The efficacy of whole-body FDG-PET or PET/CT for autoimmune pancreatitis and associated extrapancreatic autoimmune lesions

Purpose The aim of this study was to evaluate retrospectively the efficacy of whole-body ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) for autoimmune pancreatitis (AIP) and associated extrapancreatic autoimmune lesions. Methods Whole-body FDG-PET or PET/computed tomography (CT) findings were reviewed in six patients with AIP. The initial PET scans were performed 1 h and 2 h after FDG injection in all six patients. Follow-up PET scans were performed during or following steroid therapy in five patients and in one patient who did not have steroid therapy. Results The initial PET scans revealed intense FDG uptake by AIP in all six patients. The maximum standardized uptake value (SUVmax) increased in four patients and was stable in two patients. The intense uptake in the pancreas disappeared during or following steroid therapy in five patients and in one patient who showed spontaneous remission of AIP. Abnormal FDG uptake by extrapancreatic autoimmune diseases was observed in five of the six patients: sclerosing sialadenitis (n = 5), lymphadenopathy (n = 5), retroperitoneal fibrosis (n = 2), interstitial nephritis (n = 2) and sclerosing cholecystitis (n = 1). Abnormal FDG uptake disappeared in the salivary glands (n = 4), lymph nodes (n = 4), retroperitoneum (n = 2), kidneys (n = 1) and gallbladder (n = 1) during or following steroid therapy and remained in the salivary glands and lymph nodes of a spontaneous remission patient. Conclusion These results suggest that whole-body FDG-PET may be useful for detecting AIP and associated extrapancreatic autoimmune lesions and for monitoring their disease activity but that dual time point imaging may not be useful for differentiating malignancy from AIP.