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.
Clinical Findings and Diagnosis
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.
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.
Bleeding at the end of urination or during ejaculation in adult male horses with no other clinical abnormalities is characteristic of a urethral tear.
Diagnosis is often made by urethral endoscopy.
Treatment may be required for breeding stallions if fertility is reduced.
For More Information
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 Noninfectious Diseases of the Urinary System in Horses Not every disease is caused by infection with bacteria, viruses, or other outside agents. There are a variety of noninfectious disorders that can impair the urinary system. All of these diseases... read more .