Quality control program to manage metformin stimulated 18-FDG bowel uptake in PET/CT imaging.

Learning Objectives 1. Review the effect of metformin in the GI tract. 2. Illustrate how metformin induced 18-FDG bowel uptake affects the quality of PET/CT imaging and its interpretation. 3. Describe a quick and simple scheme to monitor bowel uptake useful for a quality improvement program. 4. Illustrate the use of the monitoring scheme within a quality improvement program designed to address the problem of metformin induced bowel activity in 18-FDG PET/CT imaging.

Objective: Metformin is an oral hypoglycemic used in the treatment of type 2 diabetes. Use of metformin is associated with increased uptake of 18-FDG in the colon, and to a lesser extent the small bowel. This bowel uptake can be striking, and can mimic malignancies. Hence, it is desirable to manage the degree of bowel uptake in clinical 18-FDG PET/CT through a quality control program. Methods: To do this we developed a program to identify patients taking metformin, stop the medication for 48 hours before injection of 18-FDG, monitor compliance with instructions, and document the expected reductions in bowel uptake by means of a quick but quantitative scheme. We also monitored for hyperglycemia. This educational exhibit provides details of the program and suggestions for its implementation. Results: In our baseline measurements 59% of diabetics were taking metformin, and 86% of these had taken the medication within 24 hours of injection of 18-FDG. Their bowel SUVmax averaged 6.8 gm/ml while diabetics not on metformin had average bowel SUVmax of 3.7 gm/ml. After implementation of the quality control program, 56% of diabetics were on metformin. Sixty-seven percent (67%) stopped taking the medication for at least 48 hours before injection of 18-FDG, and their average SUVmax dropped to 3.6 gm/ml. There were no episodes of significant hyperglycemia. Conclusion: The quality control program reduces 18-FDG bowel uptake in diabetics taking metformin, but compliance with instructions needs improvement.