To investigate how diabetes mellitus (DM) and the use of metformin affect aneurysm sac changes after endovascular aneurysm repair (EVAR). We conducted a retrospective analysis at a single center of a consecutive series of patients who underwent elective EVAR for infrarenal abdominal aortic aneurysm (AAA) from January 2011 through December 2021. Inter-group comparisons were performed, Kaplan–Meier survival curves were generated for both overall survival and freedom from reintervention, and Cox regression was utilized to detect factors predicting sac shrinkage. The study population consisted of 529 patients, of whom 74 (14.0%) had DM treated with metformin, 26 (4.9%) had DM but did not receive metformin, and 429 (81.1%) had no diabetes. One year after the procedure, patients with diabetes exhibited significantly lower rates of sac shrinkage than those without diabetes (40.0% vs. 52.0%; P = 0.038) and showed a trend toward more frequent stable sac size (52% vs. 42%; P = 0.055). At the latest available follow-up, sac shrinkage was notably lower in the metformin-treated diabetic subgroup compared with non-diabetic patients (48.6% vs. 59.9%; P = 0.047). Sac shrinkage rates did not differ between diabetic patients who were or were not taking metformin. Endoleaks occurred significantly more often in cases with stable sacs or sac expansion. During the nine-year observation period, overall survival was considerably worse in diabetic patients than in non-diabetics (23.5% vs. 37.5%; P < 0.001). This analysis indicates that both diabetes mellitus and metformin therapy are associated with reduced aneurysm sac shrinkage following EVAR. Any endoleak correlated with poorer sac regression at the one-year mark and at final follow-up. Long-term overall survival was significantly inferior among patients with diabetes compared with those without diabetes.
