It usually happens to older female dogs. They have their favorite spots to lie around and when they get up it looks like those spots are wet. Then they get up on the couch with you one evening and you know for sure. Your dog is leaking urine, in the house, on the couch, on your lap. This is not good. Fifty or sixty years ago it was common for dogs to live outside. They might come in during a particularly terrible storm or a really cold night but for the most part they lived outside. If they leaked urine, no one noticed. Now dogs sleep in our beds, I'm not exactly sure how that transition occurred but it would be an interesting sociological study. When your dog, who sleeps in your bed, leaks urine, you notice.
Diagnosing the incontinent dog is fairly straight forward. The first thing you want to be certain of is that your pup is not urinating on purpose. If they are this is not incontinence and we can move on from there. Once we have determined that your pup is leaking urine involuntarily we will want to perform a complete physical exam. Feeling for bladder tone, trying to express a bit of urine manually and getting an impression of your dog's overall health is a good place to start diagnostically speaking. Once we have an idea about the possible problems your pup is facing we will most likely recommend two laboratory tests, a blood panel and a urine culture. These two tests will rule in or out nearly 90% of the causes of incontinence. If these come back with no abnormalities that would explain the issue we can comfortably start talking about a weak bladder sphincter. Weak bladder sphincter is a common problem for female dogs affecting up to 20% of the population. In these cases the muscle that holds urine in is weakened and when Fluffy relaxes, her muscles also relax and small (or in bad cases large) amounts of urine leak out of her.
There are several physiological and anatomic factors that are implicated in the mechanism behind this form of incontinence in dogs. Ultimately however, we do not have a complete understanding of how this works. If we did we would probably be better at preventing it. Fortunately, we are fairly good at treating weak bladder sphincter incontinence.
We will typically start these patients on a drug called phenylpropanolamine (PPA). This drug directly stimulates receptors in the urethra and it causes the release of norepinepherine. Both of these actions help to increase sphincter tone. Side effects of this drug include restlessness, anorexia, irritability and hypertension. We often recommend monitoring blood pressure while on this medication and dropping the dose back a bit if we start to see changes in the blood pressure measurements.
Sometimes PPA doesn't work, sometimes it works for a little while but then doesn't seem to cut it anymore. In those cases we will often add or substitute in Diethylstilbestrol (DES). DES is a synthetic non steroidal estrogen. It is used at a loading dose and then tapered to the lowest effective dose to control incontinence. If you are familiar with pharmacological history in the United States you might have heard of DES. DES was used in human medicine up until the 1980's for estrogen replacement therapy and to deal with inflammatory conditions associated with the female urogenital tract. It was discontinued in human medicine after some very serious adverse health links were found. Fortunately, we have not been able to document the same health links in our canine or feline patients.
Males with urinary incontinence are typically given testosterone to treat urinary incontinence when PPA is not working. Testosterone also has a synthetic non steroidal oral form but the injectable steroid form is much more effective.
When all else fails or if you are not getting 100% resolution with medication alone there are surgical options. These include tacking the bladder and/or urethra to the body wall or other organs to increase the pressure on the urethra. There are also collagen or other bulking agent injections that can be given using a long scope to increase resistance and decrease incontinence. No surgical approach is going to offer life long resolution but may help lower doses of medications.
There are lots of reasons a dog could be leaking urine and getting to the bottom of incontinence is a lot like any other medical problem in our pets. The answer starts with a good physical exam by your veterinarian.