Pleural effusion

PLEURAL EFFUSION

Symptoms:

·         Dyspnoea

·         Sometimes pleuritic pain

Signs

·         Decreased chest expansion on affected side

·         Stony dullness to percussion

·         Diminished breath sounds

·         Reduced tactile vocal fremitus

·         Branchial breathing can sometimes be heard at upper level of the fluid.

Cause: there is a disturbance of the normal fluid dynamics. The parietal pleura is perfused by systemic circulation and the visceral by pulmonary circulation. Fluid filtration into the pleural space is dependent on high systemic capillary pressure, negative intrapleural pressure and pleural oncotic pressure. Generally, fluid is filtered by the parietal pleura and absorbed by the visceral. An effusion can result from:

Increased capillary pressure: eg left ventricular failure

Reduced plasma oncotic pressure: eg hypoalbuminaemia

Increased capillary permeability: eg pleural disease

Obstruction of lymphatic drainage: eg carcinoma of lymphatics.

Transudates

Transudates have low protein (<30g/L) and lactate dehydrogenase (<200iu/L) CAUSED BY CHANGE IN HYDROSTATIC OR OSMOTIC PRESSURE. Examples:

·         Cardiac failure

·         Renal failure

·         Hepatic cirrhosis

·         Ascites (passing through pleuroperitoneal communications)

·         Hypoproteinaemia

·         Myxoedema

Exudates

Exudates have high protein content (>30g/L) and high lactate dehydrogenase (>200iu/L) CAUSED BY DISEASE OF THE PLEURA. Examples:

·         Malignancy (metastatic carcinoma / mesothelioma)

·         Infection (TB / parapneumonic / empyema)

·         Inflammation (SLE / RA / Dressler’s syndrome / Benign asbestos effusion / Rx eg dantrolene)

·         Subdiaphragmatic disease (subphrenic abscess, ascites, pancreatitis).

Investigations

·         CXR shows dense white shadow with concave upper edge, ‘meniscus sign’. Small effusion may require lateral decubitus film to show fluid mobility.

·         CT can be helpful in detecting underlying disease

  Aspiration

o   APPEARANCE

o   Should be straw coloured. Blood suggests malignancy, infarction or severe inflammation. Pus suggests empyema. Milky white suggests chylothorax and frank blood a haemothorax.

o   BIOCHEMISTRY

o    Transudate or exudate (protein / LDH)  

o   ↓glucose suggests infection or connective tissue disease

o   ↑Amylase = pancreatitis or adenocarcinoma

o   CYTOLOGY

o   Lymphocytes (TB / malignancy)

o   Neutrophils (infection / inflammation)

o   Look for malignant cells eg mesothelioma.

o   MICROBIOLOGY

o   TB / Bacteria

·         Biopsy with abram’s needle can be sent for histology (carcinoma / mesothelioma / TB) and microbiology (TB).

Treatment

Transudates à correct underlying cause such as heart failure, hypoproteinemia. Further investigation not usually necessary.

Exudates àmay require draining (no more than 2L daily) if symptomatic.  Can be aspirated with the diagnostic tap or a chest drain may be inserted.  Empyema should be drained with US guidance. Fibrinolytic agent may be used to improve drainage and remove adhesions. Recurrent malignant effusions can be treated with talc pleurodesis.