Lesser sac fluid in predicting the etiology of ascites: CT findings.

The CT scan of 100 patients with ascites were reviewed to assess the relative distribution of fluid in the greater and lesser peritoneal sacs. Discordant fluid accumulations were found in most cases. Patients with benign, transudative ascites (e.g., peritoneal dialysis, cirrhosis, congestive heart failure) had large greater sac collections with little fluid in the lesser sac. Those patients with diseases of organs bordering the lesser sac (e.g., pancreatitis, posteriorly penetrating gastric ulcer) had larger lesser sac fluid collections with little in the greater sac. Cytologically positive carcinomatosis of the abdomen was associated with concordant fluid volumes in these two spaces. These findings suggest that fluid within the lesser sac is not a typical manifestation of generalized peritoneal ascites and that its presence should direct a search for pathology in neighboring organs and for peritoneal malignancy.