Each lung is covered by a double-layer serous membrane with a potential space between the two layers. The outer or parietal layer covers the inside of chest wall and superior surface on diaphragm and is sensitive to pain; the inner or visceral wall covers the lungs and its fissures but insensitive to pain.
The parietal layer is supplied by blood vessels, lymphatics and nerves from the intercostal spaces while visceral layer is supplied by bronchial vessels and it has sympathetic nerve supply only. Parietal layer of the superior diaphragmatic surfaces is supplied by phrenic nerve from the neck but peripheral areas of diaphragm are supplied by intercostal nerves.
Normal intrapleural pressure varies with phases of respiration. During inspiration it is 4 to 8 cm of water pressure and -2 to -4 cm. at the end of expiration. The pleural space contains a thin film of pleural fluid which functions as lubricant.
The pleural cavity may be affected due to the various causes. When there is fibrinous inflammation it is called dry pleurisy, but when there is collection of fluid between pleural layers, it is called pleural effusion. Pleuro-pericarditis may sometimes occur due to contiguous affections from pericardial disease.
1. Acute Fibrinous Pleurisy:
(Syn: Dry Pleurisy or Pleuritis)
It is an inflammation of pleural layers almost always due to one of the causes mentioned above. However, tuberculosis is the most common cause of pleurisy, especially in developing countries.
Sudden onset of pain in the chest wall aggravated by coughing or deep breathing, with or without fever and chill usually heralds the episode. Pressure on chest wall may cause considerable discomfort. Diaphragmatic pleurisy causes pain referred to the tip of shoulder (via phrenic nerve supply) or upper abdomen via lower intercostal nerves.
Classical signs are:
(a) Diminished movement of affected side of chest.
(b) Pleural friction rub.
(a) Rest in bed is essential along with analgesics, sedatives and codiene syrup to control cough. Specific therapy depends on underlying aetiology.
(b) Kaolin poultice may give relief.
(c) Strapping of chest wall is occasionally required if pain is severe in spite of the above measures.
2. Pleural Effusion:
Pleural effusion is a collection of fluid in the pleural cavity most commonly due to tubercular- aetiology in our country but other causes should also be excluded. The tubercular focus may be either due to primary complex, or post-primary.
In children and adolescents a pleural effusion may be the only manifestation of primary tuberculosis, without any warning sign of chest pain or fever. Sometimes it follows primary tuberculosis, due to hypersensitive reaction of the to the primary infection.
In infants and children below three years pleural effusion as a manifestation of primary complex is rare, it is found usually after 3 years, and mostly in the age group of 10 to 12 years. Pleural effusion in this age group demands more attention as it may lead to secondary dissemination by blood-stream. Many patients of adult tuberculosis give past history of pleural effusion treated inadequately.
In elderly and heavy smokers possibility of new growth should be suspected, but still in developing countries tuberculosis may be the cause.
It usually starts with pleuritic pain if the volume of fluid is small but with further collection of fluid visceral and parietal pleura are separated and the pain subsides as pleuritic pain is caused by rubbing together of the two layers of pleura.
The symptom depends largely on the amount of fluid collected resulting in collapse of the underlying lung, and the rate of accumulation of fluid. Large collection of fluid may occur insidiously over a course in the presence of other symptoms like ill-health, weight loss, night sweats or protracted pyrexia of the remittent type for a period of 2 to 3 weeks.
But in case of large collection or rapid collection of fluid, the presenting feature is dyspnoea on slight exertion or even at rest.
Interspaces are fuller and expansion of chest-wall is sluggish on the affected side.
Apex beat of heart and trachea are displaced to opposite side, if the effusion is large, V.F. and V.R. are both diminished. However, the mediastinal shift may not occur if the lung is atelectatic due to presence of underlying new growth. It may even shift to the side of effusion.
Dull percussion note is quite impressive and it is called stony dullness.
Inaudible breath-sound, diminished vocal resonance (V.R.) and sometimes bronchial breathing are found above the level of fluid. Aegophony and whispering pectiroloquy may be heard.
When accumulation of fluid is less than 300 c.c., it may not be detected even by X-ray film. The earliest radiological sign is obliteration of costo-phrenic angle and loss of sharp outline of posterior part of diaphragm in the lateral X-ray film.
With accumulation of more fluid, a dense and uniform opacity is found in the lower and lateral part of hemi-thorax, tapering off above in the axilla, and medially. During resolution, the upper border may be slightly curved. Heart and trachea may be shifted by a large effusion. However, if there is collapse of a lobe, mediastinal shift is not well marked.
Thoracentesis should be done in all cases to establish the aetiological diagnosis unless the fluid is too small. Chemical, bacteriological and microscopic examination of the fluid is necessary.
Routine tests consist of estimation of protein content, cytology search for AFB and culture of organism. Presence of blood suggests trauma, neoplasm or infarction.
