for adequate penetration (lower thoracic spine just visible), inspiration (diaphragms at level of fifth or sixth ribs anteriorly) and rotation (the spinous processes of the upper thoracic vertebrae lie midway between the medial ends of the clavicles).

Examine the chest X-ray systematically to ensure that all areas are covered; skeletal and soft tissues are best left to the end. Keep to a routine but with practice it will be possible to spot the abnormalities and describe them first: lungs; hilar shadows; cardiac shadow; mediastinum; diaphragms; skeletal and soft tissues.

Lungs. Scan both lungs, starting at the apices and working downwards. Compare the appearances of each zone with the other side. (The lungs can be divided approximately into three zones: the upper, middle and lower zones.) The only shadows normally visible, apart from the fissures, should be vascular in origin, so concentrate on searching for any areas of homogeneous shadowing or a mass lesion. It may be easier to describe an opacity within a zone and later determine the lung lobe.

Hilar shadows. A common site for lymphadenopathy and bronchial carci­noma: look for increased density and irregularity as well as enlargement of the hilar shadow.

Cardiac shadow. Note the size and shape. Specific chamber enlargement is often difficult to identify: pay attention to and comment on the overall size of the heart.

Mediastinum. Assess for mass lesions and also for mediastinal shift by position of the trachea and cardiac shadow.

Diaphragms. The costophrenic angles should be clear, sharp and deep. Blunting may indicate a pleural effusion or old pleural thickening. The upper surfaces should be clearly defined: poor definition often implies basal lung pathology. Flattening of the diaphragms suggests hyperinflation and chronic obstructive airways disease.

Skeletal and soft tissues. Look at the periphery of the film; ribs for fractures or secondary deposits; appearances of the breast shadows and whether there has been a mastectomy; under diaphragms; shoulders etc.

NORMAL  APPEARANCES

The lungs appear translucent with only branches of the pulmonary arteries and veins visible.There is no other shadowing.

Fig. Normal lung fields.

RETICULAR/INTERSTITIAL  SHADOWING

This is produced by thickening of the tissues around the alveoli, the lung interstitium, and visualized as a fine or coarse branching linear pattern. Typical conditions giving rise to this type of shadowing are lung fibrosis and pneumoconiosis.

Fig. Interstitial lung shadowing.

NODULAR  SHADOWING

Nodular shadowing is due to small discrete spherical opacities I-5 mm in diameter. Causes include: miliary tuberculosis; pneumoconiosis; sarcoido­sis; neoplastic: miliary carcinomatosis from thyroid, melanoma, etc.

Fig. 2.7 Nodular shadowing.

CONSOLIDATION

Consolidation is due to replacement of air in the alveoli by fluid or occasionally tissue, resulting in areas of confluent homogeneous shadowing. Patent bronchi and some small airways are often still visible as linear lucen-cies, when surrounded by fluid-filled alveoli: this sign is called an air bronchogram.

 

 

Fig. Consolidation showing an air bronchogram.

BRONCHIAL CARCINOMA: PERIPHERAL

This is a common primary tumour, with approximately half found in the peripheral lung fields.The main histological types are squamous, small (oat) cell, anaplastic, adenocarcinoma and the rarer alveolar cell carcinoma.

PRESENTATION

Haemoptysis; respiratory symptoms such as cough and shortness of breath; weight loss; cerebral or lymph-node metastases; slowly resolving pneumonia; routine chest; paraneoplastic syndromes such as inappropriate antidiuretic hormone (ADH) secretion.

RADIOLOGICAL FEATURES

Bronchoscopy may be negative in peripheral lesions, as visualization is not possible distal to the segmental bronchi. The following features may be present on a plain chest film.

•  Lobulated or spiculated mass but sometimes with a smooth outline.

•  Associated hilar gland enlargement, pleural effusion, areas of collapse or consolidation.

•  Cavitation found in 15% with central air lucency, an air/fluid level and a wall of variable thickness. Squamous carcinomas frequently cavitate.

•  Tumours at the lung apex (Pancoast’s tumour) can invade the brachial plexus, resulting in shoulder and arm pain with wasting of the hand, or invasion of the sympathetic chain may give rise to Horner’s syndrome.

