Value of 18F-FDG PET/CT in differentiating the character of ascites

Abstract

Objective To assess the value of PET/CT in differentiating the character of ascites in patients with ascites of undetermined origin.Methods A total of 70 patients with ascites of undetermined origin were analyzed retrospectively.Each patient underwent a whole body 18F-FDG PET/CT scan,serum tumor marker examination and cytological examination of ascites.The diagnosis of peritoneal carcinomatosis was established based on the results of histopathology examination,multimodality imaging and clinical follow-up after more than 6 months.T-test,McNemar test and Kappa test were used to analyze the data.Results Forty-eight patients were proven to have malignant ascites caused by peritoneal carcinomatosis according to histopathology examination,and the rest were proven to have benign ascites.The SUVmax of peritoneal lesions in the malignant ascites group and benign ascites group were 6.08 ± 3.92 and 2.66 ± 1.74,respectively (t =-5.063,P ＜ 0.001 ).PET/CT lead to accurate diagnosis in 43 patients with malignant ascites and in 20 patients with benign ascites.False-positive and false-negative results were found in 2 and 5 patients,respectively.The sensitivity,specificity and accuracy of PET/CT for diagnosing peritoneal carcinomatosis were 89.6％ (43/48),90.9％ (20/22) and 90.0％ (63/70),respectively.Located CT analysis accurately diagnosed 23 patients with malignant ascites and 18 patients with benign ascites.False-positive and false-negative diagnosis occurred in 4 and 25 patients,respectively.The sensitivity,specificity and accuracy of located CT for diagnosing peritoneal carcinomatosis were 47.9％ (23/48),81.8％ ( 18/22 ) and 58.6％ (41/70),respectively.The diagnostic sensitivities between PET/CT and located CT were significantly different (x2 =14.286,P ＜0.001 ).The cytological examination results were positive in 21 patients with malignant ascites.The diagnostic sensitivity,specificity and accuracy of cytological examination were 43.8％ (21/48),100％ (22/22) and 61.4％ (43/70),respectively.The diagnostic sensitivity of PET/CT was higher than that of cytological examination (x2 =13.885,P ＜0.001 ).There was good agreement between the diagnosis using PET/CT and the final diagnosis (Kappa =0.776,P ＜ 0.001 ).However,the agreements between the diagnosis using located CT or cytological examination and the final diagnosis were poor ( Kappa =0.236 and 0.328,both P ＜ 0.05 ).Conclusion 18F-FDG PET/CT may help in diagnosing peritoneal carcinomatosis in patients with ascites of undetermined origin,and it can be used to differentiate the character of ascites. Key words: Ascites; Neoplasm metastasis ; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose