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Blood thinners often lead to blood in urine severe enough to require medical help, new study finds

Oct 3, 2017

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Many people on blood thinner medications will experience visible blood in the urine that is severe enough to require medical attention, a new study published today in JAMA has found.

The Sunnybrook-led study looked at the data of more than 2.5 million Ontarians aged 66 years or older. More than 800,000 were prescribed an antithrombotic medication in the study period. Over the 13-year study period, visible blood in the urine requiring medical intervention happened in 123 per 1000 people for those who had been on blood thinners versus 80 per 1000 people for those who hadn’t. Of the medical treatments required, there was a 2- to 6-fold risk of being hospitalized because of the severity of the blood in the urine.

Antithrombotics – blood thinners – include anti-coagulants and anti-platelets. Anticoagulants, such as warfarin, lengthen the time it takes to form a blood clot. Antiplatelet drugs, such as aspirin, prevent blood cells called platelets from joining together to form a clot. These medications are typically prescribed to people with heart disease, or those who are at risk of blood clots or stroke.

This study looked at these types of medications and also the newer forms, including apixiban, dabigatran and rivaroxaban. All types of these medications were associated with visible blood in the urine.

Blood in the urine was more common among older, sicker males. These patients had a five-fold increase in visiting the Emergency Room over those not on these medications.

The study also showed these blood thinners unmasked the presence of silent bladder cancer due to the bleeding at a rate that was more than twice that of the general population.

“This blood can cause distress, plug up the bladder, and lead to other complications like kidney failure, infection and the need for blood transfusions,” said Dr. Robert Nam, urologist at Sunnybrook and senior author on the study. “It is important that patients with blood in the urine do not ignore it, particularly when bladder cancer can be diagnosed at a much earlier stage.”

Dr. Nam says the study is not suggesting physicians or patients rethink the use of blood thinners to treat a particular condition.

“This study empowers us to say this complication is a problem for patients and for the health-care system. How can we work with patients to better manage this complication of blood in the urine to prevent patients from requiring the Emergency Department or hospitalization? How can we manage this complication better?”

He says the study can educate both physicians and patients about blood in the urine as a common complication from these medications.