Clearance of the high intestinal 18F-FDG uptake associated with metformin after stopping the drug
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This study was done to determine whether interruption of metformin before 18F-FDG PET/CT imaging could prevent the increased 18F-FDG uptake in the intestine caused by this drug.
Included in the study were 41 patients with known type 2 diabetes mellitus who were referred to our department for evaluation of various neoplastic diseases. Patients underwent two 18F-FDG PET/CT scans, the first while they were on metformin and the second after they had stopped metformin. They stopped metformin and did not take any other oral antidiabetic medication starting 3 days before the second study and their blood glucose level was regulated with insulin when necessary to keep it within the range 5.55–8.33 mmol/l. FDG uptake was graded visually according to a four-point scale and semiquantitatively by recording the maximum standardized uptake value (SUVmax) in different bowel segments. A paired-samples t-test method was used to determine whether there was a significant difference between SUVmax measurements and visual analysis scores of the metabolic activity of the bowel in the PET/CT scans before and after stopping metformin.
Diffuse and intense 18F-FDG uptake was observed in bowel segments of patients, and the activity in the colon was significantly decreased both visually and semiquantitatively in PET/CT scans performed after patients stopped metformin (p<0.05). There was a statistically significant decrease in activity in the small intestine on visual analysis (p<0.05), but semiquantitative measurements did not show a significant decrease in the SUVmax values in the duodenum or jejunum (p>0.05).
Metformin causes an increase in 18F-FDG uptake in the bowel and stopping metformin before PET/CT study significantly decreased this unwanted uptake, especially in the colon, facilitating the interpretation of images obtained from the abdomen and preventing the obliteration of lesions.
KeywordsMetformin 18F-FDG PET/CT Antidiabetic Bowel uptake
We express special thanks to Mrs. Funda Sezgin for her help with the statistical analysis.
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