Further investigations include:

•  CTIMRI chest and upper abdomen. Assesses spread and determines operability. This examination will establish whether there has been any metastatic spread into the mediastinal lymph nodes, chest wall, liver or adrenals. MRI is generally more accurate in defining mediastinal and vascular invasion.

•  Lung biopsy. Either under fluoroscopy or CT control to obtain a sample for histology.

DIFFERENTIAL  DIAGNOSIS  OF  SOLITARY  LUNG  MASS

•  Metastasis: sometimes single, most commonly from breast, kidney, colon and testicular tumours.

•  Tuberculoma: often apical and may have areas of calcification.

Benign neoplasms: bronchial adenoma (usually perihilar), hamartoma (most common benign tumour of the lung), rarely focal areas of pneumonia, hydatid cyst, haematoma or arteriovenous malformation.

Fig.  Bronchial carcinoma: solitary circular opacity in the right mid-zone (‘coin lesion’).

Fig. Pancoast’s tumour: mass at the right apex with rib destruction.

Central bronchial carcinoma arises from the major bronchi, causing a mass in the hilar region.

BRONCHIAL CARCINOMA:CENTRAL

PRESENTATION: As in peripheral carcinoma.

RADIOLOGICAL  FEATURES

On a chest X-ray, the central mass causes the hilar shadow to enlarge, assume an increased density or an irregular outline. As the tumour increases in size, narrowing of the bronchial lumen may cause collapse of the distal lung and consolidation due to secondary infection. A large tumour often gives rise to complete collapse of a lung and may result in opacification of the entire hemithorax.

CT/MRI aids identification of extent and spread of the tumour to:

•  lymph nodes: mediastinal and hilar lymphadenopathy;

•  oesophagus: direct invasion with dysphagia or fistula;

•  pleura: pleural effusion;

•  pericardium: pericardial effusion;

•  bone: direct extension into sternum or ribs;

•  superior vena cava: obstruction with venous engorgement. Common sites of distant metastases are:

•  brain;

•  bone;

•  adrenals;

•  liver.

Lymphangitis carcinomatosa: dissemination of carcinoma through lym­phatic channels of the lung, usually unilateral, but may be bilateral.

Invasion of the tumour may also involve the phrenic nerve (elevation of the diaphragm) or laryngeal nerve (hoarseness).

TREATMENT

•  Surgical resection: inoperable if direct invasion or distant metastases.

•  Chemotherapy: especially for oat cell carcinoma.

•  Radiotherapy: inoperable tumours or when complications arise:

brain metastases;

spinal cord compression;

superior vena cava obstruction.

Fig.  Central bronchial carcinoma: large left hilar mass.

 

Fig. CT scan demonstrating the left hilar mass (arrow). There is no associated lymphadenopathy but a left pleural effusion is present.

 

PULMONARY METASTASES

Metastatic disease to the lungs and rib cage is a common complication of primary neoplastic disease originating elsewhere, usually through the haematogenous route. Tumours of the breast, renal tract, testis, gastrointestinal tract, thyroid and bone are often the primary source.

RADIOLOGICAL  FEATURES

Abnormalities can be seen on either plain films or CT. Metastatic disease to the chest may involve one or more of the following: lungs; pleura; lymph nodes; local invasion; bony skeleton.

Lungs

Virtually any malignancy may give secondary deposits in the lungs. Deposits usually appear as well-defined, multiple, round opacities of differing sizes in the lung fields. CT is particularly sensitive in detecting metastases not visible on a chest X-ray and helpful in monitoring response to chemotherapy. Opacities just a few millimetres across can be easily visualized. Cavitation is occasionally present, usually indicating metastases from squamous cell carcinoma.

Pleura

Pleural metastases are often from breast carcinoma, and may be visualized as mass lesions, though the most common manifestation is a pleural effusion, masking the underlying pathology.

Lymph nodes

CT is accurate in the detection of enlarged hilar and mediastinal lymph nodes. (CT will detect nodes I cm in size and smaller, but nodes < I cm are less likely to be metastatic.)

Lymphangitis carcinomatosa — secondary deposits in central lymph nodes may produce lymphatic congestion with a linear pulmonary pattern radiating outwards from the hilar glands, septal lines and pleural effusions.

