Urinary incontinence (UI) is the involuntary loss of urine during the filling phase of the bladder during recumbency and/or standing.
• Dogs of any age or sex may present with UI but it is more prevalent in spayed females (accounting for about 80% of adult cases), female dogs spayed prior to 3 months of age, and tail-docked bitches.
• UI is sometimes observed in prepubertal dogs due to congenital conditions.
• Urethral sphincter mechanism incompetence (USMI)-a reduced urethral closure that commonly develops after spaying
• Bladder neoplasia
• Vaginal neoplasia
• Prostatic surgery
• Ureterovaginal fistula
• Acquired neurologic condition
• Chronic urine retention
• Detrusor instability
• Ureteral ectopia
• Congenital USMI
• Bladder hypoplasia
• Intersex condition
• Pervious urachus
• Congenital neurologic condition
Previously continent animals
• Prepubertal gonadectomy in females, especially if performed prior to 3 months of age
• Surgery to uterus, prostate, bladder, or urethra
• Tail docking in females
UI therapy can be medical, surgical, or a combination of both.
• In USMI, medication should be the first course of treatment. In animals refractory to medical treatment, surgery may solve the problem or at least reduce drug dependence, which is often a lifelong consideration.
• Pain medication is not usually necessary in UI.
• Surgery is the treatment of choice when UI is caused by urogenital tract neoplasia or anatomic defects. A surgical approach includes directly or indirectly correcting the proximal urethra so the bladder neck is within the abdominal cavity and the urethral lumen is somewhat restricted. Techniques include colposuspension, urethropexy, cystourethropexy, transpelvic sling, and, in male dogs, deferentopexy or prostatopexy. Reduction of the urethral lumen can also be achieved through endoscopically injecting collagen under the urethral mucosa.
• Medical treatment should be discontinued before surgery (particularly estrogens, because their long-lasting effects on the reproductive system create a risk for dysuria following surgery).
• Colposuspension is the most popular procedure, while other techniques are used much less frequently. Regardless of surgical approach, approximately 50% of patients are cured, 40% show some improvement, and 10% show no improvement.
• Transient postsurgical dysuria is a common sequela, especially after colposuspension, because the urethra is compressed against the pubic bone or because of vagal stimulation during surgery. It can often be prevented by taking care not to place vaginal sutures too close to the urethra, but if it does occur can be controlled with diazepam (0.2 mg/kg orally 2 to 3 times daily) until normal micturition is regained.
• USMI often improves after puberty, so a decision on surgery should be postponed in prepubertal dogs.
Suture breakdown can be caused by the passing of large quantities of hard feces or by heavy exercise shortly after surgery. Intestinal contents must be evacuated prior to surgery and heavy exercise, running, or jumping should be avoided for at least 4 weeks following surgery.
• UI is often an intermittent disease. A subclinical condition may suddenly become clinical or a latency phase terminated as the result of:
- Fatigue or stress
- Weight gain
- Hot, humid weather
• Management of incontinent animals should include eliminating as much stress as possible and, provided that urine-concentrating capacities are normal as evidenced by hypersthenuric urine-specific gravity and normal urea nitrogen and creatinine concentration in plasma, maintaining a small bladder during periods of recumbency.
Continence is generally improved following administration of sympathetic/parasympathetic or estrogenic drugs. Efficacy tends to decrease over time despite increasing dosages, perhaps as a result of receptor desensitization. Because of the multifactorial character of this condition, no single treatment will be 100% effective.
• Many steroids have been used to treat canine UI, including 17β-estradiol, estradiol benzoate, estradiol valerate, diethylstilbestrol, estriol, conjugated estrogens, and, in male dogs, androgens. Short-acting estrogens such as estriol (characterized by short nuclear occupance time and minimal metabolism following absorption) show equal efficacy with other estrogenic compounds while avoiding estrogenic side effects such as endometrial hyperplasia, pyometra, and bone marrow suppression.
• Estriol is widely used at oral dosages of 0.5 mg/day to 2 mg/day. Its efficacy is approximately 80% to 85% with a fairly quick onset of action (several days).
• Treatment protocols should be started at a high dose (2 mg/day) for 1 week until continence is reached and gradually decreased (ie, 1.5 mg/day on week 2, 1 mg/day on week 3, and 0.5 mg/day on week 4). If the dog is continent on 0.5 mg/day, this dosage can be administered every second day on week 5, every third day on week 6, and weekly on week 7. If the dog becomes incontinent again, the dosage should be reverted to the previous one.
• Estradiol benzoate and diethylstilbestrol have been used in male dogs with some success, while androgens have yielded inconclusive results.
• Sympathomimetic (α-agonistic) drugs, which directly stimulate α-adrenergic receptors in the bladder neck and urethra, are widely used and highly effective (75% to 90%). They show a quick onset of action (several days) and require twice-daily or, most commonly, 3-times-daily oral administration.
• Phenylpropanolamine and ephedrine are the most effective α-agonists for bitches and are also fairly effective for male dogs.
• Unlike estriol, the best dose regimen of sympathomimetic drugs starts low (1 mg/kg, Q 8-12 H) and is titrated up (<_3 mg/kg Q 8-12 H) until good efficacy is reached.
• Anticholinergic drugs are sometimes used, especially when detrusor instability (uncommon in the dog) is suspected or when sympathomimetic drugs are not effective. Cholinergic receptors mediate detrusor contraction as well as relaxation of the external urethral sphincter. Inhibiting their action facilitates bladder filling and prolongs the interval between voiding phases.
• Commonly used anticholinergics include propantheline (15 mg Q 8 H increasing to 30 mg Q 8 H) or oxybutinin (0.2 mg/kg Q 12 H increasing to Q 8 H).
Gonadotropin-releasing hormone (GnRH) agonists such as leuprolide, buserelin, triptorelin, or deslorelin provide long periods of continence in approximately 50% to 60% of treated animals. A deslorelin implant often results in complete continence or decreased drug dependence. The oil-based implant dissolves over time and does not need to be removed at the end of the treatment period (6 or 12 months).
• No hematologic side effects in chronic toxicity studies have been observed using estriol for up to 3 months at daily doses > 3 mg/kg.
• Vulvar swelling and attractiveness to males are occasionally observed in bitches treated with high doses of estriol (2 to 3 mg/day).
• Side effects of α-agonists are rare and include anorexia, weight loss, increased excitability, restlessness, tachycardia, and skin eruption.
• Deslorelin implants have no side effects in dogs.
Incontinent animals, especially neutered adults, should get regular exercise and follow a strictly controlled diet to avoid becoming overweight.
No specific monitoring is necessary when the animal is continent. In case of a prolonged phase of UI, urinalysis should be performed to rule out cystitis. UI is often intermittent, so animals living outdoors should be periodically checked for signs of UI to identify phases of recurrence.
Chronic UI, especially if untreated, will lead to the development of UTI. Dogs undergoing surgery may show temporary dysuria.
Resolution of UI usually takes less than a week both with medical and surgical approaches.
Minimal care is typically required at home and includes administration of an estriol pill daily or a sympathomimetic oral solution 2 to 3 times a day.
Medication is relatively inexpensive ($), while the cost of surgery, if required, varies depending on the approach, length of time the patient is under anesthesia, and the number of days as an inpatient ($$$$$).
Prognosis is generally guarded to good, with full recovery occurring in approximately 60% of cases, improvement of the condition in approximately 30%, and no improvement in 10%, regardless of whether a medical or surgical approach is used.
The author wishes to thank Dr. Alessandro Zotti, University of Padua, Italy, for providing the figures in this article.
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