Use of (18)F-FDG PET/CT to locate primary malignancies in patients with hepatic cirrhosis and malignant ascites.

Objective: Ascites in patients with hepatic cirrhosis is caused by cirrhosis in most cases. For most malignant ascites, the primary malignancy could be readily identified using conventional imaging methods, e.g., computed tomography (CT) and magnetic resonance imaging (MRI). However, in a small fraction of the patients, the primary malignancy remains occult even with these examinations. In this retrospective study, we assessed the usefulness of (18)F-FDG PET/CT in patients with hepatic cirrhosis and malignant ascites of otherwise unknown origin.

Methods: Twenty-eight patients with malignant ascites of unknown primary sites after CT, MRI and ultrasound during the period of five years between January 2008 and December 2012 had received (18)F-FDG PET/CT. Medical records of these patients were reviewed and analyzed.

Results: Elevated (18)F-FDG absorption was found in 23 of 28 cases in the following sites: gastrointestinal tract (n=10, 43.5%), prostate (n=5, 21.7%), peritoneum (n=4, 13.3%), and ovary (n=4, 13.3%). Cancer was confirmed by pathology in 20 cases after open or laparoscopic surgeries. Five patients were found to have benign ascites, among which, 3 were found to be false positive due to tuberculosis. SUV values were significantly higher for tumors than for benign lesions (mean values, 6.95 vs. 2.94; P=0.005).

Conclusions: The (18)F-FDG PET/CT can be as a powerful imaging tool in identifying tissue origin in liver cirrhosis patients suspected of cancers or with cancers of unknown primary sites.