Correcting polyuric disorder could put incontinence on hold
Q. Please review urinary incontinence in dogs.
A. Dr. Jodi L. Westropp and Dennis J. Chew at the 2005 American College of Veterinary Internal Medicine Forum in Baltimore gave a lecture on urinary incontinence in dogs. Some relevant points in this lecture are provided below.
A thorough history from the owner that presents his/her dog with a micturition problem should be obtained. Differentiations should be made between pollakiuria, polyuria and urinary incontinence because each complaint is handled quite differently. A dog may also present with multiple problems such as urinary incontinence and polyuria. Depending on the underlying cause for the urinary incontinence, correcting the polyuric disorder may lead to significant improvement in urinary incontinence.Ectopic ureters are the most common underlying cause of urinary incontinence in young dogs and cats. The location of ectopic ureters typically occurs in the urinary bladder-urethra junction, various locations along the urethra, and rarely in the vestibule. Urinary incontinence is the most common clinical sign in dogs with ectopic ureters and is usually diagnosed in dogs before 1 year of age; however, ectopic ureters should be considered in any dog with urinary incontinence. Breeds reported to be at risk include the Golden Retriever, Labrador Retriever, Siberian Husky, Newfoundland and English Bulldog. Although unilateral ectopic ureters have been reported to be more common, bilateral ectopic ureters are significantly more common, which suggests that careful imaging of the urinary tract should be performed before surgery to obtain the best clinical outcome. Ectopic ureters are uncommon in male dogs.
A diagnosis of ectopic ureters can be made by excretory urography, fluoroscopic urethrography, abdominal ultrasound, cystoscopy, helical computed tomography (CT) or a combination of these diagnostic procedures. CT has the advantage of evaluating the entire urinary tract and has 91 percent sensitivity and 100 percent specificity, although this procedure is usually significantly more costly and requires referral. Urine cultures should always be performed in dogs with suspected ectopic ureters because urinary tract infections appear to be quite common with this disorder. Other congenital abnormalities can also occur in dogs with ectopic ureters such as a hypoplastic bladder or urethra, pelvic bladder, ureterocele, renal agenesis or hydroureter. For these reasons, it is essential to evaluate the entire urinary system prior to surgery.
The preferred treatment for dogs with ectopic ureters is surgical correction (success rates vary between 50-75 percent after surgery). The poor success rate could be due to a variety of causes including incorrectly identifying the terminal portion of the ectopic ureter, the presence of multiple ureteral openings, concurrent urethral sphincter mechanism incompetence or a combination of these. Urodynamic testing is recommended prior to surgery because abnormal urethral closure pressures in dogs with ectopic ureters are noted.
Decreased urethral closure pressure can occur due to malformations of the spinal vertebrae (Manx cats), dysautonomia and lumbosacral disorders such as intervertebral disc disease, degenerative myelopathy, diskospondylitis and trauma. A thorough neurologic examination should be performed on all dogs that present for urinary incontinence.
Urethral sphincter mechanism incompetence (USMI) (acquired urinary incontinence occurs mostly after spay) is a diagnosis of exclusion once all other disorders have been ruled out. Urinary incontinence can occur after spay of the female dog and the onset of signs can vary from immediately to 10 years after surgery. Leaking urine while asleep appears to be the most common complaint. Urinary incontinence can be daily or episodic and range from mild to very severe. There appears to be higher risk for larger breed dogs after spay compared to small breeds and certain breeds appear over-represented (German Shepherds, Boxers, Spaniels and Doberman Pinchers). The underlying cause of USMI is unclear and estrogen deficiency is probably not the sole cause of the urinary incontinence because estrogen concentrations are similar between continent anestrous dogs and incontinent spayed dogs.
Studies regarding the timing of neutering are contradictory, but according to the most recent data, early spaying (prior to the first heat cycle) had a reduced incidence of urinary incontinence (9.7 percent vs. 18 percent) in large-breed dogs. However the severity of the urinary incontinence was more pronounced in the early spay group. This relative disadvantage of early spaying is inconsequential when compared with the benefits of reduced incidence of urinary incontinence and protection against mammary tumors. The causes of USMI are probably multifactorial including hormone imbalances, genetics, obesity, age-related changes in urethral musculature and perhaps position of the neck of the urinary bladder.