Ask The Doctor: Blood in Urin... Health Article

Howard LeWine, M.D., is chief editor of Internet Publishing at Harvard Health Publications. He is recognized as an outstanding clinician and teacher and is a recipient of the Internal Medicine Teacher of the Year award at Brigham and Women's Hospital. Dr. LeWine continues to practice Internal Medicine; most recently he became a hospitalist after practicing primary care for over 20 years.

Question:

I have been running for 10 years. Just recently, I started seeing blood in my urine just after running. What could cause this?

Answer:

A small number of red blood cells frequently escape from the kidney into the urine during a vigorous run. In one study of 10 competitive middle-distance runners who gave an average of seven samples each, nine of the athletes showed microscopic amounts of blood in the urine at least once following a practice session.

If enough red blood cells or fragments of red cells escape in the urine, the blood will be visible to the naked eye. This is well described in runners and soldiers who have had to march long distances. Doctors call this "march hematuria." The medical term for blood in the urine is hematuria.

When a runner develops this as a new problem, I recommend diagnostic evaluation that includes a urine analysis, blood tests for kidney function known as creatinine or blood urea nitrogen (BUN), a red blood cell and hemoglobin count, and usually an image of the kidney with CT scan or ultrasound. Depending on your age, your doctor may also want to refer you to a urologist for cystoscopy, a procedure that allows the doctor to see inside your bladder.