Increased F-18 FDG intestinal uptake in diabetic patients on metformin: a matched case-control analysis

A matched case-control study was performed to assess the relationship between metformin use and the degree of F-18 fluorodeoxyglucose (FDG) bowel activity in diabetic patients.

Seventy-seven diabetic patients referred to our department for a positron emission tomography/computed tomography study, including 45 on metformin, were compared with nondiabetic controls matched for sex, age, and body mass index. Positron emission tomography studies were obtained in a standard manner and reviewed in a blinded fashion. F-18 FDG uptake in the GI tract was evaluated quantitatively using maximal standardized uptake values and visually using a previously published semiquantitative scale.

F-18 FDG uptake in small and large bowel was significantly increased in metformin patients compared with nondiabetic controls both visually and quantitatively (all P < 0.0001), as well as compared with nonmetformin patients with diabetes. Control sites (liver, fat, muscle) showed similar uptake. Multiple regression analysis confirmed that metformin was the variable most strongly associated with bowel uptake.

Physiologic accumulation of F-18 FDG in bowel is increased in diabetic patients maintained on metformin.