Risk of Venous Thromboembolism After Colorectal Cancer Surgery in Patients With and Without Inflammatory Bowel Disease.

Introduction: Inflammatory bowel disease (IBD) is associated with elevated postoperative mortality in patients undergoing colorectal cancer (CRC) surgery. Venous thromboembolism (VTE) may partially contribute to this elevated mortality. We investigated VTE risk in patients with and without IBD undergoing their first CRC surgery.

Methods: We conducted a population-based cohort study using Danish health registries (1996-2021), including all patients undergoing first-time CRC surgery (n = 83,950). Patients with a prior IBD diagnosis were defined as exposed. We calculated the 365-day cumulative risks of VTE and used Cox regression to compute adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs).

Results: The 30-day VTE risk was 1.5% in patients with IBD and 0.7% in those without IBD (aHR 1.61; 95% CI 0.86-3.01). During this period, the strongest associations were observed among male patients (aHR 2.26; 95% CI 1.06-4.82), patients aged 60-69 years (aHR 4.63; 95% CI 1.88-11.39), those who had received IBD treatment before surgery (aHR 1.95; 95% CI 0.97-3.95), and patients with active disease (aHR 5.29; 95% CI 1.69-16.56). These associations were primarily driven by patients with ulcerative colitis. HRs remained elevated during 91-365 days.

Discussion: Patients with IBD are at elevated risk of VTE after CRC surgery compared with those without IBD. The strongest associations were observed in those who had received IBD treatment before surgery and in those with active disease, particularly patients with ulcerative colitis. These findings emphasize the need for increased VTE awareness and optimizing disease control in patients with high-risk IBD.