Q: I am a 55-year-old male, and I had an episode where my urine turned bloody. What can cause this?


A: The urinary system is made up of two kidneys that filter about 200 quarts of blood per day (to remove waste and maintain the body’s fluid balance) and one bladder to hold the urine until we excrete it. There are also two tubes, one from each kidney, that carry the urine to the bladder (ureters), and one urethra through which we urinate. Many things can affect the urinary system to cause blood in the urine (called hematuria).

Up to 20 percent or more of the population will have blood in their urine at some time in their lives. Most of the time this is just a small amount of blood, only detectable under a microscope. However, up to a third of these cases will have the urine become pink, cola colored or even reddish; as little as 20 drops (a milliliter or about a fifth of a teaspoon) of blood in one quart (or liter) of urine can visibly change the urine’s color (called gross hematuria).

The first step in evaluating possible gross hematuria is verifying that the color change is due to blood; many other things can color someone’s urine, including certain medications, foods (such as beets or blueberries), food coloring, medical conditions (porphyria, methemoglobinemia and others) as well as high blood content of certain metabolites (for example bilirubin). Urine testing will include a chemical analysis (usually done by dipping a test strip in the urine), as well as an examination of the urine under a microscope.

Common causes of hematuria in an adult include:

- Infections, such as the parasitic infection schistosomiasis (not endemic in the U.S. but common in certain other countries) or other parasites, certain viral infections and many types of bacterial infections. In fact, most women will have at least one bacterial urine infection in their lives.

- Inflammation of any of the organs of the urinary system.

 - Mechanical causes, including kidney stones, blockage due to narrowing of a ureter or the urethra (from strictures or compression from surrounding structures), trauma, or even strenuous exercise. For example, one study showed that over 20 percent of ultra-marathoners develop at least microscopic hematuria after a race.

 - Prostate conditions in men, which become much more common with advancing age. Even a benign enlarged prostate may be associated with hematuria.

- Cancer of any of the urinary system organs, whether kidney cancer, bladder cancer, prostate cancer or others.

- Blood disorders that allow the patient to bleed more easily, such as low platelets (from any cause) and others.

- Certain medications.

- Other medical conditions, such as sickle cell disease (much more common in African Americans), diabetes, and others.

Once hematuria is confirmed, a complete physical examination and history should be done to look for indications of a specific cause. The initial urine tests can be helpful; for example, red cell casts (a specific microscopic finding) strongly point to an inflammatory process (glomerulonephritis or vasculitis). A culture of the urine is typically done to look for bacterial infections. Urine cytology (microscopic evaluation of the urine for cancer cells) may also be indicated. Blood tests to look for bleeding disorders, and to rule out other metabolic conditions, are usually done.

Imaging tests may include computed tomography urography (felt to be the best test to evaluate the upper urinary system by many urologists), ultrasound or even MRI. Cystoscopy, where a thin tube with a miniature camera on the end of it is inserted through the urethra into the bladder, is the best method to directly visualize the bladder, and enables a biopsy to be done if required.

Treatment of hematuria is aimed at the causes identified from the evaluations discussed above. However, despite appropriate evaluation over 10 percent of cases have no cause identified.

When no cause of hematuria is found, the patient may benefit from follow-up to identify possible early developing cancers, even though studies have shown that this diagnosis is eventually made in less than 3 percent of these negative initial work-up patients; since early cancer diagnosis is beneficial, many physicians recommend repeat urine cytology regularly for up to 3 years after the initial work-up. If gross hematuria recurs, or there is a positive cytology, a complete repeat work up may be indicated.
