Surgical Conditions of the Bladder and Urethra

Urethral rents
A rent in the urethral mucosa that communicates with the corpus spongiosum penis (CSP) is a cause of haematuria in geldings. The rent, the cause of which is unknown, is found on the caudal surface of the urethra where the urethra curves around the caudal aspect of the ischial arch. Affected geldings may exhibit signs of pain during urination, and haemorrhage occurs at the end of urination. During endoscopic examination of the urethra of affected horses, a 5 to 15 mm longitudinal rent is observed on the caudal surface of the urethra at the level of the ischium (Russell and Pollock 2012). Horses with a urethral rent experience haematuria because the intraluminal urethral pressure decreases suddenly at the end of urination while the pressure in the CSP remains high. The amount of haemorrhage varies from a few to several hundred millilitres of blood.

Haemospermia, a cause of infertility of stallions, can also be caused by a urethral rent identical to those identified in geldings with haematuria. Only rarely do stallions with haemospermia caused by a urethral rent have gross evidence of haematuria, but affected stallions probably have microscopic haematuria. The reason for the difference in clinical signs between stallions and geldings is that during urination, pressure within the CSP of geldings is nearly double that of stallions because the volume of the CSP of geldings is less than that of stallions. [...]