CT of ascites: differential diagnosis.

Forty-three patients with ascites were evaluated with computed tomography (CT). Neoplasm accounted for 72% of the cases; the remainder included inflammatory processes (10%), cirrhosis (8%), trauma (2%), renal transplant (2%), congestive heart failure (2%), and unknown (4%). An accuracy of 93% was achieved in correctly predicting the presence of ascites alone or together with a mass. The potential for diagnostic error when mass lesions coexist with ascites is discussed and parameters are described to help avoid such errors. These include: (1) knowledge of the normal anatomy of the fluid-filled intraperitoneal space and fluid flow patterns; (2) inspection of the intra-/extraperitoneal interface; and (3) evaluation of the bowel-mesentery pattern.