Special membranes called the visceral and parietal pleura cover each lung. Visceral pleura intimately surround the lungs like a vest and parietal pleura loosely wraps around them like a shirt. The space between the two membranes is called pleural space. Normally, it contains a small quantity of fluid called pleural fluid for lubrication. Pleural space helps in the smooth expansion of lungs during breathing.
Excessive and abnormal accumulation of fluid in the pleural space is called pleural effusion.
Types of Pleural Effusions
Pleural effusion can be exudative or transudative.
Exudative pleural effusion occurs in response to infection and inflammation. Transudative pleural effusion occurs due to passive accumulation of fluid in pleural space usually as part of generalized edema.
In exudative pleural effusion, the pleural fluid meets at least one of the following criteria
1) The ratio between pleural fluid protein and serum protein is greater
2) The ratio between pleural fluid LDH and serum LDH is greater than 0.6
3) The pleural fluid LDH is more than two-thirds normal upper limit for serum
Transudative pleural effusion does not meet any of the above criteria.
In US, about 1.3 million people are affected annually.
1) Infectious diseases
- Bacterial infections
- Viral infections
- Fungal infections
- Protozoal infections
- Parasitic infections
- Tumor of other organs with spread to pleura (metastatic disease)
- Lung cancer
- Kaposi’s sarcoma
- Breast cancer
- Ovarian cancer
- Stomach cancer
- Benign mediastinal teratoma
3) Gastrointestinal disease
- Intraabdominal abscesses
- Perforation of esophagus
- Diseases of the pancreas
- Diaphragmatic hernia
4) Iatrogenic (physician and treatment induced)
- Radiation therapy
- After liver transplantation
- After lung transplantation
- After abdominal surgery
- After coronary artery bypass surgery
- Endoscopic sclerotherapy for esophageal varices
- Wrong placement of central venous line
- Tran lumbar aortography
- Misplaced nasogastric and nasoenteral feeding tubes
5) Drug (medicine) induced. Many drugs can cause pleural effusions as a side effect, including Amiodarone, Bleomycin, Bromocryptine, Dantrolene, Ergonovin, Ergotamine, Interleukin-2, Isotretinoin, Methotrexate, Methysergide, Metronidazole, Minoxidil, Mitomycin, Nitrofurantoin, Oxprenolol, Practolol, Procarbazine, Propylthiouracil
6) Collagen vascular diseases including systemic lupus erythematosus,
rheumatoid arthritis, Churg-Strauss syndrome, Wegener’s granulomatosis,
Sjogren’s syndrome, and immunoblastic lymphadenopathy
- Exposure to asbestos
- Meig’s syndrome
- Yellow nail syndrome
- Post-cardiac injury syndrome
- Trapped lung
- Electrical burns
- Ovarian hyperstimulation syndrome
- Pericardial disease
- Ruptured ectopic gestation (pregnancy)
- Acute respiratory distress syndrome
- Systemic cholesterol emboli
- Rupture of silicone bag breast implant/prosthesis
- Postpartum pleural effusion
Other diseases and conditions that may contribute to or cause pleural effusions include liver cirrhosis, congestive cardiac failure, myxedema, nephrotic syndrome, pulmonary emboli, peritoneal dialysis, superior vena caval obstruction, urinothorax, fontan procedure, glomerulonephritis, and hypoproteinemia
1) Dyspnoea – difficulty in breathing. It usually denotes a large pleural effusion. It may also be a symptom of underlying severe anemia or cardiac problem.
2) Chest pain – sharp, stabbing, pulling or lightning in character, occurs on the side of pleural effusion. Pain intensity varies with respiration.
3) Cough – may be productive or non productive depending upon the cause of pleural effusion
1) Diminished movements of the chest wall on the side of pleural effusion
2) Deviation of trachea to the opposite side of pleural effusion
3) Absent apical impulse in left sided pleural effusion
4) Decreased vocal fremitus on the side of pleural effusion
5) Stony dull note on percussion till the upper level of pleural effusion on the affected side
6) Decreased or absent breath sounds and decreased vocal resonance on the side of pleural effusion during auscultation.
7) Aegophony on the side of pleural effusion during auscultation
8) Pleural friction rub on the side of pleural effusion during auscultation
The above clinical symptoms and physical findings are common for all causes of pleural effusions. Other specific symptoms and signs from head to foot are present depending upon the underlying disease which caused the pleural effusion, the discussion of which is out of the scope of this article.
1) Chest x-ray PA and lateral views are the gold standard in diagnosing
pleural effusions. However, they may miss minimal effusions.
2) Ultrasound abdomen is very useful to diagnose pleural effusions of less than 100 ml volume
3) CT scan is done wherever needed to further differentiate solid from cystic lesions, effusion from consolidation and parenchymal from pleural diseases. It is also used to assess the effusion with better resolution regarding the underlying pathology.
4) MRI scan is of limited use in imaging the soft tissues surrounding the effusion to assess tumor spread and metastasis in selected cases.
5) Nuclear scans with indium and thallium labeled WBCs are used to assess regarding lung parenchymal infection of pleural infection as the cause of pleural effusion when clinically in doubt and other investigations are not forthcoming.
6) Radiocontrast study of the esophagus is done as an emergency investigation in suspected esophageal rupture
7) Ventilation Perfusion scanning is diagnostic if pulmonary embolism is suspected.
Treatment of Pleural Effusion
Medical management with drugs varies with the nature of the medical illness responsible for pleural effusion. For example, patient requires sensitive antibiotics in case of bacterial pleural effusion, anti tuberculous drugs if tuberculosis is the cause and anti failure medications if congestive cardiac failure is incriminated.
Invasive procedures which can be done to relieve the pleural effusion include
1) Thoracentesis – is to be done if the pleural effusion is large
and symptomatic. It helps to relieve the breathlessness so that patient
is more co-operative for his further evaluation.
2) Tube thoracostomy (chest tube placement) – is required if there is empyema, hemothorax and pneumothorax. It is also useful for injecting medications into pleural space whenever needed (antibiotics, sclerosing agents, thrombolytics).
3) Pleuro peritoneal shunt – is required in chylous pleural effusion to prevent decreased immunity and malnutrition.
See also our section on pericardial mesothelioma.