Local invasion

Pericardium to give malignant pericardial effusion; superior vena cava compression or obstruction; phrenic nerve paralysis; Pancoast’s tumour.

Skeletal system: ribs, thoracic spine, shoulder girdle

Deposits may be lytic, e.g. from breast, sclerotic from prostate, or mixed

Fig. Widespread pulmonary metastases.

 

Fig.  CT thorax showing multiple small metastases.

 

PNEUMONIA

Pneumonia, an inflammatory reaction in the lungs, occurs either as a primary infection of the lungs, or secondary to bronchial obstruction.

Primary pneumonia. Inflammation arising in a normal lung.

Secondary pneumonia. Caused by:

•  occluded bronchus from bronchial carcinoma or foreign body;

•  aspiration from pharyngeal pouch, oesophageal obstruction;

•  underlying lung pathology: bronchiectasis, cystic fibrosis.

Lobar pneumonia. Inflammatory changes confined to a lobe, classically due to Streptococcus pneumoniae.

Bronchopneumonia. Produces bilateral multifocal areas of consolidation.

RADIOLOGICAL FEATURES

On a plain film, it is generally not possible to diagnose the infecting agent from the type of shadowing.The affected part of lung assumes an increased density with inflammatory exudate and fluid occupying the alveolar space. Air still remaining in the affected bronchi appears as linear lucencies (consolidation with air bronchogram). Consolidation may persist, often after the patient’s symptoms have improved. CT is not required for primary pneumonia, but allows assessment of complications.

TYPES  OF  PNEUMONIA

•  Viral pneumonia: most common pneumonia in children.

•  Streptococcal pneumonia: commonest cause of bacterial pneumonia.

•  Mycoplasma pneumonia (primary atypical pneumonia): commonest cause of non-bacterial pneumonia, often with slow resolution.

•  Staphylococcal pneumonia: most frequent cause of bronchopneumonia and secondary invader in influenza.

•  Klebsiella pneumonia: predominantly seen in elderly, debilitated patients.

•  Legionella pneumonia: a rapidly progressive pneumonia, often in the lower lobes and associated with systemic involvement affecting other organs, especially the liver and kidneys.

•  Pneumocystis carinii pneumonia: typically affects patients with acquired immune deficiency syndrome (AIDS) or those who are immunosup-pressed; diffuse perihilar changes progress to alveolar consolidation.

Radiation pneumonia: pneumonic consolidation arising in the field of radiotherapy.

Fig. Right upper lobe pneumonia bounded inferiorly by the horizontal fissure. Blunting at the right costophrenic angle is due to a pleural effusion.

 

TUBERCULOSIS

Tuberculosis is a chronic infection caused by Mycobacterium tuberculosis, affecting mainly the respiratory tract, though it can involve any system in the body. The immigrant population, debilitated or immunosuppressed patients are all prone to the infection.

RADIOLOGICAL FEATURES

In primary tuberculosis the following may be present on a chest X-ray:

•   Area of peripheral pneumonic consolidation (Ghon focus) with enlarged hilar mediastinal glands (primary complex). This usually heals with calcifi­cation.

•   Areas of consolidation which may be small, lobar or more extensive throughout the lung fields.

Postprimary tuberculosis or reactive tuberculosis:

•   Patchy consolidation, especially in the upper lobes or apical segments of the lower lobes, often with cavitation.

•   Pleural effusions, empyema or pleural thickening.

•   Miliary tuberculosis: discrete I-2 mm nodules distributed evenly throughout the lung fields due to haematogenous spread.

•   Mediastinal or hilar lymphadenopathy is not a feature, except in acquired immune deficiency syndrome (AIDS) patients.

As healing progresses, features that may be recognized are: fibrosis and volume loss; calcified foci; tuberculoma: a localized granuloma often containing calcification; pleural calcification.

 

Fig. Manifestations of pulmonary tuberculosis

 

Fig. Old healed calcified tuberculous foci.

 

BRONCHIECTASIS

Bronchiectasis is defined as a condition in which there is an irreversible dilatation of the bronchi. The main aetiological factors appear to be obstruction leading to distal bronchial dilatation and infection causing permanent bronchial wall damage.

