18F-FDG PET/CT in Urachal Abscess.

We report interesting images of a pelvic mass in an 11-year-old girl. She presented with fever, chronic fatigue, and weight loss without abdominal pain. Abdominal ultrasound, contrast-enhanced CT, and F-FDG PET/CT were equivocal. F-FDG PET/CT revealed an irregular, intense FDG-avid pelvic mass in close contact with the bladder. Both infectious and malignancy complications were suspected, but pathological examination confirmed a urachal abscess. As most of the urachal carcinomas are mucinous adenocarcinomas with low or non-FDG uptake, intense uptake might indicate an abscess rather than a carcinoma.