Disease and Illnesses of dogs – Urinary incontinence in bitches

What is urinary incontinence and what causes it?

Urinary incontinence is when your pet is leaking urine involuntarily. This happens most often when they are lying down and you may see a wet patch on the bed when they get up from resting. Occasionally urine can be dripping when they are walking along as well but animals with urinary incontinence will be able to urinate normally whilst out on a walk too. Animals with urinary incontinence can lick at their back end frequently to keep themselves clean and will also often drink more (polydipsia) to compensate for loosing fluids via the urine.

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Urine is normally held within the bladder by two muscular sphincters called the internal and external urethral sphincters. Urinary incontinence occurs when, for a variety of reasons those sphincters become weak and allow the urine to leak out. These reasons can include anatomical defects in the urinary tract, sometimes present from birth and this causes urinary incontinence in young animals. Any generalised nerve problem or disease causing muscle weakness can affect the urinary sphincters in addition to the other muscles in the body. Age can also weaken the muscles of the sphincters so urinary incontinence is often seen in older dogs.

Urinary incontinence is seen far more commonly in female dogs than in male dogs and this is because the main mechanism that causes incontinence is related to spaying. The female sex hormone, oestrogen plays a part in keeping the sphincters tight and therefore retaining urine in the bladder. After a bitch has been neutered, levels of oestrogen are lower and this can lead to “Sphincter Mechanism Incompetence” or SMI which is the most common cause of urinary incontinence in female dogs. Urinary incontinence is however able to be managed with medications as discussed below so the potential for developing SMI does not outweigh the benefits of neutering.

How is Urinary Incontinence diagnosed?

Urinary incontinence is mainly diagnosed from the history and clinical signs of involuntary leaking of urine. Often a urine sample will be assessed to check for any signs of a urinary tract infection that may be compounding the problem. Blood tests may also be recommended to check kidney function and to screen for diseases that may be causing an increased thirst which will again worsen the urinary incontinence.

In cases of urinary incontinence in younger animals where an anatomical deformity of the urinary tract is suspected then imaging of the urinary tract may also be advised. This may include ultrasound scans and x-rays of the urinary tract.

How is urinary incontinence treated?

Propalin

This is a liquid medication that is given orally three times a day. The volume of liquid given is dependent on the weight of your dog. The active ingredient is phenylpropanolamine. The branch of the nervous system that is involved in retaining urine in the bladder is the sympathetic nervous system and phenylpropanolamine is a sympathomimetic which means it mimics the nerves of the sympathetic nervous system, causing the muscular sphincters to tighten and stop the leaking of urine. Propalin can have some side effects such as diarrhoea and a raised heart rate and blood pressure.

Incurin

This is a medication in the form of a tablet. Dogs with urinary incontinence are given one tablet daily, regardless of their size. If this is not successful then the dose can be doubled. Incurin contains Estriol which is an oestrogen. It works by increasing the oestrogen levels which have been lowered by neutering which tightens the urethral sphincters and stops the leaking of urine. As a result of this mechanism of action, Estriol has only been shown to work in female dogs that have been neutered.

In some cases of urinary incontinence there are surgical options for treatment. When there are anatomical problems with the urinary tract and it has not formed correctly, these defects can be corrected surgically. The most common defect is ectopic ureters where the tubes that lead from the kidneys to the bladder are not positioned correctly on the bladder. These can be repositioned surgically to help rectify the incontinence.


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