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Collagen injections can correct canine incontinence

Its proven success rate for tough cases: more than 90 percent for 18 months

[From Tufts April 2011 Issue]

 Veterinarians have discovered that a technique used to make human skin look more youthful can cure difficult cases of canine incontinence—at least temporarily. A collagen injection into the urethral lining has been found to have a success rate of more than 90 percent for 18 months.

The bovine collagen used in veterinary medicine—the same used in people—increases pressure and tightens the urethra, the tube leading from the bladder to discharge urine. This fibrous protein also encourages the growth of new blood vessels. The injections are safe, though costly at about $1,000, and may need to be repeated when they lose effectiveness.

Dedicated owners
Some incontinent dogs might otherwise be euthanized when none of the other treatments worked. “Owners of these dogs are very dedicated and have tried everything, but can no longer deal with the unhygienic issues related to the incontinence,” says Linda Ross, DVM, MS, a specialist in small animal internal medicine at Cummings School of Veterinary Medicine at Tufts University. “Collagen injections may be able to correct the incontinence or at least result in enough improvement that medications will now work.”

Referral hospitals and some veterinary schools, including Cummings School, offer the procedure. It requires general anesthesia and a specialist to perform cystoscopy—the introduction of a scope to visualize the bladder and urethra.

In dogs, the most frequent cause of urinary incontinence is a lack of estrogen in older, spayed females, Dr. Ross says. “About 20 percent of older, spayed females are affected. Larger breeds in general are more commonly affected, particularly Doberman pinschers and giant schnauzers.”

The predominant symptom
In this type of incontinence, known as hormone-responsive incontinence, the most predominant symptom appears to be bedwetting. The dog may urinate in her sleep and wake up to find herself in a puddle. Other dogs may dribble urine while they walk or become excited.

Estrogen, a steroid hormone produced mainly in the ovaries and in smaller amounts in the adrenal glands, stimulates estrus (also known as the heat cycle) and helps provide tone to the urethral sphincter muscle. When dogs are spayed, veterinarians remove their ovaries. The decrease in estrogen results in a loss of muscle tone in the sphincter, which in turn diminishes the dog’s ability to hold urine. For many female dogs, the small amount of estrogen produced by the adrenal glands is sufficient to offset the loss of estrogen from the ovaries. But for that 20 percent minority, the adrenal glands can’t produce enough estrogen to maintain the bladder’s muscle tone and prevent urinary leakages.

This doesn’t mean that female dogs shouldn’t be spayed. Not at all, Dr. Ross says. “There are so many good reasons to spay dogs—population control, virtual elimination of the possibility of mammary cancer if the dog is spayed before her first heat and elimination of the possibility of uterine infection.”

Unconscious dribbing
Veterinarians diagnose incontinence by obtaining a history of unconscious dribbling of urine and performing a physical exam. They may also do other tests, including a urinalysis and urine culture to check for bacterial infection; a chemistry profile to check kidney and liver function; and ultrasound or special X-ray contrast dye studies to look for congenital abnormalities. In a condition called ectopic ureters, for example, some dogs are born with ureters—the tubes that connect the kidneys to the bladder—that empty into the uretha rather the bladder.

Two prescription medications constitute the first-line remedies for treating hormone-responsive incontinence. The first is diethylstilbestrol (DES), a synthetic compound with the same properties as natural estrogens. Administering DES for a few days may well be all that’s needed to enable the older female dog to hold her urine. The tiny pills are easy to slip into a dog’s food or soft treat. However, because DES has been known to cause miscarriages and birth defects in human babies, pregnant women or those trying to become pregnant shouldn’t administer the medication.

An effective human drug
The other drug is phenylpropanolamine (PPA). It was once used to suppress appetite and treat nasal congestion in humans, but has since been withdrawn. Nevertheless, the drug continues to be useful in treating hormone-responsive incontinence in dogs because it tightens the urethral sphincter, Dr. Ross says.

While DES and PPA are effective in alleviating most hormone-responsive incontinence, some severe cases require other measures. “These are usually used in dogs with congenital malformations of the urinary tract, but they could be used for spayed females if the drugs don’t work or if there is a medical contraindication for the drugs,” Dr. Ross says. “These treatments include several types of surgery, including placing silicone cuffs around the sphincter.”

Ectopic ureters are usually repaired surgically, although some hospitals are now correcting them with laser therapy.

Incontinence is not nearly as big a problem in male dogs as it is in females. “They can suffer from hormone-responsive incontinence—the lack of testosterone if the dog has been castrated—but it is very rare,” says Dr. Ross. “When a male dog has incontinence, we look for other causes. If the dog is young, we look for congenital anomalies of the anatomy of the urinary tract. If the dog is older, we look for bladder stones, cancer or neurological problems.”

Owners of dogs who dribble need to understand that the leakages generally don’t occur because of housetraining lapses. The overwhelming likelihood is that physical problems have developed that often can be easily fixed.

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