Urinary incontinence is a relatively common problem in small animals with a variety of etiologies. One of the more familiar
and frustrating conditions is probably urethral sphincter mechanism incompetence (USMI) which most often occurs in adult spayed
female dogs. Surgery is not the first or even second line of treatment for these animals. The first thing to do is to rule
out other possible underlying conditions that would cause or contribute to urinary incontinence such as ectopic ureters, vaginal
strictures, redundant epivulvar folds, chronic urinary tract infection, and neurological disorders. The second course of
action is medical management primarily consisting estrogen therapy, phenylpropanolamine, or combination therapy. When dogs
are unresponsive to medical treatment or if there are concurrent problems that limit the use of appropriate drugs, surgical
intervention may be considered.
Aside from decreased resistance in the urethral sphincter mechanism, animals with USMI typically have other anatomical factors
that may contribute to urinary incontinence, particularly a shorter functional urethra and intrapelvic positioning of the
bladder. Therefore, the goal of most surgeries for urinary incontinence is to increase urethral sphincter resistance, increase
the functional length of the urethra, or move the bladder and trigone into an intra-abdominal location.
Colposuspension
Colposuspension is the most common surgery used to address USMI in female dogs. This procedure involves placement of sutures
from the cranial vagina to the prepubic tendon on either side of the proximal urethra, thereby positioning the proximal urethra
within the abdomen and placing pressure on the urethra as it crosses the pubic brim. Several studies have looked the long-term
outcome following colposuspension. One of the most recent studies reported a response rate of 82% with half of those animals
completely continent without medication. These results are in contrast to a separate study which reported only a 54% response
rate, although a client satisfaction rate of 86% was also found. Prior to performing surgery, a large urethral catheter is placed. A caudal midline abdominal approach is performed and the
vagina is identified dorsal to the urethra. Stay sutures or atraumatic forceps are used to manipulate the vagina cranially.
Two sutures of heavy gauge (0 to 2-0) nonabsorbable monofilament are placed through the vaginal wall on either side of the
urethra to the prepubic tendon on either side of midline. The urethral catheter is used to prevent overtightening of the
sutures which may result in urethral obstruction.
Cystopexy
Cystopexy is a relatively simple procedure that involves permanently securing the urinary bladder in a more proximal direction.
By fixing the bladder within the abdominal cavity, the trigone and proximal urethra are exposed to intra-abdominal pressure
that may improve the tone of the upper urethral sphincter.
A routine caudal abdominal midline incision is made. There is usually no indication to perform a cystotomy. A stay suture
is placed in the apex of the bladder to facilitate manipulation and positioning of the bladder. The bladder is positioned
cranially in the abdomen without excessive tension. A #15 scalpel blade is used to gently scarify the ventral bladder wall
for most of the length of the body. An area of similar size is created on the ventral body wall just to the right or left
of midline. It is not recommended to incorporate the bladder wall in the abdominal wall closure. One or two rows of suture
with a simple continuous pattern using 3-0 or 4-0 monofilament, absorbable suture are placed to fix the bladder to the body
wall. Suture should be placed partial-thickness into the bladder, but absorbable suture is used in case of inadvertent luminal
penetration. Following removal of the stay suture, the abdominal wall, subcutaneous tissue, and skin are closed routinely.
