Venous thromboembolism in patients with inflammatory bowel diseases: a case-control study of risk factors

Inflammatory bowel disease (IBD) is a well-known risk factor for venous thromboembolism (VTE). Existing guidelines for thromboprophylaxis in hospitalized patients do not extend to other clinical scenarios that may also be associated with VTE risk. Our aim was to estimate the fraction of VTE events in patients with IBD that could be prevented.A retrospective analysis assessed all patients with IBD diagnosed with VTE at a single academic medical center from 2002 to 2012. Confirmed cases were analyzed for VTE risk factors, inpatient status, the use of deep venous thrombosis prophylaxis, and when applicable the reason for omission of prophylaxis. IBD VTE cases were compared with age- and sex-matched non-IBD VTE controls with regards to risk factors and potential opportunities for VTE prevention.There were 204 patients with IBD (108 ulcerative colitis, 96 Crohn's disease) diagnosed with VTE (110 deep venous thrombosis, 66 pulmonary embolism, 27 intra-abdominal thromboses, and 1 other). One-third of the VTE events occurred in hospitalized patients. Two-third of the medical inpatients and 44% of surgical inpatients who developed VTE did not receive prophylaxis. Importantly, 129 VTE events occurred in outpatients. The proportion of outpatients hospitalized within 4 weeks of developing venous thrombosis was higher in patients with IBD than non-IBD controls (33% versus 15%, P = 0.0003). One-third (36%) of patients were experiencing ambulatory disease flares at the time of VTE diagnosis.A substantial portion of VTE events in patients with IBD occurred in clinical scenarios is not routinely recommended for thromboprophylaxis. Further investigation of primary prophylaxis for patients with IBD in high-risk outpatients may be warranted.