Incontinence, defined as inappropriate urine leakage for any reason, is a very common cause for veterinary visits, especially in spayed bitches. Incontinence occurs for many reasons, and the importance of a veterinary examination at the onset of symptoms, entailing rigorous owner questioning, a thorough physical examination (including assessment of neurologic function), and urine and blood testing cannot be overemphasized. Causes of urine leakage (from most common to least common) may be due to weakness in the urethral sphincters, increased amounts of urine in the bladder, structural abnormalities in the bladder, ureters or urethra which impair normal storage function, or a hyperactivity of the bladder muscle. Most cases of incontinence in the bitch can be managed and controlled, but a systematic work-up at the beginning of an incontinence problem is instrumental to ascertaining an accurate diagnosis and thus to directing appropriate therapy.

Urethral sphincter incompetence

The majority of incontinence cases in spayed bitches are due to relative incompetence of bladder closure mechanisms. Normal upper urethral tone and a healthy urethral mucosal lining are important factors in maintaining continence. Proposed contributing mechanisms for "spay incontinence" or "reproductive hormone-responsive incontinence" (RHRI) include relative estrogen deficiency, decreased responsiveness of urethral receptors to estrogen, aging, and obesity. The estrogen deficiency that occurs with ovariohysterectomy (spay) can result in structural changes in the urogenital tract. The urethral sphincter may lose tone, and the urethral mucosal lining may atrophy, resulting in a less tight seal to the system. Estrogen may also be important in the normal synthesis and maintenance of collagen, the chief component of connective tissues that structurally support the urinary tract.

The two main medical therapies used for this type of incontinence are estrogens (DES or PremarinÒ , primarily) or phenylpropanolamine (PPA). Estrogens are usually given in a "loading" phase once a day for 5-7 days, then are tapered back to 1-2 times per week (for DES) or 3-4 times a week (for PremarinÒ ). Estrogens are effective in controlling or improving signs in 50-65% of dogs with RHRI. Estrogens may help to restore the health and structural integrity of the urethral connective tissues and mucosa. Overdose of estrogens can lead to the serious side effect of suppression of the bone marrow or to less serious side effects such as signs of estrus ("heat") and other behavioral changes. Marrow suppression is uncommon with appropriate dosing (no more than 1 mg every 3 days for DES in a large dog), but dogs on long-term therapy should have periodic blood count monitoring performed. When dosed and monitored appropriately, estrogen therapy is safe and should be considered a first-line treatment for RHRI.

Phenylpropanolamine is a nervous system stimulant, which increases the production and release of the neurotransmitters that help to close the urethral sphincters. Response to PPA is generally excellent, with 75-90% of dogs with RHRI showing improvement in or complete control of incontinence signs. Phenylpropanolamine is administered 1-3 times a day, and many dogs will not be controlled with less than 3 times a day administration. Side effects of PPA vary from dog to dog, but relate to stimulation of the nervous system and include weight loss, anxiety, restlessness, excitability, fast heart rates, and sometimes gastrointestinal upset. When adverse effects occur, they’re usually related to the drug dose, and may resolve with decreasing the amount of PPA given. Many dogs have no problems at all with PPA. Because of the potential effects on the cardiovascular system these drugs should be avoided or used with extreme caution in dogs with heart disease, kidney disease, or high blood pressure. Phenylpropanolamine and estrogen work by different mechanisms and are synergistic (have a greater effect when used in combination than when used separately) in the treatment of RHRI. A bitch who cannot be controlled on either agent alone (or doesn’t tolerate therapeutic doses of PPA) may achieve symptomatic relief or control on lower doses of PPA in combination with estrogen.

A thorough neurologic examination will help to rule a spinal cord problem in or out. Though this is a much less common cause of incontinence in dogs, it is a potentially serious one and should be excluded as a cause early in the evaluation process. Your veterinarian should closely examine your dog’s feet, tail, anal tone and hind leg reflexes. He or she should also look for lower back pain. If evidence of neurologic disease is present, your veterinarian will recommend an additional series of tests to determine the origin of the symptoms and the available therapeutic options.

Urinary tract infection (UTI) can cause irritation of the urethra and "loosen" an otherwise functional urethral sphincter. A urinalysis and urine culture should be part of every initial incontinence evaluation to rule this very treatable cause of incontinence in or out. Additionally, incontinence can predispose to UTI by decreasing the tightness of the urethral seal and allowing bacteria to enter the bladder. Common signs of UTI include increased frequency of urination (small amounts each time), straining while urinating and/or blood in the urine. You may also see your dog licking her vulva frequently or "scooting" it on the ground.

Increased urine production

Any systemic disease that causes increased urine production can lead to incontinence, just due to overflow from unusually large amounts of urine present in the bladder. Many diseases such as diabetes mellitus, kidney failure, adrenal insufficiency or overactivity, uterine infection or kidney infection, as well as prescribed medications such as steroids, LasixÒ and phenobarbital, cause increased drinking and can result in overflow incontinence. Knowing your dog’s medication protocol and measuring water intake can help your veterinarian rule this in or out as a causative factor. A urinalysis and chemistry panel are critical to start ruling these diseases in or out. If, based on clinical signs and initial blood and urine values, your veterinarian suspects a metabolic disease or an infection, other blood, urine or radiographic evaluations may be indicated.

Structural abnormalities of the bladder and urethra

Positioning of the bladder within the pelvis instead of the abdomen is thought to promote incontinence in women and many practitioners feel the same is true in bitches. Often this pelvic bladder position is accompanied by a shorter, wider urethra, and these dogs generally present for incontinence early in life. Surgical repositioning of the bladder (colposuspension) will help some of these dogs.

Another cause of incontinence that manifests in early puppyhood is the presence of an ectopic ureter. In this congenital (present from birth) condition, the ureter (the tube that connects the kidney to the bladder) opens into the urethra instead of into the bladder. These dogs usually dribble urine constantly, and clinical signs are present from birth. Surgical correction of the problem is successful about 50% of the time, but often these dogs have multiple structural urogenital abnormalities

The presence of a mass in the bladder or urethra will occasionally alter the structure and function of these organs in a manner that leads to incontinence. Additionally, chronic bladder disease can cause a loss of bladder wall elasticity and thus can diminish urine-holding capacity. These causes of incontinence are uncommon.

Hyperactivity of the bladder

Detrusor (bladder muscle) hyperactivity is a very uncommon cause of incontinence in dogs. Diagnosis requires specialized eletrophysiologic testing only available at some teaching hospitals.

Before you see your veterinarian

Your observations of your dog’s habits can help your veterinarian tremendously in pinpointing the cause of incontinence, and thus in directing appropriate, effective therapy. When taking your pet in for evaluation of an incontinence problem, think about and be able to answer the following questions:

1. How long ago did you first notice this problem?
2. When does the leakage occur (only at night, when excited, all the time, when resting)?
3. Is your dog drinking less or more than usual?
4. Does she ask to go out more frequently?
5. Does she still posture to urinate normally?
6. When she goes outside, does she squat in many different places or urinate longer in one spot than usual?
7. Is she ever fecally incontinent (does she defecate without realizing it)?
8. Does she ever scuff her back feet (look at the tops of her back feet and at the hind toenails)?
9. Are her appetite and behavior otherwise normal?
10. Does she have any other health problems? Have they changed?