The Role of 18F-FDG PET/CT in the Evaluation of Ascites of Undetermined Origin

Unlabelled: The first aim of our study was to compare the role of (18)F-FDG PET/CT with that of CT alone in detecting the primary cause of ascites. A secondary aim was to compare the value of (18)F-FDG PET/CT with that of CT alone in detecting abdominal cavity metastasis. Finally, we analyzed the receiver-operating-characteristic (ROC) curves of maximal standardized uptake values (SUVmax), serum carcinoembryonic antigen, CA19-9, and CA12-5 for differential diagnostic abilities.

Methods: The (18)F-FDG PET/CT scans of 40 patients with ascites of undetermined origin, including 30 patients with malignant diseases and 10 with benign lesions, were reviewed for the presence of ascites. Among the 40 patients, 34 had received their diagnosis by pathologic examination and 6 by clinical follow-up. We also assessed the (18)F-FDG PET/CT scans of 20 healthy volunteers for comparison. All (18)F-FDG PET/CT images were visually interpreted, and the SUVmax was measured. We compared the mean diameter of true-positive lesions with that of false-negative lesions. The diagnostic abilities of SUVmax, serum carcinoembryonic antigen, CA19-9, and CA12-5 were compared using the ROC curve.

Results: The sensitivity, specificity, and accuracy of PET/CT in detecting the primary cause of ascites were 63.3% (19/30), 70.0% (7/10), and 65.0% (26/40), respectively, and those of CT alone were 36.7% (11/30), 80% (8/10), and 47.5% (19/40), respectively (sensitivity, P < 0.05). The sensitivity of PET/CT was higher than that of CT alone for detecting abdominal cavity metastasis (86.4% vs. 27.3%, P < 0.01). The SUVmax in patients with malignant primary and metastatic lesions was significantly higher than that in healthy volunteers and in patients with benign ascites (P < 0.05). The mean maximal diameter of false-negative lesions was significantly smaller than that of true-positive lesions (P < 0.05). In ROC analysis, the areas under the curve of SUVmax, serum carcinoembryonic antigen, CA19-9, and CA12-5 were 0.803 (P < 0.01), 0.773 (P < 0.05), 0.552 (P > 0.05), and 0.220 (P < 0.01), respectively.

Conclusion: (18)F-FDG PET/CT assisted in detecting the original cause of ascites. The differential diagnostic ability of (18)F-FDG PET/CT was superior to that of CT alone, tumor markers, and cytology. More attention should be paid to peritoneal tuberculosis, which can markedly accumulate (18)F-FDG and mimic peritoneal carcinoma.