The urethra is the muscular tube that carries urine from the bladder to the exterior of the body. In horses it is the final segment of the urinary tract, connecting the bladder neck directly to the urethral opening.
Anatomy differs markedly by sex. In mares the urethra is short (approximately 8 cm) and opens onto the floor of the vestibule, just cranial to the vaginal opening. In stallions and geldings it is considerably longer, running the full length of the penis to the urethral process at the glans; the terminal section passes through the erectile tissue of the corpus spongiosum. This anatomical difference means that urethral obstruction from uroliths (calculi) is far more common in males, where the narrow urethral process and ischial arch create two natural constriction points. In mares, calculi typically lodge in the bladder rather than the urethra itself.
Urethral dysfunction is evaluated via endoscopy (urethroscopy) when signs such as straining to urinate, haematuria, or abnormal urethral discharge are present. See Equine Kidney for the upstream anatomy.
Further Reading
- Urethra on Wikipedia
- Overview of Urinary Tract Disorders in Horses