Causes of Red Urine in Horses Reviewed

Causes of Red Urine in Horses Reviewed

Bloody urine can be caused by a variety of conditions, some as innocent as a bladder stone or a urinary tract infection while others include life-threatening cancers or tears in the lining of the urinary tract.


In veterinary school, students are taught that urine is the "golden elixir of life"; if urine isn't produced normally, the animal's health is in danger. So what happens if your horse's golden elixir suddenly turns blood red?

"Bloody urine can be caused by a variety of conditions, some as innocent as a bladder stone or a urinary tract infection while others include life-threatening cancers or tears in the lining of the urinary tract," explained Hal Schott II, DVM, PhD, Dipl. ACVIM, professor of equine medicine at Michigan State University's College of Veterinary Medicine, during his presentation at the 12th Congress of The World Equine Veterinary Association, held Nov. 2-6, 2011, in Hyderabad, India.

During his review presentation Schott highlighted three less common causes of bloody urine (called hematuria) in horses:

Exercise-associated hematuria is caused by the abdominal organs pounding the bladder against the pelvis during exercise. This trauma leads to ulceration of the inner lining of the bladder and is more likely to occur in horses that empty their bladder immediately before exercising or in horses that exercise for a long time (such as endurance horses).

"This diagnosis should only be made after other more common causes of hematuria have been ruled out, such as a bladder stone," advised Schott.

Urethral tears occur in stallions and geldings, Schott explained, and Quarter Horses or Quarter Horse crosses are believed to be more commonly affected than other breeds. Horses with tears void a normal volume and color of urine, but at the end of urination a series of urethral contractions occur that squirt out bright red urine. The blood results from a tear in the urethra (the tube that urine travels through from the bladder to the end of the penis) at a point called the ischial arch (a bony part of the pelvis).

"Because the ischial arch is relatively far from the tip of the penis, a tear in this region of the urethra can only be diagnosed via high-resolution videoendoscope," Schott said. "This condition is likely more common than we think because it is either frequently missed or misdiagnosed as a urinary tract infection and in many cases resolves on its own. If the condition persists for more than a month or if they develop anemia, however, surgery is needed."

Idiopathic renal hematuria is more distinct than the two aforementioned causes of bloody urine in that large clots of blood are frequently noted in the urine. In affected horses, the blood comes from one or both kidneys. In some cases blood from the kidneys can be caused by renal adenocarcinoma or abnormal blood vessel anatomy (e.g., arteriovenous fistula). Veterinarians refer to cases in which an underlying cause is never found as idiopathic. Both male and female horses can develop this condition, and Arabian or part-Arabian horses appear more commonly affected than other breeds.

"Treatment can include repeated blood transfusions and administration of drugs that promote blood clotting," suggested Schott. "In some horses with kidney cancer or an abnormal blood vessel, surgical removal of the kidney may be necessary.

"In contrast, surgical treatment of Arabian horses with idiopathic renal hematuria by removing the affected kidney is no longer recommended as affected horses may develop idiopathic renal hematuria in the remaining kidney after removing the first kidney," Schott noted.

A full summary of Schott's presentation will be available for free on the International Veterinary Information System.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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