PRESENTATION

Cough with purulent sputum; haemoptysis; recurrent chest infections.

RADIOLOGICAL  FEATURES

The chest film may be entirely normal. Bronchiectasis is commonest at the lung bases and a chest X-ray may reveal the following features.

•  Cylindrical bronchiectasis: dilated bronchi may be visible as parallel lines (representing the bronchial walls) radiating from the hilum towards the diaphragm.

•  Cystic bronchiectasis: terminal dilatation may be visualized as cystic or ring shadows, sometimes with fluid levels.

•  Pneumonic consolidation.

•  Fibrotic changes.

High-resolution CT unequivocally demonstrates bronchial dilatation and thickened bronchial walls. It can also define which lobes are affected, especially important to identify if surgery is needed. On CT, the following additional features may be observed:

•  bronchi visible peripherally;

•  bronchus larger in diameter than the adjacent pulmonary artery branch.

COMPLICATIONS: Empyema; cerebral abscess; amyloid.

CAUSES

Childhood infections: following measles and whooping cough complicated by pneumonia.

Aspergillosis: hypersensitivity reaction in the bronchial walls in asthmatics resulting in bronchiectasis which affects proximal airways.

Bronchial obstruction: foreign body, neoplasm or tuberculosis.

Cystic fibrosis: viscid sputum leading to bronchial obstruction and bronchiectasis.

Congenital: Kartagener’s syndrome (dextrocardia, sinusitis and bronchiectasis).

 

Fig. Cystic bronchiectasis: ring opacities at the right base.

 

Fig. Bronchography: now an obsolete technique but elegantly demonstrates cylindrical bronchiectasis with dilatation of the lower lobe bronchi.

Fig. CT scan of thorax: bronchiectasis confined to the lingula.

 

 

PLEURAL EFFUSION

Pleural effusion, a fluid collection in the space between the parietal and vis­ceral layers of the pleura, usually contains serous fluid, but may have differing contents.

Haemothorax:	Blood, usually following trauma.
Empyema:	Purulent fluid from extension of pneumonia or lung abscess.
Chylothorax:	Chyle from rupture of the thoracic duct or sec- ondary to malignant invasion.
Hydropneumothorax:	Fluid and air.

Haemothorax:                   Blood, usually following trauma.

Empyema:                        Purulent fluid from extension of pneumonia or

lung abscess.

Chylothorax:                     Chyle from rupture of the thoracic duct or secondary to    malignant invasion.

Hydropneumothorax:         Fluid and air.

 

RADIOLOGICAL  INVESTIGATIONS: Chest film; Ultrasound; CT.

 

RADIOLOGICAL  APPEARANCES

 

Pleural fluid, in the erect position, gravitates to the lower-most part of the thorax with the following features on a chest X-ray:

•  homogeneous opacification, generally of the same density as the cardiac shadow;

•  loss of the diaphragm outline;

•  no visible pulmonary or bronchial markings;

•  concave upper border with the highest level in the axilla.

As the fluid collection grows in size, the underlying lung decreases in volume and retracts towards the hilum. Initially the fluid accumulates in the posterior, then the lateral costophrenic space. When fluid is detected on a standard PA chest film, by blunting of the costophrenic angle, the pleural effusion will already contain 200-300 ml. With larger effusions, there is a mediastinal shift to the opposite side.

Subpulmonary effusion. Caused by fluid accumulating between the diaphragm and the inferior part of the lung. The upper margin of the shadow of the fluid runs parallel to the diaphragm and on the PA chest film mimics a high diaphragm.

Loculated effusion. Fluid can loculate in the fissures or against the chest wall, and this is occasionally seen in cardiac failure.

•  Ultrasound is a highly sensitive examination in detecting pleural fluid.

•    CT may also demonstrate pleural effusions and visualize underlying abnormalities.

Fig. Large left pleural effusion

Fig. Ultrasound showing the effusion (black) surrounding the retracted lung (arrows).

