Background: Patients with inflammatory bowel disease (IBD) may be at increased risk of having venous thromboembolism.
Methods: Medical records from 1,253 IBD patients attending hospital care during the years 1987-97 were studied. These patients were recruited from a population of 340,000 inhabitants. Patients with verified venous thrombosis were characterized clinically, and blood samples were examined for coagulopathy including analyses of antithrombin, plasminogen, protein C, protein S, factor V, and prothrombin mutations. As control groups we used 99 patients with verified venous thrombosis and no history of IBD and 288 volunteers with no history of thrombosis.
Results: The incidence of venous thrombosis was 1.5/1,000 IBD patients per year, which is comparable to the background population. The mean age was significantly lower in IBD patients than in non-IBD patients (53 versus 64 years, P= 0.0225). We found one patient with antithrombin deficiency but none with protein C, protein S, or plasminogen deficiency. Factor V mutation was as prevalent in IBD patients with thrombosis as in thrombotic non-IBD patients (27% versus 28%) and 3.0 times (95% confidence interval, 0.8-11.9) more frequent in IBD patients with thrombosis than in healthy controls. Prothrombin mutation was not detected in IBD patients with venous thrombosis.
Conclusion: We found no increased incidence of venous thrombosis in IBD patients compared with a background population. However, IBD patients had venous thrombosis earlier in life than non-IBD patients. Although factor V mutation may contribute to thrombosis, IBD acts as a trigger through mechanisms that still remain unexplained.