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Wednesday, 26 September 2012 00:59
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Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .


Dr Liesel van der Merwe

I was preparing for a talk on incontinence and came upon a statement that dogs are the only species to share the urinary problems experienced by humans as they age. They are, in fact, often used as experimental models to test drugs.

Sterilised bitches are inclined to develop urinary incontinence in the same way as menopausal women, and uncastrated male dogs are prone to an enlarged prostate and difficulty in passing urine, as occurs in older men. 

Incontinence is the leakage of urine when the dog is lying down or standing or sleeping. Urine leakage is more common in female dogs because the urethra (tube from the bladder) is short and wide. The long urethra in male dogs results in natural resistance, regardless of whether the urethral are properly toned.

Anatomical causes for incontinence usually manifest in young animals. Ectopic ureters occur when the tubes from the kidneys bypass the bladder and open into the bladder neck, urethra or even the vagina. Urine is then not stored properly but leaks out as it is being produced by the kidney.

The dogs’ position and activity will determine when they leak. The normal bladder neck is lower than the pelvis, so a dog may not leak while standing, but will when lying or jumping.

The bladder is a muscular sac with many nerve and hormone receptors which finely tune the whole urination reflex. The sac is closed off by the urethral sphincter, a muscular band which also has a host of nerves and hormone receptors which affect its tone. In sterilised bitches the lack of oestrogen can cause the muscle tone to decrease and urine leakage to occur.

Dogs which leak are more prone to infections as the low tone also allows retrograde movement of urine, which may flush bugs into the bladder. The bladder is normally sterile but towards the urethral opening there are normal commensal bacteria. An infection makes the leakage worse, as the bladder is irritated and contracts more.

Treatment is aimed at supplementing hormones to improve sphincter tone. These medications are often only partially effective and sometimes surgical options, such as pulling the bladder deeper into the abdomen, placing a tape suture around the urethras to narrow it or injecting collage into the urethra near the bladder to narrow it, are recommended. All these techniques have their good and bad points and most are effective, at least for one to two years, or improve control combined with the medication.

Even though incontinence may be a consequence of sterilisation, there are positive aspects to sterilisation. Early sterilisation (before the second heat) significantly reduces a bitch’s risk of breast cancer. Intact bitches, which are not bred, are prone to developing uterine infections that can cause severe illness.

In the male dog the problem is exactly the opposite. Due to enlargement of the prostate in uncastrated dogs, they struggle to urinate. In dogs the prostate encircles the urethra just after it leaves the bladder. As the prostate enlarges it may compress the urethra or it may cause muscular spasms which make urination difficult.

In the majority of these dogs castration and the resultant shrinkage of the prostate due to lack of testosterone will solve the problem. In a small percentage of cases, even in dogs which were castrated as young animals, the synchronicity of the urination process is a problem and medication causing urethral relaxation is required. Uncastrated dogs are also inclined to develop prostatic cysts which can become infected. This can cause severe bacterial septicaemia and is a serious disease.

When you decide on sterilising or not sterilising your dog, bear all these advantages and disadvantages in mind. If your dog is incontinent, don’t think it is just part of the ageing process. We can try to manage the condition, especially for dogs that live indoors. 

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