Inflammatory Bowel Disease Increases the Risk of Venous Thromboembolism in Children: A Population-Based Matched Cohort Study

Abstract Background and Aims Although venous thromboembolism [VTE] is a well-known complication of inflammatory bowel disease [IBD] in adults, limited data exist on the risk in children. We report the incidence of VTE among children with and without IBD. Methods We conducted a matched cohort study within a distributed network of population-based Canadian provincial health administrative databases. Children <16 years diagnosed with IBD were identified using validated algorithms from administrative data in Alberta, Manitoba, Nova Scotia, Ontario and Québec and compared to age- and sex-matched children without IBD. Hospitalizations for VTE within 5 years of IBD diagnosis were identified. Generalized linear mixed-effects models were used to pool province-specific incidence rates and incidence rate ratios [IRR] with 95% confidence intervals [CI]. Hazard ratios [HR] from Cox proportional hazards models were pooled with fixed-effects meta-analysis. Results The 5-year incidence of VTE among 3593 children with IBD was 31.2 [95% CI 23.7–41.0] per 10 000 person-years [PY] compared to 0.8 [95% CI 0.4–1.7] per 10 000 PY among 16 289 children without IBD [unadjusted IRR 38.84, 95% CI 16.59–90.83; adjusted HR 22.91, 95% CI 11.50–45.63]. VTE was less common in Crohn’s disease than ulcerative colitis [unadjusted IRR 0.47, 95% CI 0.27–0.83; adjusted HR 0.52, 95% CI 0.29–0.94]. The findings were similar for deep vein thrombosis and pulmonary embolism when comparing children with and without IBD. Conclusions The risk of VTE is much higher in children with IBD than controls without IBD. While the absolute risk is low, we found a higher incidence rate than previously described in the pediatric literature. Conference Presentation: An abstract based on the data included in this paper was presented at Canadian Digestive Diseases Week [Montréal, Canada] in March 2020.