Metformin-related diffuse FDG uptake in the bowel

Case contributed by Dr Justin G Peacock

Presentation

Patient receiving initial PET/CT for recent cancer diagnosis.

Patient Data

Age: 60 years
Gender: Female

18F-FDG PET/CT demonstrates diffuse uptake throughout the colon and distal small bowel. There are no bowel wall thickening or inflammation throughout the FDG-avid bowel. There is intense FDG uptake in the right cervix extending caudally to the right vaginal fornix.

Case Discussion

Intense FDG uptake throughout the bowel can be seen in the context of metformin use, as in this case. Metformin use increases glucose excretion from the bowel, thereby increasing FDG excretion in the bowel. Correlation with the patient's medications and the CT findings should be made in such cases. If the medication history is unknown, the CT should be assessed for signs of diffuse infectious or inflammatory colitis, including bowel wall thickening and pericolic fat stranding.

In this case, the patient has a history of cervical cancer with intense FDG uptake and spread to the right upper vagina. The intense bowel uptake is consistent with the patient's known metformin use. The bowel is decompressed without wall thickening and inflammation.

Researchers have found that discontinuation of metformin 48 hours before the PET/CT can reduce FDG excretion into the bowel. The discontinuation is strongly recommended in cases of bowel malignancy.

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