Accumulation of fluid within the peritoneal cavity results in ascites. In the United States, ascites is most often due to portal hypertension resulting from cirrhosis. Other common causes include malignancy and heart failure. Successful treatment of ascites depends upon an accurate diagnosis of its cause (table 1 and table 2 and table 3 and algorithm 1) .
This topic will review the evaluation of adults with ascites. Performance of paracentesis, specific causes of ascites, the initial therapy of ascites in patients with cirrhosis, and the treatment of refractory ascites are discussed in detail separately. (See "Diagnostic and therapeutic abdominal paracentesis" and "Malignancy-related ascites" and "Chylous, bloody, and pancreatic ascites" and "Tuberculous peritonitis" and "Ascites in adults with cirrhosis: Initial therapy" and "Ascites in adults with cirrhosis: Diuretic-resistant ascites".)
In 2013, the American Association for the Study of Liver Diseases (AASLD) updated its guideline on the management of adult patients with ascites due to cirrhosis (table 4) [2,3]. The discussion that follows is generally consistent with that guideline.
There are numerous causes of ascites, but the most common cause of ascites in the United States is cirrhosis, which accounts for approximately 80 percent of cases (table 1) . Up to 19 percent of patients with cirrhosis will have hemorrhagic ascites, which may develop spontaneously (72 percent probably due to bloody lymph and 13 percent due to hepatocellular carcinoma) or following paracentesis . Other common causes of ascites include malignancy-related ascites and ascites due to heart failure.
Ascites can be classified based on the underlying pathophysiology :