PNEUMOTHORAX

A pneumothorax occurs when air enters the pleural cavity by a tear in either the parietal or visceral pleura; the lung subsequently relaxes and retracts to a varying extent towards the hilum. Small pneumothoraces are difficult to diagnose and usually become more prominent on expiratory films.

RADIOLOGICAL  FEATURES

Pneumothorax is best demonstrated on an underpenetrated chest film. The following may be seen.

•  Lung edge: a thin white line of the lung margin, the visceral pleura.

•  Absent lung markings between the lung edge and chest wall.

•  Mediastinal shift: when a tension pneumothorax develops.

CAUSES

•  Iatrogenic (one of the commonest causes): following lung biopsy, chest aspiration, thoracic surgery and central line insertion.

•  Spontaneous: most common in tall, thin, young males; usually due to rupture of a small pleural bleb.

•  Trauma: stab wounds, rib fractures. Surgical emphysema is commonly associated with air tracking along the muscle planes of the chest wall.

•  Pre-existing lung disease: increased incidence of pneumothorax with underlying lung disease such as emphysema, cystic fibrosis or interstitial lung disease.

COMPLICATIONS

•  Tension pneumothorax: a tear in the visceral pleura may act as a ball valve allowing air to enter the pleural cavity during each inspiration, and none to escape during expiration. Positive pressure builds up, resulting in a dramatic shift of the mediastinum away from the side of the pneumotho­rax. This is a medical emergency, as death can rapidly ensue from respira­tory distress and diminished cardiac output.

•  Hydropneumothorax: fluid in a pneumothorax.

TREATMENT

Generally, a small pneumothorax with less than 20% collapse of the lung requires no treatment. Pleural air will reabsorb with subsequent lung expansion. Larger pneumothoraces can be treated by aspiration or insertion of a chest drain with an underwater seal. Follow-up films are required to ensure complete resolution of the pneumothorax.

Fig.  Right pneumothorax: there are no visible markings beyond the lung edge.

Fig. Tension pneumothorax with complete collapse of the right lung and mediastinal shift to the left.

Fibrosing alveolitis

Fibrosing alveolitis is a disease of unknown aetiology, but probably auto­immune, in which an inflammatory reaction in the alveolar wall leads to pulmonary fibrosis. It is more common in males, and in the 40-70 age group. Prognosis is poor with a greater than 50% mortality over 5 years.

PRESENTATION: Progressive dyspnoea; cough; clubbing.

RADIOLOGICAL  FEATURES

In early disease, the chest X-ray may be normal, but as fibrosis progresses the following features may exist.

•  Fine nodular and streaky linear shadowing (reticulonodular pattern) starting at the bases but may involve all the lung fields.

•  Honeycomb pattern in severe disease, with small cystic spaces and coarse reticulonodular shadowing.

•  Reduction in lung volume.

•  Poor definition of the cardiac outline due to adjacent lung fibrosis.

•  Dilatation of pulmonary arteries with right ventricular enlargement and pulmonary hypertension.

High-resolution CT sections define lung parenchymal changes earlier and the examination is more precise than a chest X-ray. CT is effective in monitoring progress of the disease.

CAUSES  OF  LUNG  FIBROSIS

•  Sarcoidosis.

•  Cystic fibrosis.

•  Pneumoconiosis.

•  Rheumatoid lung.

•  Systemic sclerosis.

•  Drugs: nitrofurantoin, cyclophosphamide.

COMPLICATIONS

•  Pneumothorax.

•  Cor pulmonale.

TREATMENT

•  Steroids.

•  Immunosuppressive therapy.

Fig. CT thorax: fibrosing alveolitis with coarse linear fibrotic strands.

Fig.

Normal CT

thorax at the same level.

Fig. Fibrosing alveolitis: extensive reticular shadowing throughout both lungs

EMPHYSEMA

Emphysema is a condition in which there is an increase in the size of the air spaces, with dilatation and destruction of lung tissue distal to the terminal bronchiole. Cigarette smokers and coal miners have a higher incidence, and rarely there may be an association with a-antitrypsin deficiency (in which emphysema predominantly affects the lower lobes).

RADIOLOGICAL  FEATURES

The chest X-ray may be entirely normal despite severe debility of the patient. In advanced emphysema the following may be found.

