Urinary incontinence is the involuntary passing of urine. Pets can be incontinent for many different reasons. Those reasons can involve the bladder, the urethra which is the tube from the bladder to the outside, or incontinence can be caused by abnormalities in the parts of the brain and spinal cord that control bladder function. Incontinence can be confused with diseases that cause a pet to urinate frequently. A physical exam and laboratory tests will help in the proper diagnosis.
More than 20% of spayed females are affected with urinary incontinence. Both male and female dogs can be affected, with medium to large breeds being more prone for the problem. The number of cases is likely to increase with the growing number of older dogs, advances in geriatric veterinary care and significant amount of time pets spend indoors. Urethral Sphincter Mechanism Incompetence is the most commonly diagnosed cause of urinary incontinence: 81% of incontinent adult females and 57% of all dogs with involuntary urine loss. Phenylpropanolamine (PPA) is the most frequently dispensed medication for this type of incontinence.
Incontinence can be confused with submissive urination. Submissive urination occurs when a dog is acting submissive to a person or to another dog. Submissive urination occurs more frequently in young animals. The dog usually rolls on its back and urinates. These dogs can also urinate normally.
Young animals may have a birth defect causing incontinence. The most common birth defect that causes incontinence in young dogs is ectopic ureter(s). The ureters carry urine from the kidneys to the bladder. If one or both ureters by-pass the bladder and connect to an abnormal location such as the urethra or vagina, the puppy may drip urine. Siberian Huskies are most often affected. Other breeds that have a higher occurrence of this birth defect include:
- Miniature Poodle
- Labrador Retriever
- Collie
- Welsh Corgi
- Wire-haired Fox Terrier
- West Highland White Terrier
Female dogs are more commonly affected. If only one ureter is abnormal the dog will dribble urine but can also urinate normally. If both ureters are affected then the puppy will only dribble urine and cannot pass urine normally. To diagnose this condition a dye study of the bladder is usually performed. Sometimes the abnormal opening into the vagina can be seen during a careful examination under anesthesia using special equipment. Most puppies with ectopic ureter(s) also have a bladder infection that will improve with antibiotics but the infection will return until the problem is corrected. In some cases the ureter can be surgically moved back to the normal location in the bladder and incontinence may resolve. In other cases, long standing infection of the kidney may have damaged the kidney requiring the removal of one kidney. In yet other cases the abnormality of the ureter can be corrected but the pet remains incontinent, probably due to the presence of other birth defects in the urinary system.
A bladder infection can cause either a strong urge to urinate or if the bladder infection is long standing it can cause scarring of the bladder preventing it from stretching to hold urine. In this case the pet is usually not truly incontinent in that they know they are urinating, but they have such a strong urge to empty their bladder that they may urinate in abnormal locations or urinate very frequently. It is common to evaluate incontinent pets for the presence of a bladder infection.
Pets with a partial blockage of the urethra with a stone or a tumor may show incontinence. If they cannot empty their bladder completely because something is blocking the path to the outside, the bladder may get so large that the back pressure of urine in the bladder actually forces some urine to leak around the blockage. In these pets the enlarged bladder can be felt on examination. Total blockage of urine flow is usually fatal in 3 to 4 days.
Hormone-responsive incontinence occurs in neutered dogs of both sexes and occasionally in spayed female cats but occurs most commonly in female dogs. The pet can urinate normally, but they leak urine while resting. Physical examination and blood and urine tests are usually normal in these pets. Hormone-responsive incontinence can occur months to years after a pet is neutered. As pets age they may become incontinent. This may be due to a weakening of the muscles that hold urine in the bladder. There are many diseases that can cause a pet to create more urine than normal (polyuria) and several of these occur in older pets. If a pet has one of these diseases and often has a full bladder, the full bladder can push against the weakened sphincter and cause incontinence. Older pets can also develop senility and simply be unaware that they are dribbling urine.
Dogs with brain or spinal cord disease may either dribble urine or be unable to pass urine. Most often they will have other signs of nervous system disease such as muscle weakness or paralysis.
A less common cause of incontinence in female dogs is called vulvovaginal stenosis. It is a condition in which the vagina at the level where the urethra ends is narrowed. Occasionally when the pet urinates, some urine will get trapped in the vagina in front of this narrowed area. Then when they rise after lying down the urine pours out. This condition can be diagnosed by feeling the vagina with a gloved finger. In some dogs the narrowing can be stretched under anesthesia. The incontinence may or may not resolve as sometimes other defects are also present.
Diagnosis of incontinence
The tests performed to evaluate a pet with incontinence depend upon the age of the pet and on the presence or absence of other signs. It is common to collect a urine sample for bacterial culture and to see if the urine is dilute or shows evidence of an infection. Infections of the urine may be secondary to another cause of incontinence.
Questions that your veterinarian will ask to help identify the cause of your pets problem include:
- The age when incontinence first appeared
- When the incontinence is usually observed, for example at rest or with activity
- Whether the pet can urinate normally
- Previous surgeries (such as neutering) and illness
- Use of medications that might cause the urine to be dilute such as diuretics, anticonvulsants or prednisone
- How much water the pet drinks
- How frequently the pet urinates and whether the pet seems to be uncomfortable when he or she urinates
- Whether the pet shows any signs of nervous system disease such as weakness or seizures
Blood tests may be performed to look for evidence of kidney damage from infection or for the presence of diseases that might lead to increased urine production.
Plain and/or dye X-rays or ultrasound may be performed to look at the parts of the urinary tract.
Treating the Incontinent Patient
Specific treatment of an underlying disease may resolve incontinence; for example, surgery to correct an ectopic ureter. Inappropriate urination caused by behavioral problems may be corrected with training that modifies the pets behavior.
When no specific cause can be identified for the incontinence drugs may be given that increase the tone of the muscles that hold urine in the bladder. Some drugs that are used for this purpose include estrogen, ephedrine and phenylpropanolamine. Phenylpropanolamine is a sympathomimetic, non-hormonal agent which increases sphincter tone and alleviates urinary incontinence by stimulation of the alpha adrenergic receptors in the urethral muscle.
Drug therapy for incontinence may be based on trial of different drugs in various doses. Since some of these drugs can have side effects so low doses are tried first. Some drugs may be slow to have an effect so as long as there are no undesirable side effects, a drug trial should continue for several weeks before the drug is considered not to be effective.