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Inflammatory Bowel Disease Health Center

IBD Flare-ups May Increase Blood Clot Risk

Study Shows Active Inflammatory Bowel Disease May Be a Risk Factor for Blood Clots
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WebMD Health News
Reviewed by Louise Chang, MD

Feb. 9, 2010 -- Non-hospitalized patients with a flare-up of inflammatory bowel disease are 16 times more likely to develop potentially life-threatening blood clots as people without the bowel disorder, new research reveals.

While the risk is still quite small for individuals with Crohn's disease and ulcerative colitis, which are forms of inflammatory bowel disease (IBD), the findings suggest that active IBD is a bigger risk factor for blood clots than has been previously recognized.

Blood clots, known medically as venous thromboembolisms, can become deadly when they break away from the large veins in the legs or groin and move to the lungs. The Surgeon General estimates that between 300,000 and 1.2 million Americans experience such clots each year, and more than 100,000 die from them.

In earlier studies, researchers reported that most IBD patients who develop blood clots do so when their disease is symptomatic, rather than when it is in remission. For this reason, many hospitalized IBD patients receive anticlotting drugs like heparin to reduce their blood clot risk. But the risk to non-hospitalized IBD patients in the active, or flare-up, phase of the disease has not been well understood.

In an effort to assess this risk, researchers analyzed a database in the U.K. that included information on patients with and without IBD.

The analysis included 13,756 patients treated for IBD between November 1987 and July 2001 and 71,672 people without the disease who served as a comparison group.

Among the results:

  • Overall, IBD patients were 3.4 times more likely to develop a blood clot than people without IBD. 
  • This risk more than doubled among patients experiencing IBD flares. These symptomatic patients were eight times more likely to develop a clot as those without IBD. 
  • Patients hospitalized for a flare-up of IBD were three times as likely to develop a blood clot as patients hospitalized for other reasons.

While the overall risk for developing a blood clot was greatest among patients hospitalized with IBD, the relative risk was greatest for symptomatic IBD patients who were not hospitalized.

Compared to non-hospitalized people without IBD, these patients were 16 times more likely to develop a potentially life-threatening blood clot.

The study appears online Feb. 9 in The Lancet.

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