Hyperinflation of the chest

•  Low flat diaphragms with limited excursion in inspiration and expiration.

•  Increase in the AP diameter of the chest with an expansion in the ret­rosternal clear space (barrel chest).

•  Thin, long and narrow appearance to the heart shadow, likely to be from overinflation and low diaphragms, rather than an actual change in heart size.

Vascular changes

•  The lungs are generally unevenly affected with an abnormal distribution of pulmonary vasculature; blood vessels are attenuated, with loss of the normal smooth gradation of vessels from the hilum to the periphery.

•  Pulmonary hypertension leading to cor pulmonale. The proximal pul­monary arteries progressively enlarge and right-heart failure develops.

Bullae

Cyst-like spaces often develop from rupture of distended alveoli. On a chest film, they are seen as translucent areas with their walls shown as thin curvilinear hair-line shadows. They vary in size from a few centimetres in diameter to occupying a large part of the hemithorax, displacing and com­pressing adjacent normal lung.

TERMINOLOGY

The term’ emphysema’ is also used in:

•  Mediastinal emphysema: air within tissue planes of the mediastinum.

•  Surgical emphysema: air tracking along the soft-tissue planes; in the chest, this may be found after thoracic surgery or a pneumothorax.

Obstructive emphysema: a bronchus partially occluded by a mass or foreign body causing a ball valve obstruction.

 

Fig. CT thorax: multiple destructive areas resulting in bullae of varying sizes

 

Fig. Emphysema: overinflation of the lungs, flattened diaphragms, bullae and a small cardiac shadow.

 

PNEUMOCONIOSIS

Pneumoconiosis is a condition caused by the inhalation of dust into the lungs. A history of dust exposure is present.

RADIOLOGICAL  APPEARANCES

Appearances depend on whether the dust is active or inactive.

Active dust: Silica and coal dust are potent producers of diffuse lung fibrosis, although in the early stages small lung nodules are a characteristic feature.

Inactive dust: Iron oxide, calcium compounds and barium produce a fine nodular pattern, due to deposits of dust particles.

Organic dust:     Exposure can also cause lung fibrosis examples being:

•  Bird-fancier’s lung: pigeon and budgerigar excreta;

•  Farmer’s lung: mouldy hay;

•  Bagassosis: sugar-cane dust.

COMPLICATIONS

•  Progressive massive fibrosis.

•  Caplan’s syndrome.

•  Emphysema.

•  Cor pulmonale.

ASBESTOS EXPOSURE

RADIOLOGICAL  APPEARANCES

With previous exposure to asbestos, the following may be seen on a chest X-ray:

•  Focal pleural plaques: often the earliest finding, seen lying adjacent to ribs.

•  Calcified pleural plaques: bilateral diaphragmatic calcifications are very suggestive of previous asbestos contact.

•  Diffuse pleural thickening.

•  Pleural effusions: often bilateral.

•  Pulmonary fibrosis, especially basal though the whole lung, may be involved leading to cor pulmonale. Reticular shadowing commences at the bases and may obscure the sharp outline of the heart border.

•  Malignant disease.There is a much higher incidence of:

mesothelioma (chest and peritoneal);

bronchial carcinoma,

laryngeal carcinoma.

 

Fig.  Coal worker’s pneumoconiosis: coarse nodular shadowing.

Fig. Calcined pleural plaques in asbestos exposure.

 

ELEVATED DIAPHRAGM

The diaphragm consists of a thin sheet of muscle with a smooth upward convexity, the right usually lying in a higher position than the left. On a chest film, the inferior surface of the diaphragm is not visualized as it blends with the surfaces’of the liver and spleen.

CAUSES  OF  A  UNILATERAL  ELEVATED  DIAPHRAGM

•  Above diaphragm: phrenic nerve palsy; infiltration from bronchial carci­noma or mediastinal tumour.

•  Diaphragm: eventration, more common on the left and results from deficiency or atrophy of muscle.

•  Below diaphragm: right diaphragm elevation; liver or subphrenic abscess, liver secondary deposits.

CAUSES  OF  BILATERAL  ELEVATED  DIAPHRAGMS

•  Obesity.

•  Hepatosplenomegaly.

