Benign Pleural Effusion
Richard Lazzaro
Joseph LoCicero III
One of the more common chest problems in terms of diagnosis and effective management is the benign pleural effusion. The differential list is long and therapy, in general, relies on effective management of the underlying cause. Table 60-1 lists the wide variety of benign pleural effusions dividing them into transudative and exudative effusions. Light’s criteria help to distinguish transudative from exudative pleural effusions (Table 60-2).
If one or more of Light’s criteria are met, the patient has an exudative effusion. Evaluation of Light’s criteria demonstrates 97.5% sensitivity and 80% specificity for identifying pleural exudates.2
Transudative effusions occur because of increased hydrostatic pressure or decreased oncotic pressures and usually occur as a result of congestive heart failure, nephrotic syndrome, or peritoneal dialysis. In the absence of these benign causes, transudative effusions can also develop in patients with lung cancer secondary to early atelectasis or early lymphatic obstruction. Benign exudative effusions most commonly occur as a complication of pneumonia, pulmonary embolus, and post–coronary artery bypass.
Benign Transudative Effusions
Congestive Heart Failure
Congestive heart failure (CHF) is the most common cause of pleural effusions. Symptoms (i.e., shortness of breath, fatigue, orthopnea, paroxysmal nocturnal dyspnea), physical signs (edema, pulmonary rales, gallop rhythm, displaced left ventricular apical impulse), as well as clinical findings such as cardiomegaly on chest x-ray support a diagnosis of CHF. Effusions are bilateral and symmetric and they respond to diuretics. Intrafissural fluid collection that disappears with diuresis establishes the diagnosis of a pseudotumor. Thoracentesis is reserved for patients with asymmetric effusions, febrile illness, pleuritic chest pain, or persistent symptomatic effusions despite diuretic therapy.
Hepatic Hydrothorax
Pleural effusions occur in approximately 5% of patients with cirrhosis and ascites. Transdiaphragmatic egress of ascitic fluid through diaphragmatic defects is the most likely cause. Hypo- albuminemia, azygos vein hypertension, and thoracic duct leak may also contribute.5 In the absence of cardiopulmonary disease, cirrhotic patients who develop large (>500 mL) pleural effusions, usually right-sided, are diagnosed with hepatic hydrothorax. Sodium restriction and diuretic therapy remain cornerstones of treatment. Since liver transplantation provides definitive treatment, patients should be evaluated for candidacy. Thoracentesis, transjugular intrahepatic portosystemic shunt (TIPS), thoracoscopic closure of diaphragmatic defects, and pleurodesis can be utilized as bridges to transplantation. TIPS is successful in over 75% of cases but can worsen encephalopathy.3,5 Tube thoracostomy is associated with significant fluid shifts with progressive hepatic dysfunction and a high mortality rate and is therefore discouraged.
Nephrotic Syndrome
Nephrotic syndrome is characterized by massive proteinuria with resultant hypoproteinemia leading to edema. A complex interaction of the resultant decrease in oncotic pressure along with increased activity of aldosterone and vasopressin and decreased atrial natriuretic hormone as well as other cytokines leads to edema. Pleural effusions can be seen in up to 20% of patients. Nephrotic syndrome leads to a hypercoagulable state with renal vein thrombosis and pulmonary embolus. Treatment of the nephrotic syndrome results in an increase in serum protein levels and usually resolution of the effusions.13,14
Fontan Procedure
Vena caval to pulmonary arterial shunting results in obligatory venous hypertension, elevated mean capillary pressure, and pleural effusion.
Superior Vena Cava Obstruction
Superior vena caval obstruction secondary to trauma, iatrogenic causes (indwelling catheter, electrode, venous access), and benign fibrosing mediastinitis is associated with elevated mean capillary pressure and pleural effusion.
Urinothorax
Retroperitoneal urine leak as a result of urinary tract trauma or obstruction can lead to the development of a pleural effusion.
Patients have an elevated ratio of pleural to serum creatinine. Treatment requires management of the urinary tract obstruction or trauma as well as pleural drainage.
Patients have an elevated ratio of pleural to serum creatinine. Treatment requires management of the urinary tract obstruction or trauma as well as pleural drainage.
Table 60-1 Differential Diagnoses of Benign Pleural Effusions | ||
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