The canine bladder: vulnerable: you need to understand the serious disorders that can impair your dog's ability to urinate normally.
Urinary Incontinence. A high percentage of canine bladder-related problems are marked by urinary incontinence, a condition that Richard Goldstein, DVM, an associate professor of small animal medicine at Cornell University's College of Veterinary Medicine, characterizes as "a storage or leaky-outlet problem."
"Incontinence starts with the bladder, which holds the urine until it is released from the dog's body," he says, "and usually involves the urethral sphincters, which make up the urethra's closure system."
There are two kinds of urethral sphincters, rings of elastic tissue that tighten or loosen as needed in order to, respectively, prevent or allow the flow of urine from the bladder. One of the sphincters is inside the tube and functions automatically to restrict the flow. The other sphincter is external and is closed at all times when a dog is awake and is not about to urinate. Urination requires conscious coordination to open the two urethral sphincters, a process in which the bladder must participate.
"The bladder has to be relaxed when the sphincters are closed," says Dr. Goldstein, "and any lack of compliance in that regard--any hypercontraction of the bladder--can also lead to incontinence."
Incontinence is usually manifested in the unconscious release of urine during the storage phase, often when a dog is lying down, whether resting or fast asleep. It may occur either continuously or intermittently, and the volume may vary, depending on the underlying cause and its severity.
Possible Problems. The cause or causes of incontinence may be neurogenic. That is, the condition may result from abnormalities of the parts of the spinal cord and nervous system associated with the regulation of urine--its storage within the bladder and its flow from the organ. The condition may be precipitated by, for example, age-related degeneration of the spinal nerves in older dogs, or even from traumatic injury to the spinal cord in animals of any age.
Most canine bladder disorders, however, are not caused by a nervous system malfunction. And although neurogenic disorders often cause incontinence, they can also result in other problems, such as difficulty in urinating, blood in the urine, or, worst case, a complete and life-threatening blockage of the urethra or ureters.
Far more frequently diagnosed non-neurogenic conditions include a weak internal urethral sphincter, bladder inflammation (cystitis); the formation of stones in the urinary tract (urolithiasis); and the development of benign or cancerous growths (neoplasms) in the tissue lining the bladder.
Cystitis--Inflammation of the canine bladder can be caused by the presence of stones in the organ or, less frequently, a benign or cancerous tissue invasion of the bladder wall. The most common cause by far, however, is a bacterial infection that either originates in the bladder or spreads there from another area of an animal's body.
"If the bladder becomes infected," Dr. Goldstein explains, "it can become very sensitive and tend to contract. And this can cause leakage as well as a sense of urinary urgency, even when only a small volume of urine is in the bladder.
Bacterial Infection--This can also cause a burning sensation in the urethra and make a dog constantly experience pain while urinating. "When a dog presents with incontinence," notes Dr. Goldstein, "bacterial infection is one of the first things that a veterinarian looks for."
Fortunately, he notes, cystitis can almost always be treated successfully with oral antibiotics, once the specific bacterium responsible for the infection is identified.
Urolithiasis--Although stones (uroliths) may form anywhere in the urinary tract, they are almost always found in the bladder. These stones are composed primarily of inorganic materials--most commonly minerals such as struvite or calcium oxate, although other types of stones may develop in certain canine breeds.
In advanced cases, a small urolith can pass from an animal's bladder into its urethra and interfere with the passage of urine. A complete blockage of the urethra--one that totally obstructs the flow of urine and prevents the elimination of poisonous wastes from a dog's system--will constitute a potentially fatal medical emergency for which immediate veterinary care, possibly entailing surgery, is required.
Neoplasms--A variety of abnormal growths, some of minor concern and others that are apt to have fatal consequences, can originate in the canine urinary system. Among all components of this system, it is the bladder and urethra that are most often affected by cancer--most frequently a malignant tumor known as transitional cell carcinoma. This cancer originates in the cells lining the interior cavity (lumen) of the bladder or urethra and subsequently grow into the cavity, forming a mass that, in some cases, may become dangerously large. From there, the deadly cancer may spread to other areas of the body.
Because the major clinical signs of canine bladder cancer (blood in the urine, straining to urinate, and frequent urination) are the same as the signs of other bladder disorders, the diagnosis may be definitively diagnosed only through specialized testing--ultrasound imaging, for example.
By that time, unfortunately, the disease may have reached an advanced stage, and an affected dog's survival will depend on the type of cancer, its location within the bladder, its rate of growth, and the extent to which it may have invaded other tissues by the time it is diagnosed.
DON'T DELAY. You should immediately report to your veterinarian any changes in your dog's excretory patterns.
RELATED ARTICLE: EARLY DIAGNOSIS: VERY IMPORTANT TO YOUR DOG'S HEALTH
Dr. Richard Goldstein points out that the success with which any canine bladder disorder is treated will depend largely on the stage at which it is diagnosed. He advises owners, therefore, to report without delay any changes in a dog's excretory patterns, the frequency of urination, or the color of its urine.
Indications that something may be wrong--perhaps terribly wrong--with your dog's bladder include noticeably frequent urination; urine leakage while lying down or walking; apparent pain or difficulty urinating; or blood in its urine. An affected dog may also appear weak and depressed, show a decline in appetite, and lose weight.
Veterinary diagnosis will include a thorough physical exam, complete blood count and blood chemistry profile, urinalysis, and possibly X-rays, ultrasound or other imaging procedures. The object, says Dr. Goldstein, is to establish the cause of an apparent bladder-related disorder--bacterial infection, say, or the presence of uroliths in the urinary tract as early as possible.
The veterinarian is also likely to observe the way in which the dog moves around, since stumbling or any other gait abnormality could suggest the presence of an underlying neurologic disorder.
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|Date:||Sep 1, 2011|
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