Urethral Defects Causing Hematuria in Adult Male Horses

The cause of urethral defects is not proved, but they are believed to occur because of high pressure in the corpus spongiosum at the end of urination in geldings or during ejaculation in stallions. This high pressure may cause a "blow-out" tear in the urethral mucosa.

• Diagnosis based on clinical signs and urethral endoscopy

The clinical signs of urethral defects are limited to hematuria at the end of urination, associated with contractions of the bulbourethral muscle in geldings or with hemospermia and decreased fertility in stallions. All breeds may be affected, although the disorder seems more common in Quarter horses.

Urethral defect, horse

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Courtesy of Dr. Thomas J. Divers.

Diagnosis of a urethral defect is based on clinical signs and urethral endoscopic findings. The urethral defect is seen in most cases on the dorsal convex surface of the urethra at the level of the ischial arch.

• Urethrotomy or other surgery to reduce urethral pressure and allow defect to heal

Some cases of urethral defect may heal spontaneously, but most continue with intermittent hemorrhage, although anemia is very rare. Breeding rest is recommended for stallions. Subischial perineal urethrotomy or corpus spongiotomy reduces vascular pressure in the corpus spongiosum during urination and ejaculation, allowing the defect to heal. A buccal mucosal graft and topical cautery have also been used to repair the defect.

• Glass KG, Arnold CE, Varner DD, Chaffin MK, Schumacher J. Signalment, clinical features, and outcome for male horses with urethral rents following perineal urethrotomy or corpus spongiotomy: 33 cases (1989-2013). J Am Vet Med Assoc, 2016, 249(12):1421–1427.

• Also see pet health content regarding noninfectious diseases of the urinary system in horses.