Metformin-Induced Intense Bowel Uptake Observed on Restaging FDG PET/CT Study in a Patient with Gastric Lymphoma

UNLABELLED A 53-year-old man with a diagnosis of gastric non-Hodgkin lymphoma (NHL) underwent PET/CT scans both prior to starting chemotherapy and immediately following completion of chemotherapy to evaluate the response to therapy. Pre-therapy PET/CT images showed intense FDG uptake in the antral region of the stomach. Biodistribution of FDG was otherwise unremarkable. The patient was started on metformin in the middle of his therapy period to provide glycemic control. Post-therapy PET/CT study performed after 6 courses of chemotherapy showed complete resolution of the disease with no evidence of residual FDG uptake. However, intense and diffuse FDG accumulation is observed in the bowel, which was interpreted as physiological and most probably due to metformin administration. It should be borne in mind that there are a number of physiological variants of FDG biodistribution seen on PET/CT imaging. Recognizing physiologic bowel activity is crucial for the accuracy of PET image interpretation. CONFLICT OF INTEREST None declared.