The role of standardized uptake value in ¹⁸F-FDG PET/CT for auxiliary diagnosis of ascites with unknown cause

Objective: To explore the value of SUV in patients with ascites of unknown cause. Methods: A total of 55 patients (24 males, 31 females, average age 54.8 years, age range: 23-82 years) with ascites of unknown cause who underwent ¹⁸F-FDG PET/CT scan were retrospectively enrolled in this study. SUV_max and SUV_mean of ascites and liver were measured and their ratios (T/NT) were calculated and compared by two-sample t test. All patients were followed up and had final diagnoses. Sensitivity, specificity, accuracy, positive predictive value and negative predictive value were calculated respectively. The diagnostic efficiency was compared among ¹⁸F-FDG PET/CT tumor localization alone,ascites radioactivity and ascites cytology examination by χ² test or Fisher exact test. Results: Besides the high metabolized primary lesions and/or metastasis, the liver and spleen swamped by ascites with high radioactivity were visualized on MIP images. The SUV_max and SUV_mean of malignant ascites were 1.78±0.65 and 1.37±0.38 respectively, which were higher than those of benign ascites (1.11±0.36 and 0.72±0.22; t=4.13, 6.82, both P<0.05). T/NT of malignant ascites was higher than that of benign ascites (SUV_max: 0.64±0.20 vs 0.48±0.12, t=3.27, SUV_mean: 0.68±0.17 vs 0.38±0.10, t=7.21; both P<0.05). The diagnostic sensitivity, specificity and accuracy of SUV in ascites were 75.0% (27/36), 94.7% (18/19) and 81.8% (45/55), respectively. The sensitivity and accuracy of SUV were higher than those of cytological examination (44.4% (16/36) and 63.6% (35/55); χ²=6.98, 4.58, both P<0.05). The specificity of SUV was higher than that of tumor localization by ¹⁸F-FDG PET/CT (63.2%, 12/19; χ²=5.70, P<0.05). Conclusion: Significantly higher SUV_max and SUV_mean in malignant ascites than benign ascites were noted, which might play an adjuvant role in patients with ascites of unknown cause. (authors)