Urinary Incontinence in the Dog

1 06 2011

Urinary Incontinence in the Dog

 

 

 

Think collagen injections will take our wrinkles?  Collagen injections can do that and more.  Veterinary Surgeons have found that collagen injections placed beneath the surface of the urethra may help with urinary incontinence especially in spayed female dogs (those dogs having undergone an ovarian hysterectomy surgery).

 

For the last 40 years it has been known that up to 20% of spayed female dogs may develop urinary incontinence following removal of their ovaries.  It has been found that the urethral closure pressure is significantly reduced within one year of being spayed.  This type of incontinence is termed urethral sphincter mechanism incompetence or USMI.  Larger breed of dogs such as the boxer, giant schnauzer, Doberman and Rottweiler seem to be at an increased risk for developing this type of incontinence.

 

In female dogs the incontinence typically occurs when the dog is asleep and their bed area will be wet upon wakening. Male dogs may also be affected, however they are much less frequently affected than are female dogs and there appears to be no correlation with neutering (castration).  Male dogs tend to be incontinent when they are awake in contrast to females which are typically incontinent when asleep. Male dogs tend to become incontinent at an advanced age, while female dogs tend to be younger and have a history of incontinence immediately or shortly after having undergone an ovariohysterectomy.

 

USMI may be directly proven by a urethral pressure profile for which special equipment is necessary and will probably necessitate referral to a specialist.  In most cases USMI is diagnosed by ruling out the other causes of abnormal elimination. If you suspect your dog may have USMI, your veterinarian will be able to distinguish this type of incontinence as compared to other reasons for inappropriate elimination of urine through the history of the incontinence as well as the use of some common laboratory tests.

 

Congenital malformations of the bladder and ureters typically cause urinary incontinence in only in extremely young animals. Contrast imaging may be used to confirm a diagnosis in the young pet that has a history of incontinence since it was a puppy.

 

Bacterial cystitis or bladder infection is a common cause for frequent urination. A female dog may squat frequently and will typically eliminate only small amounts of urine since the elimination of urine is painful.  Remember with cystitis the dog will have control of when to urinate and will adopt a typical stance to urinate, while with USMI the loss of urine is involuntary (not under the dog’s control).  A urinalysis will quickly distinguish between these two syndromes.

 

Diseases that cause increased thirst and urination may sometimes be confused with USMI.  These diseases cause a net increase in fluid intake and thereby urine production.  Diseases such as kidney problems, Dibetes Mellitis and Cushings may all cause a dilute urine resulting in the dog urinating frequently with large amounts of urine.  These diseases may be ruled in or out through the use of a blood test.

 

When other possible problems have been eliminated, and the dog has a history of being spayed recently and the incontinence is deemed involuntary then medical treatment for USMI should be started. With USMI medical treatment (treatment with drugs affecting the urethra) is still the treatment of choice and should be tried before proceeding to surgery.  Drugs useful in treatment include α-adrenergic agonists such as phenylpropanolamine or pseudoephedrine.   Alpha-adrenergic agonists increase urethral closure pressure which may result in continence in at least 75% of USMI cases in female dogs but is unfortunately less than 50% successful in male cases of USMI.  Phenylpropanolamine appears to be more effective than pseudoephedrine.  These α-adrenergic substances are contraindicated when the dog has renal insufficiency, cardiac arrhythmias, glaucoma or is hypertonia.

 

Short-acting estrogens or conjugated estrogens may also be used in the medical treatment of USMI, but only in spayed female dogs.  Unfortunately, estrogens may cause unwanted side effects, such as swelling of the vulva and may cause the female dog to be attractive to male dogs.  The long acting injectable estrogens are not longer used because they may result in bone marrow depression leading to a non-regenerative anemia.

 

Surgery should be considered when a dog does not respond to medication alone or in combination, when there are side effects from the medication or if the medication is contraindicated.  When regular administration of the medication is not possible surgery may also be an alternative.

 

Three different surgeries are available to correct incontinence due to USMI with a success rate of 50 to 75%. The three surgeries are colposuspension, urethropexy and endoscopic injections of collagen.  Endoscopic injections of collagen being the least invasive of the surgical possibilities in the female dog.

 

Collagen is injected under general anesthesia and three collagen deposits are injected beneath the urethra.  With a female dog this is done with a cystoscope which is introduced through the urethra.  In the male the procedure is more involved requiring both a laparatomy (surgical access through the abdomen, in this case to grant access to the bladder) and cystotomy (surgery through the bladder wall).  The injection of collagen will also increase the risk for prostatitis (inflammation of the prostrate) and therefore male dogs should be castrated 3 weeks before undergoing the procedure.

 

When using collagen injections the initial result may deteriorate within the first 12 months.  If and when incontinence recurs, the collagen injection may be repeated or medical therapy may be reinstated.  Response to medical therapy may be better following collagen injections even when the medical therapy was unsatisfactory before surgery.

 

 

 

References:

 

Arnold, Susi, DVM, Hubler, Madeleine, et all.  “Collagen Injections”.  NAVC Clinician’s Brief. November 2007.  Pp. 43-44.

 

 

 

 

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