Intravenous Contrast in Patients With Diabetes on Metformin

New Common Sense Guidelines

Arti D. Shah, MD; Cody McHargue, BA; Judy Yee, MD; Robert J. Rushakoff, MD

Disclosures

Endocr Pract. 2016;22(4):502-505. 

In This Article

Exceptions

We believe there remain some possible exceptions to the new guidelines. Metformin leads to intense, diffusely increased fluorodeoxyglucose (FDG) uptake in the colon, and to a lesser degree, the small intestine, which limits the diagnostic capabilities of FDG positron emission tomography (PET)/CT scanning and may mask gastrointestinal malignancies.[16] The authors point out that this may leave some intestinal cancers or metastatic bowel lesions undetected, potentially resulting in incorrect cancer staging and inability to detect second primary cancers and assess therapeutic responses. This masking is unrelated to the administration of IV contrast. It is therefore recommended that metformin should be discontinued 48 hours before FDG PET/CT scanning in oncology patients to optimize scan sensitivity for malignancy detection. Unfortunately, as elevated plasma glucose can directly compete for uptake with radiolabeled glucose, there may be decreased sensitivity of the test in patients with elevated glucose (in this case as a result of metformin discontinuation). In this case, patients may require additional antihyperglycemic agents after metformin discontinuation to maintain reasonable glycemic control.[16]

We applaud the new guidelines from the ACR. They reflect the current data that do not show any significant risk of AKI in patients with normal baseline renal function or an eGFR ≥30 mL/min/1.73 m2 who are taking metformin and having an IV contrast procedure; therefore, there is no need to discontinue metformin before or after IV contrast and no obligation to check renal function after the exam. Finally, common sense prevails.

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