Investigation of pleural fluid
Whenever there is doubt about the cause of an effusion,aspiration should be performed. Loculated or small effusionsare best aspirated with ultrasound localization.Bloodstained effusions, rather than the frank blood of ahaemothorax, are most common with malignancy, but alsooccur in pulmonary infarction and following chest trauma.
Rare causes of a bloody effusion include cirrhosis, tuberculosisand leukaemia. Infected pleural fluid is turbid, andwith advanced empyema becomes purulent. With a chylouseffusion the fluid is a milky white colour.Analysis of pleural fluid protein concentration broadlyseparates transudates (less than 3g/dL) from exudates(more than 3g/dL), but in a large number of cases borderline,unhelpful values are obtained.
Cytology is a key investigation, not simply for malignantcells. The presence of numerous polymorphonuclearleukocytes suggests bacterial infection; lymphocytespredominate in tuberculosis but are also common in anychronic effusion; eosinophils are numerous in the effusionsof pulmonary eosinophilia, polyarteritis nodosa andHodgkin's disease. Eosinophils can be the prominent cellsfollowing pulmonary infarction, and may also accumulatefollowing bleeding into the pleural space from any cause.
Pneumonias and rheumatoid arthritis are less usual causesfor an eosinophilic effusion. Malignant cells are identifiedin up to half of patients with tumour involving the pleura.Bacteria may be demonstrated in postpneumonic effusions,particularly in those progressing to empyema. In tuberculosisacid-fast bacilli are only occasionally identified, butculture of pleural fluid for the mycobacteria is often useful.
In rheumatoid arthritis the pleural fluid contains acharacteristically very low concentration of glucose.When pleural aspiration is not diagnostic pleural biopsyshould be performed. Biopsy is particularly helpful inmalignant disease of the pleura and in tuberculosis.
About the Author
Dr Izharul Hasan
drizharnium@gmail.com, Bangalore India Hi Friends, I am Izhar currently pursuing MD in Unani System of Medicine from NIUM Bangalore, love... (show bio)
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