Fever of Unknown Origin — infected Fistula-in-Ano as the focus on 18F-FDG PET-CT

Fever of Unknown Origin (FUO) is a vexing clinical problem. Diagnosis of aetiology is essential for definitive management. A wide array of infective, inflammatory, malignant and miscellaneous pathologies can cause FUO. Hybrid imaging with 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) is now an integral part of FUO management because of its ability to demonstrate the cause in a large proportion of cases. The authors present the case of a 42-year-old male, where an infected fistula-in-ano was detected as the cause of FUO on 18F-FDG PET-CT.