Incidental anal (18)fluorodeoxyglucose uptake: Should we further examine the patient?

BACKGROUND: There are no studies on incidental anal (18)F-fluorodeoxyglucose ((18)FDG) uptake. AIM: To assess the rate and aetiologies of incidental anal (18)FDG uptake and to evaluate the correlation between (18)FDG positron-emission tomography/computed tomography (PET/CT) parameters and the diagnosis of an anorectal disease. METHODS: The data from patients with incidental anal (18)FDG uptake were retrospectively analysed. Patients who underwent anorectal examinations were identified and compared to those who did not undergo examinations. Patients who were offered treatment were then identified and compared to those who did not receive treatment. RESULTS: Among the 43020 (18)FDG PET/CT scans performed, 197 (18)FDG PET/CT scans of 146 patients (0.45%) reported incidental anal uptake. Among the 134 patients included, 48 (35.8%) patients underwent anorectal examinations, and anorectal diseases were diagnosed in 33 (69.0%) of these patients and treated in 18/48 (37.5%) patients. Among the examined patients, those with a pathology requiring treatment had significantly smaller metabolic volumes (MV) 30 and MV41 values and higher maximal and mean standardized uptake value measurements than those who did not require treatment. CONCLUSION: Incidental anal (18)FDG uptake is rare, but a reliable anorectal diagnosis is commonly obtained when an anorectal examination is performed. The diagnosis of an anorectal disease induces treatment in more than one-third of the patients. These data should encourage practitioners to explore incidental anal (18)FDG uptake systematically.