Metformin discontinuation for 48 hours reduces intestinal fluorodeoxyglucose uptake in 18F-fluorodeoxyglucose positron emission tomography/computed tomography

Abstract

Objective: To evaluate the effect of 48-hour metformin discontinuation on bowel fluorodeoxyglucose (FDG) uptake in a Chinese population undergoing 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) imaging. Methods: All patients with known type 2 diabetes mellitus treated with metformin who had had a previous FDG PET/CT examination performed in our centre, and who were scheduled for a second FDG PET/CT examination within 1 year of the first one, were recruited. These subjects were advised to stop metformin for 48 hours prior to the second examination. The intestinal uptakes were graded visually by a four-point scale and semiquantitatively by maximum standardised uptake value (SUVmax) of small and large bowel segments. Any differences in intestinal uptake, as well as other differences in examination day blood glucose levels between the two successive examinations were compared. Results: In total, 44 patients were included. Metformin discontinuation resulted in a significant reduction in small and large bowel uptake by visual scoring. The SUVmax values were significantly lower in all bowel segments except duodenum. Examination day blood glucose levels after 48-hour metformin discontinuation were <11 mmol/L, in all examinations. Conclusion: Metformin discontinuation for 48 hours prior to scanning significantly reduced intestinal uptake and should be considered as a method to improve PET/CT interpretation.