Disease of the Pleura and Pulmonary Cysts

Inflammation of the Pleura is called Pleurisy. In dry Pleurisy, the pleural surfaces are inflated without fluid in between them. In many cases pleurisy is associated with effusion. Both dry pleurisy and pleural effusion may develop at different stages of the same disease process.

Dry or fibrinous pleurisy : The pleura gets involved from the disease of the underling lung. Trauma to the chest may also lead to Pleurisy. The suggestive symptom is the catching pain felt acutely over the affected area by inspiratory movements thought about by deep breathing, coughing or sneezing. Its etiology are as follows: Pulmonary tuberculosis, pneumonia, bronchogenic carcinoma, pulmonary infarction, connective tissue disorders (such as systemic lupus erythematosus, polyarteritis nodosa, and rheumatoid disease), rheumatic fever, viral infections (especially Coxsackie [Bornholm disease], hepatopulmonary amoebiasis , and uraemia.

The physical examination reveals reduction of movement on the affected side and the presence of pleural friction rub on auscultation. Pleural rub has a superior grafting quality. The rub is heard better by gentle pressure of the chest piece of the stethoscope on the chest wall. Unlike rales, it is not altered by coughing. With the development of pleural effusion, the rub may disappear in most cases. Pleural rub will be distinguished from crepitations and sounds arising from movements of the chest wall. Other painful conditions like Pneumonia, myocardial infarction, and herpes Zoster have to be differentiated from pleurisy.

Pleural effusion : In this condition, fluid accumulates between the two layers of the pleura. Normally, pleura contains only a small amount of fluid. The pleural fluid remains in dynamic equilibrium with blood. Movements of the lung favor the movement of the fluid in and out of the pleural space. In most of the disease states, absorption of the fluid is reduced. The fluid may be contained in the general pleural space or it may be located in the interlobar fissure, infrapulmonary space or may remain adjacent to the mediastinum. The fluid progressively compresses the subjacent lung which undergoes collapse.

The development of symptoms depends upon the speed of accumulation of fluid and its quantity. Common symptoms include dyspnea, pleuritic pain, or symptoms of the underlying disorder. High fever may occur in acute pyogenic infections. Tuberculosis may be associated with lower grades of fever. Pleural fluid is clinically detectable only when it is about 500ml in volume but radiologically it may be detected even when the volume is only 350 ml. A fully developed moderate or massive effusion reveals fullness of the intercostal spaces and restriction of respiratory movements of the same side. Midline structures are shifted to the opposite side. Percussion elicits stony dullness with the highest level in the axilla and lower levels in front and back (S-shaped curve of Ellis). This is the most constant physical sign. The Traube's space, which is the area overriding the gas bubble or the stomach, is obliterated in left-sided effusion. Breath sounds, vocal femitus and vocal resonance are diminished or absent. Aegophony may be present above the level of effusion. At times bronchial breathing may be heard over a pleural effusion.

Complications include: Respiratory embarassment, massive bilateral effusions which may be fatal due to respiratory failure, secondary infection of the pleural fluid which converts it into empyema, organization of fibrin from the fluid on the surface of the collapsed lung (cortication) that prevails re- expansion, and fibrosis of the pleura and obliteration of the pleural space (fibrothorax) which develop as a sequel to long standing pleural effusions.

Radiographic appearance: If the fluid volume is small only the costophrenic angles are obliterated. As the fluid accumulates further, it throws a triangular lateral opacity obscuring the hemidiaphragm. Large pleural effusions shift the midline structures to the opposite side. An interlobar effusion in the oblique fissure produces an elongated cigar-shaped shadow seen better in the lateral view. Fluid in the horizontal fissure throws a rounded shadow seen in the PA-view. The term "vanishing pulmonary tumor" has been used for inter-lobar effusions since they clear up with treatment.
Character of the fluid: Pleural fluids may be transudates or exudates. They differ in physical and biochemical nature. Transudate (Clear, often bilateral, does not clot on standing, specific gravity less than 1015, protein content less than 3g / dL, cells less than 100 / Cmm). Exudate (Opalescent or turbid, unilateral, often clots on standing, above 1015, above 3g / dL, cell count is high).

