Urinary incontinence is the lack of complete, voluntary control over the passage of urine. It results from the failure of the bladder and / or urethra (the outlet from the bladder) to contain urine when the bladder fills. In dogs, the most common cause of this is known as “urethral sphincter mechanism incompetence” (USMI). It is most common in neutered women. Other names for this condition include idiopathic incontinence, hormone sensitive incontinence, and spay incontinence.
Spay incontinence is a fairly common condition and has received much discussion and research in medical circles, as is often the case when science has not yet been able to definitively understand it. Why is this happening? What exactly is going wrong physiologically? These questions have not yet been finally answered.
WHAT WE KNOW
During urination, involuntary nerves instruct the bladder to contract and relax the urethra. The opposite happens when urine is held; The bladder needs to relax and the urethra needs to contract.
There are estrogen receptor sites along the urethra, supportive ligaments, and muscles. When estrogen binds to these receptors, the tone of the urethral sphincter increases. There are other receptors (alpha receptors) that also strengthen urethral tone. It is known that estrogen increases the number and sensitivity of these receptors.
A conventional spay operation (more formally known as ovariohysterectomy) is the removal of a dog’s ovaries (along with its uterus). This means that it no longer produces estrogen and thereby loses these strengthening effects. When the muscles and the sphincter weaken, the urethra becomes less effective in holding back urine and urine can leak.
About 5% of neutered bitches develop urinary incontinence. Of these, the vast majority are larger dogs weighing 40 pounds or more. In the US, Dobermans and Giant Schnauzers top the list of breeds with the highest incidence, while in Europe it is the boxer.
The time of the start is very different. Spay incontinence usually occurs within three years of spay surgery, although some dogs develop symptoms within weeks of surgery.
STILL FOR THE DEBATE
Experts disagree about the ideal time to have spay surgery and whether the age of the dog at the time of surgery affects the likelihood of developing urinary incontinence afterward. There are studies that show that if you neuter them young (under 6 months), it is more likely. There are also studies that say it makes no difference whether you castrate them sooner or later (after 12 months).
It is unclear whether neutering makes a difference before or after the first run. Why are the larger races affected so much more often than the smaller ones? We just don’t know. There is at least one study that implies that spaying and neutering the larger breeds later may help reduce the incidence of castration incontinence. In addition, the debate continues.
If you notice your spayed bitch starting to leave moist spots to lie on, she may be suffering from spontaneous incontinence. Other signs include wetness around the vulva, discoloration of the hair around the vulva, paying more attention, and licking the vulva. Leakage is almost always intermittent and usually most noticeable after resting or sleeping. She will still urinate normally when taken to the potty as long as there are no other compounding problems like a urinary tract infection (UTI).
WHAT TO DO
Make an appointment with your veterinarian and be sure to bring a fresh urine sample (no older than 30 minutes) that has been collected in a clean, dry container. I find it easiest to use something with a larger diameter, low profile to collect urine. Just casually slide something low like a cake plate (as opposed to a Dixie cup) behind your dog when he crouches to urinate.
After collecting the urine, pour it into a clean, dry container to give to your veterinarian. The fresher the sample, the more accurate the results. So it’s not a bad idea to take your cake plate and container to the clinic and catch your sample right outside the door.
In addition to performing a urinalysis on the sample you brought with you, your veterinarian will perform a thorough physical exam, including a neurological exam and rectal palpation. A careful medical history is taken to determine the exact nature of the leak:
• Is it intermittent or consistent?
• Large quantities or small puddles?
• After training or after a break?
• Does it only occur while lying down or does it trickle when walking?
• Does she usually urinate outside?
The urinalysis, exam, and answers to these questions will help your veterinarian rule out other underlying conditions that may contribute to urinary incontinence. This includes things like spinal cord disease, kidney disease, urinary tract infection, bladder stones, and diabetes.
If everything is normal at this point, your leaky dog will likely be diagnosed with spay incontinence until proven otherwise. There are urethral pressure tests that can be done to prove that this is USMI, but they are expensive and will put your dog through many potentially unnecessary tests. Because the treatments available for spay incontinence are safe and effective, it is acceptable to start treatment and use a positive response to therapy as a diagnostic tool.
Medical therapy falls into two groups: hormone replacement (estrogen) and drugs that strengthen the contraction of the involuntary muscles of the urethra (alpha agonists).
Phenylpropanolamine (PPA), an alpha agonist, is usually the drug of choice. The popular brand name is Proin, made by Pegasus Laboratories. PPA is effective in 75% to 90% of dogs with spay incontinence. It’s relatively safe, but it can cause high blood pressure. Your dog’s blood pressure should be checked a week later, again in a month, and then every six months then, before starting therapy. Other possible side effects are restlessness and restlessness.
Typically, dogs are started on PPA twice a day. Some dogs may be kept on a once-a-day dosage. Some dogs may need medication three times a day. Proin is also available in an extended-release formulation, which is preferable for dogs requiring three times daily dosing of the regular formula.
Dogs with high blood pressure, kidney disease, or heart disease should not be treated with PPA. Hormone replacement therapy is a better choice for these dogs.
Diethylstilbsterol (DES) is the original synthetic estrogen that was prescribed to treat spay incontinence. Medical concerns for human patients have made this drug more difficult to find, but it is available through veterinary medicines. After charging once a day for a week, many dogs can be treated once a week.
At the dosages prescribed for urinary incontinence, this drug is safe. However, at higher doses or in the event of an accidental overdose, this leads to life-threatening bone marrow suppression. So put it high on a shelf that your dog cannot get on.
Estriol is a newer, more popular estrogen. The brand name is Incurin, manufactured by Intervet Schering-Plow. This is a short-acting estrogen that is extremely safe. It is dosed once a day. After the first two week loading time, it is recommended that lower dosages try to find the lowest effective dose for your dog. Sometimes this drug can cause loss of appetite and vomiting. When the dose your dog needs for effective control is high, he sometimes shows unwanted signs of heat (swollen vulva, male dog alert). In this case, PPA might be a better choice.
If you’ve tried Proin to no avail and then tried Incurin and still had no luck stopping the urine drip, ask your veterinarian if you’d like to try them together. They are safe to use together and there is often a synergistic boosting effect.
Any medication or combination of medications that will work for your dog may become less effective over time. Therefore, expect ups and downs and the need for medication adjustments. Other drugs sometimes tried in refractory cases include conjugated estrogens (e.g. Premarin) and GnRH agonists (e.g. Lupron). Surgical options are available for dogs who have not been given medication.
Urinary incontinence due to incompetence in the sphincter mechanism makes your dog more prone to urinary tract infections. Therefore, have your urine checked regularly. This should be the first thing you do when your previously well-controlled incontinent dog starts licking again.
In most cases, medication can safely and effectively treat this frustrating, annoying problem. If this happens to your neutered wife, don’t lose hope!