Managing Urinary Incontinence

Non-neurological causes
Urinary incontinence can be caused by congenital anomalies (e.g. ectopic ureter), cystoliths and urethroliths, or multiple foalings. Unlike cystolithiasis in male horses that usually leads to dysuria and post exercise haematuria, incontinence is one of the more common complaints for mares with cystoliths. Further, pelvic canal trauma during parturition and dystocia is likely an under- recognised cause of urinary incontinence in mares.

Neurological causes
Neurological problems that may cause incontinence include equine herpesvirus-1 myelopathy, cauda equina neuritis, equine protozoal myeloencephalitis, cervical stenotic myelopathy (CSM), equine degenerative myelopathy (EDM), pelvic/sacral trauma, and intoxications. Incontinence is often described as a consequence of an upper motor neuron (UMN) or lower motor neuron (LMN) bladder. A turgid bladder, due to increased tone of both the detrusor and urethral sphincter, with forceful squirts of urine is the classic finding for an UMN bladder (lesion above sacral segments). This syndrome is termed detrusor hyperreflexia with detrusor- external sphincter dyssynergia (DH-DESD) in humans. In contrast, a LMN bladder is characterised by an enlarged, atonic bladder, termed detrusor arreflexia (DA), accompanied by overflow incontinence. However, the author has observed DA (a LMN bladder) in horses that have no apparent damage to sacral segments (i.e. with CSM or EDM). This may be due to the fact that control of bladder and urethral sphincter function is complex and incompletely understood. Thus, neural lesions can have variable effects on lower urinary tract function. For example, in a report of 284 people with spinal cord injuries, 85% with cervical injuries had DH (with or without DESD) while 15% had DA. In contrast, 64% of patients with sacral cord injury had DA while DH (with or without DESD) was found in 24%, and 12% had normal lower urinary tract function. [...]