Diuresis makes vesicocolic fistula visible on FDG PET/CT.

A 71-year-old man with rectal cancer history was referred for FDG PET/CT due to serum carcinoembryonic antigen level elevation. In addition to rectal cancer recurrent lesion, the FDG PET/CT scan also showed homogeneous intense FDG accumulation in the whole segment of descending colon and a small air bubble in the urinary bladder. After furosemide injection, the vesicocolic fistula was confirmed by typical air pattern in the urinary bladder on attenuation CT images and the decrease FDG activity in the descending colon. The patient has had the clinical manifestations of pneumaturia and watery diarrhea which support the diagnosis of vesicocolic fistula.