Lymphocytosis favours tuberculous aetiology. Malignant cells may be searched for in suspicious cases. Special tests are often done, e.g., glucose and amylase estimation. Glucose is less than 40 mg in empyema, tuberculosis and rheumatoid arthritis.
Amylase is raised in pancreatitis. Triglycerides are raised in chylous effusions. Lactic dehydrogenase level is less than 200 I.U. in transudates.
In case of large collection of fluid with dyspnoea, at least a litre of fluid should be aspirated slowly to relieve symptoms. Fluid of tubercular pleural effusion, usually clots on standing, specific gravity more than 1015, protein content more than 3 g. per 100 c.c. of fluid, and cells are chiefly lymphocytes. At least 30 ml. of fluid should be collected in a sterile test tube for bacteriological and chemical tests and about 50 to 100 ml. in a citrated container to detect the presence of malignant cells.
Rapid aspiration of large quantities of fluid should not be done as it may cause pulmonary oedema on the opposite side. Purulent fluid should be surgically drained.
Repeated aspiration may be necessary if reaccumulation continues.
If frank blood is found in the pleural fluid, possibility of trauma, malignancy and pulmonary infarction is to be considered. It is only by diagnostic aspiration that presence of blood or chyle can be detected. Damage to thoracic duct results in chylo-thorax. It may occur due to blunt injury, intra-thoracic malignancy, filariasis or after thoracic surgery.
Chemical analysis confirms the presence of true chyle. Pseudochylous effusion may be due to cholesterol-rich fluid occurring in long standing effusion.
Chemical examination of fluid gives additional help, e.g. higher pleural fluid amylase than blood in pancreatic effusion, lower fluid glucose (less than 12 to 16 cm) in effusion of rheumatoid origin or higher lactic dehydrogenase (L.D.H.) in exudative effusion, if protein content is not decisive.
It is to be kept in mind, however, that negative findings in X-ray, sputum, pleural fluid do not exclude the aetiology of pulmonary tuberculosis in young adults. To clinch the diagnosis pleural biopsy from the parietal pleura should be taken when there is presence of fluid to avoid injury to the lung. Abraham’s or Cope’s needle is generally used.
Pleural thickening, pneumonic consolidation, atelectasis should be carefully excluded. If collection of fluid is massive and very rapid after aspiration, one should remember malignancy, especially in persons over 40 years of age.
Treatment depends on aetiological diagnosis. If aetiology is uncertain pleural aspiration is necessary. If fluid is too small, pleural biopsy may also be considered.
3. Tuberculous Effusion:
This should be treated as a case of pulmonary tuberculosis. Inadequate therapy may lead to pulmonary tuberculosis within five years or even later on.
Removal of available fluid by repeated aspirations (500 to 1000 ml per day) in two or three sitting prevents adhesions. However, careful use of corticosteroids for four to six weeks, along with A.T.T., often gives complete resolution. In developing countries especially in rural areas, this method of therapy is preferred by many as risk of empyema due to repeated aspiration can be avoided.
In malignant effusion repeated aspiration may be necessary as fluid reaccumulates quickly causing dyspnoea.
Radiotherapy of the hemithorax and cytotoxic drugs should be used.
4. Empyema Thoracis:
When the pleural effusion is purulent the diagnosis is empyema thoracis. The pus may be thin opalescent fluid or it may be so thick that it is difficult to draw it out with aspirating needle. Sometimes the empyema is loculated i.e. encysted empyema.
Similar to the causes of pleural effusion. Rupture of sub-diaphragmatic abscess, amoebic liver abscess, bacterial pneumonias advanced bronchiectasis, penetrating injury of chest wall and tuberculosis are common causes.
Both parietal and visceral layers of the pleura are inflammed. The shaggy, rough surface is covered with purulent exudate and, if not properly and quickly treated, there is progressive fibrosis leading to collapsed lung which cannot expand at all.
The empyema may become communicated with bronchus leading to broncho-pleural fistula. Thus air enters into the pleural space containing pus and some pus is coughed out. The result is pyopneumothorax.
The clinical features are similar to pleural effusion but the patient has high swinging temperature sweating, rigor and toxaemia. Physical signs are not different from pleural effusion. Small encysted effusion can be detected by radiology.
1. High polymorph leucocytosis.
2. Thoracocentesis-aspiration of purulent fluid establishes the diagnosis.
Acute cases will require supportive therapy, proper intensive antibiotic therapy and drainage of pleural space by intercostal tube connected to water seal collecting bottle, as done in cases of tension pneumothorax. The intercostal tube is introduced in the most dependent part.
Sensitivity test of organisms cultured from aspirated pus is the best guide to decide antibiotic therapy. Till the report is at hand, high doses of penicillin, ampicillin or amoxycillin may be started parenterally. Watch carefully the amount of drainage and the consistency of the pus, as well as the general condition. If progress is not satisfactory within a week, surgical drainage must be considered, i.e. rib resection and drainage may be necessary. Chronic empyema is purely a surgical problem.