What are the indications for performing a thoracentesis?
What steps should be taken to reduce the likelihood of complications?
What diagnostic criteria differentiate the three types of pleural effusions, namely, transudates, exudatives, and empyema?
Physicians or other providers perform an estimated 173,000 thoracenteses in the United States every year. In general, the procedure is usually safe and well tolerated. However, when iatrogenic pneumothorax does occur, chest tube insertion may be required for up to 50% of the patients with an increased average length of stay of approximately four days. This complication not only incurs substantial increase in cost, but also increases morbidity and mortality.
Pleural effusions develop secondarily to systemic changes (transudates) or to local causes (exudates). Systemic causes that lead to the formation and absorption of pleural fluid most commonly include left ventricular heart failure, pulmonary embolism, cirrhosis, and renal disease. Acute pancreatitis may cause a left-sided pleural effusion. Pleural effusions commonly occur after abdominal surgery due to the porous diaphragm and are usually benign. Renal diseases that can cause pleural effusion include the nephrotic syndrome and urinothorax from hydronephrosis. Myxedema and cerebrospinal fluid leak to the pleura are other causes of transudates.
Local causes (exudates) are most commonly bacterial pneumonia, viral infection, malignancy, and pulmonary embolism. Approximately 40% of patients with community-acquired pneumonia will develop pleural effusions, and approximately 10% of these will be complicated parapneumonic effusions or empyema. Parapneumonic effusions start out as sterile, reactive effusions and can rapidly progress to loculated empyema in immunocompromised patients or when there is a delay in administration of appropriate antibiotics. Other infectious causes include viral or fungal disease and tuberculosis. Failure to identify those patients with empyema or significant inflammation necessitating pleural drainage can result in trapped lung. Pancreatic pseudocyst, intraabdominal abscess, post–coronary artery bypass grafting or cardiac contusion, pericardial disease, drug-induced pleuritis, rheumatologic disease, uremia, and gynecologic disorders may also cause exudates.
The most common causes of malignant pleural effusions in descending order of frequency are lung cancer, breast cancer, and lymphoma. In a patient with a prior history of asbestos exposure, mesothelioma should be suspected, especially if the pleural effusion is grossly hemorrhagic. While dullness to percussion and reduced tactile fremitus are valuable findings to help identify a pleural effusion (positive likelihood ratio [LR+], 8.7 and 5.7, respectively)1, the physical examination is usually not helpful in diagnosing the cause of the pleural effusion. If a patient has yellow, dystrophic nails, chronic peripheral edema, and chronic exudative effusions, the yellow nail syndrome should be suspected (Moldonado, and Ryu, 2009).
Thoracentesis is performed for diagnostic or therapeutic purposes. The strict indications for thoracentesis are the presence of pleural fluid of unknown etiology where the physician cannot initiate care prior to diagnosis, and severe dyspnea. The first step is to determine whether there is fluid by radiographic imaging. On chest X-ray (CXR), a pleural effusion will characteristically push the heart to ...