Hepatic hydrothorax refers to the presence of a pleural effusion (usually >500 mL) in a patient with cirrhosis who does not have other reasons to have a pleural effusion (eg, cardiac, pulmonary, or pleural disease) [1,2]. Hepatic hydrothorax occurs in approximately 5 to 10 percent of patients with cirrhosis. In a retrospective analysis of 495 patients with cirrhosis and pleural effusion, 16 percent had hepatic hydrothorax . While patients with ascites can often tolerate up to 5 to 10 L of fluid with only mild symptoms, those with a pleural effusion can have severe symptoms (such as shortness of breath, cough, and hypoxemia) with as little as 500 mL of fluid.
This topic will review the clinical manifestations, diagnosis, and management of hepatic hydrothorax. Other complications of cirrhosis, including ascites and variceal hemorrhage, are discussed elsewhere. (See "Cirrhosis in adults: Overview of complications, general management, and prognosis" and "Ascites in adults with cirrhosis: Initial therapy" and "Ascites in adults with cirrhosis: Diuretic-resistant ascites" and "Primary and pre-primary prophylaxis against variceal hemorrhage in patients with cirrhosis" and "Prevention of recurrent variceal hemorrhage in patients with cirrhosis".)
Although the exact mechanisms involved in the development of hepatic hydrothorax are incompletely understood, it probably results from the passage of ascites from the peritoneal cavity into the pleural cavity through small diaphragmatic defects. These defects are typically less than 1 cm (and may be microscopic) and are generally located in the tendinous portion of the diaphragm [4-9]. Hepatic hydrothorax becomes apparent when the absorptive capacity of the pleural space is exceeded. The pathologic mechanisms behind the formation of ascites are discussed in detail elsewhere. (See "Pathogenesis of ascites in patients with cirrhosis".)
The diaphragmatic defects are more often found in the right hemidiaphragm, likely due in part to the fact that the left hemidiaphragm is thicker and more muscular. Hepatic hydrothorax develops on the right side in approximately 73 to 85 percent of patients, on the left side in approximately 13 to 17 percent, and bilaterally in approximately 2 to 10 percent [3,10,11].
The negative intrathoracic pressure generated during inspiration promotes the passage of fluid from the abdominal cavity to the pleural space. This could explain why some patients with hepatic hydrothorax do not have apparent ascites [12-14]. This theory is supported by studies using 99mTc-human albumin or 99mTc-sulphur colloid, which demonstrate unidirectional passage of these markers from the abdominal cavity to the pleural cavity [12,15-19].