Hepatic hydrothorax in the absence of ascites - Report of two cases and review of the mechanism

Hepatic hydrothorax is defined as the presence of significant pleural effusion in a cirrhotic patient without primary pulmonary or cardiac disease. The most likely explanation for hepatic hydrothorax appears to be that ascitic fiuid passes through congenital or acquired fenestrations in the diaphragm directly into the pleural space. Congenital predispositions might play a role in this pathogenesis and explain the rarity of pleural effusions in cirrhosis. The description of hepatic hydrothorax in the absence of ascites is very rare. Two cases are described, and previous cases are reviewed in order to delineate the pathogenetic mechanisms of this interesting entity. The differentiation of hepatic hydrothorax without ascites depends on the realization of pressure gradients and occasional complicated flow rate patterns between the peritoneal and pleural cavities. It is concluded that rapid and continuous transdiaphragmatic migration of fluid into the pleural space through persistent defects that are large enough may result in the formation of hepatic hydrothorax without ascites as long as the rate of ascites formation does not exceed the volume capacity of the pleural space(s).