•  Within the abdomen: ascites, pregnancy, abdominal masses.

OPAQUE HEMITHORAX

Complete opacification of a hemithorax is encountered in the following conditions. (Mediastinal shift is assessed by the position of the trachea and the heart.)

With mediastinal shift away from opaque hemithorax: pleural effusion; large pleural effusions may occupy the whole of the hemithorax.

With mediastinum central: consolidation; in severe pneumonia, consolidation may render the whole lung opaque.

With mediastinal shift towards opaque hemithorax:

•   Lung collapse: most commonly occurs from total occlusion of a main bronchus either by a central bronchial carcinoma or a postoperative mucus plug. The lung collapses and is devoid of air, hence the appearance of a dense hemithorax.

Post pneumonectomy: after resection of a lung, the empty hemithorax fills with fluid. Gradual reabsorption with a fibrotic reaction eventually results in opacification with a significant mediastinal shift towards the pneumonectomy.

Fig. Elevated right diaphragm

Fig.  Complete opacification of the right hemithorax: collapse of the right lung with significant mediastinal shift to the right (note position of the trachea and cardiac shadow).

HILAR LYMPHADENOPATHY

Hilar lymphadenopathy may cause enlargement of the hilar shadows, the lymph nodes appearing as well-defined, lobulated masses. Nodal enlarge­ment has to be differentiated from hilar vascular prominence (as in pul­monary hypertension). Difficulty may be encountered in distinguishing between them on chest radiography, though CT with contrast or MRI accurately identifies the abnormality.

CAUSES  OF  BILATERAL  HILAR  GLAND  ENLARGEMENT

•  Sarcoidosis: commonest cause, usually resolving spontaneously.

•  Lymphoma: mediastinal glands are more frequently involved than hilar.

•  Tuberculosis: enlargement is usually asymmetrical and often associated with mediastinal glandular involvement.

•  Metastases.

CAUSES  OF  UNILATERAL  HILAR  GLAND  ENLARGEMENT

•  Bronchial carcinoma.

•  Lymphoma.

•  Tuberculosis.

LUNG ABSCES

A lung abscess is a localized necrotic, cavitating lesion due to a pyogenic infection. Secondary abscess formation may occur from aspiration under anaesthesia, inhalation of vomit or foreign body, oesophageal disease such as achalasia and carcinoma of the oesophagus or septic material aspiration from upper-airway passages.

RADIOLOGICAL  FEATURES

Abscess formation may initially start as an area of pneumonic consolida­tion (especially Staphylococcus aureus or Klebsiella pneumoniae) with subse­quent development of cavitation. A fluid level is ofteoted in the abscess.

DIFFERENTIAL  DIAGNOSIS  OF  A  CAVITATING  LESION

•  Carcinoma: primary bronchial carcinoma is the commonest cause; soli­tary cavitating secondary deposit. A benign cavity has a central cavity and a regular wall whereas a malignant one has an eccentric cavity with an irregular wall.

•  Tuberculosis.

•  Cavitating pulmonary infarct, haematoma or infected bulla (rare).

Fig. Bilateral hilar lymphadenopathy.

Fig. Lung abscess: cavitating lesion in the right mid-zone with a fluid level

 

FIBROSIS

Fibrosis may affect predominantly the apices and upper zones, with sparing of the lower zones in the following conditions:

•  Tuberculosis: associated with calcified areas and pleural thickening.

•  Sarcoidosis: hilar lymphadenopathy may also be present.

•  Radiotherapy: usually following treatment for carcinoma of the breast.

•  Ankylosing spondylitis: fibrosis usually occurs when the spinal disease is severe.

•  Chronic extrinsic allergic alveolitis: hypersensitivity reaction to inhala­tion of specific antigens, e.g. from pigeons and budgerigars; the chest X-ray is often normal but may show patchy consolidation in the acute stages, but in chronic disease fibrotic shadowing is predominantly in the upper zones.

Fibrosis in the lower zones may obscure the heart border and produce a ‘shaggy heart’ appearance. Fibrosis predominantly affects the lower zones in:

•  Bronchiectasis or long-standing infection.

•  Cryptogenic fibrosing alveolitis.