Congestive Cardiac failure, nephrotic syndrome, hypoproteinemia, constrictive pericarditis, and myxedema may cause transudation into the pleura. Exudates are caused by tuberculosis, Pneumonias, Pulmonary infarction, bronchogenic carcinoma, pleural secondaries, dyscolagenoses and hepatopulmonary amoebiasis. Rare causes include subphrenic abscess, postmyocardial infarction syndrome and acute pancreatitis. Tuberculous effusion is straw-colored. The fluid is hemorrhagic in malignancy and infarction and it is chylous (milky) in lymphatic obstruction due to filariasis and lymphomas. Collection of purulent fluid in the pleura is called empyema.

Microscopy: In acute bacterial infections, neutrophils predominate, lymphocytes predominate in tuberculosis. Eosinophils may predominate in dyscolagenoses and pulmonary infarction. Examination of a wet preparation stained by methylene blue reveal malignant cells in over 90% of cases of malignant effusions. Identification of the nature of the malignant cells is done by Papanicolaou's technique. The nature of chylous fluid is confirmed by demonstrating the presence of fat. Elevated amylase levels are suggestive of acute pancreatitis (500 units / ml of higher). Values ​​of LDH are raised in exudates. Gram-staining, Ziehl-Neelsen staining, and culture help in identifying the causative microbes. When investigations, pleural biopsy may be attempted. Special (Cope's) needles are available for this purpose. Although a positive biopsy is diagnostic, a negative biopsy does not exclude pleural malignancy.

Principles of treatment
Pleural effusion may rarely present as an emergency with respiratory embarrassment. In such cases, emergency measures are required to give relief-especially if the effusion is massive or bilateral. The fluid is aspirated by thoracentesis done in the eighth or ninth intercostal space in the posterior axillary line after anaesthetising the part. Sufficient fluid id removed to relate the distress. Whenever pleural fluid is aspirated, it is also subject to diagnostic investigations.

Elective management
Medical therapy is instituted depending on clinical features and pleural fluid analysis. it is ideal to aspirate the fluid after instituting specific drug therapy. Aspiration is indicated: to make the diagnosis; to alleviate distress and to remove the exudate so as to hasten full recovery of the pleura and avoid complications. It is generally advisable to restrict the volume of fluid removed at one sitting to 1 Liter or less in order to avoid pulmonary edema. Aspiration has to be repeated at times. Two or three aspirations will be adequate in most of the cases of tuberculous effusion. In malignant pleural fluid tend to recollect even after repeated aspirations. Drugs used to be instilled intra-pleasurally with the hope of raising the local concentration of the drug. Intra-pleural administration of drugs should be required only in some rare cases, if proper systemic therapy is given. Sometimes aspiration of the pleural cavity may give rise to complications. These include pleural shock, anaphylactic shock due to anaesthetic, bleeding into the pleural cavity, pulmonary edema, infection, and incidental introduction of air into the pleura.

Cysts of the Lung may be congenital or acquired. Congenital cysts are of three varieties:
1. bronchogenic-these may be solitary or multiple;
2. alveolar cell types-these also may be solitary or multiple; and
3. mixed types having elements of both bronchogenic and alveolar cysts.

These vary in size and may be unilateral or bilateral. They may be located anywhere in the lung. They are filled with fluid at birth, but air enter the cavity later when bronchial communications develop. The cyst may be thick- or thin- walled. Cystic disease of the Lung may occur in association with fibrocystic disease of the pancreas. This is common in Western countries, but is rare in Asia and Africa.

Acquired Cysts
These may be resentous bulous emphysema, subpleural ysts or parasitic cysts, which include hydratid disease and paragonimiasis. The severity of symptoms is determined by the magnitude, size, time of diagnosis, and presence of complications. When the lung parenchyma is grossly reduced, respiratory embarassment and respiratory failure may develop. Super-added infection is common and this is characterized by fever, cough, purulent sputum, and even hemoptysis. Although pulmonary osteoarthropathy may occur, it is a late feature. This is in contrast to bronchiectasis, in which clubbing is an early feature. Potential complications are infection, hemoptysis, Pneumothorax, fibrosis, and Cor Pulmonale.

Cystic disease has to be suspected when a child presents with recurrent respiratory infections. Presence of other congenital abnormalities should strengthen this suspicion. X-ray shows thin-walled cysts, which may be single or multiple. Tuberculosis, bronchiectasis, and Lung abscess have to be differentiated. In congenital cystic lung bronchography delineates the lesions. In the case of single non-communicating cysts, the dye does not enter the cavity.

A large single cysts producing respiratory embarassment from infancy has to be excised. When the cysts are multiple, surgery is contraindicated. Medical management is on the same lines as for bronchiectasis.