•  Rheumatoid arthritis.

•  Radiotherapy: usually following treatment for carcinoma of the breast.

•  Asbestos exposure.

•    Scleroderma: an autoimmune disease with fibrosis of interstitial lung tissue, predominantly basal but may involve the whole lung. The disease commonly affects the joints, skin, gut and respiratory tract.

Fig. Upper zone fibrosis from tuberculosis.

Fig.  Lower zone fibrosis due to bronchiectasis

MEDIASTINAL MASS

The mediastinum is that part of the chest bounded by the sternum at the front, thoracic spine at the back and laterally by the medial surfaces of vis­ceral pleura. It can be divided into: anterior mediastinum: anterior to the pericardium; middle mediastinum: the heart, aortic root and pulmonary vessels; posterior mediastinum: behind the posterior pericardial surface.

 

 

 

Fig. Mediastinal compartments. Although the mediastinum is categorized into compartments, masses may freely cross from one part to another.

 

RADIOLOGICAL  FEATURES

Usually, a mediastinal mass is suspected on a plain chest film; a lateral film may be helpful; further evaluation is carried out by CT/MRI for anatomical localization. The presence of cystic lesions, calcification, fat and vascular structures are all more accurately assessed than by plain films.

• Anterior mediastinal masses (three Ts—thyroid, thymus and teratodermoids)

Retrosternal thyroid: the mass is well defined and may be lobulated. Extension into the mediastinum is to a varying degree up to the carina.
Thymic tumours: these may be benign or malignant and frequently associated with myasthenia gravis.

Teratodermoids: these tumours are usually benign but have a malignant potential. Occasionally fat, rim calcification, bone fragments and teeth may be identified.

• Middle mediastinal masses

Lymphadenopathy: lymphoma, metastases, sarcoid or tuberculosis.

• Posterior mediastinal masses

Neurogenic tumours arising from intercostal nerves and sympathetic chain.

Neurofibromas (nerve sheath tumours).

Ganglioneuroma (sympathetic nerve cell tumours).

 

Fig. Widening of the upper mediastinum from a retrosternal thyroid.

Fig.  CT upper thorax: retrosternal thyroid causing tracheal narrowing (-♦). Note calcined areas in the mass.

RIGHT LOBE COLLAPSES

The right upper-lobe collapses with movement of the horizontal fissure upwards, pivoting at the hilum in both the PA and lateral projections. The collapsed lobe assumes an increased density at the right apex, its lower border being sharply defined by the horizontal fissure. The hilum may be elevated.

Fig.  Right upper-lobe collapse due to a mass at the right hilum.

Fig. Movement of the fissures in right upper-lobe collapse

The middle lobe is relatively small. On the PA view, middle-lobe collapse produces only minor changes, with some increased density lateral to the right cardiac border with blurring of the cardiac outline (silhouette sign). It is most accurately evaluated using the lateral projection, where the col­lapsed lobe is seen as a triangular opacity projected over the cardiac shadow.

Fig. Right middle-lobe collapse. PA view. Note loss of right heart border.

Fig. Lateral view showing the collapse projected over the cardiac shadow (Arrows)

 

Fig. Movement of fissures in right middle-lobe collapse

 

LEFT LOBE COLLAPSES

The lobe collapses in a different fashion to the right upper lobe. Movement of the oblique fissure is forwards and the collapsed lobe lies anteriorly against the chest wall, giving rise to a hazy, ill-defined opacity in the upper and mid-zones on the PA projection

Fig.  Left upper-lobe collapse with hazy ill-defined shadowing in the left upper and mid-zone.

 

Fig.  Lateral view shows the lobe collapses anteriorly. (Arrows.)

 

 

Fig.  The oblique fissure moves forwards in left upper-lobe collapse.

 

 

RIGHT/LEFT LOWER-LOBE COLLAPSE

The lower lobes collapse medially and posteriorly. The oblique fissure moves backwards maintaining the same slope. On the PA film, left lower-lobe collapse is seen as a triangular area projected through the cardiac shadow.

 

 

Fig.  Bilateral lower-lobe collapse (arrows), the left more clearly defined

 

Fig. The oblique fissure moves backwards in lower lobe collapse.