Dog - Prostatic Disease

What is the prostate gland?

The prostate gland is located next to the neck of the urinary bladder in the male dog. The urethra passes through it on its way from the bladder, via the penis, to the exterior. The gland produces some of the fluids found in normal canine semen.

What are the signs of prostatic disease?

1. Enlargement of the gland is common with most prostatic diseases.
2. Enlargement of the prostate constricts the part of the urethra passing through it so that difficulty in urination is often the first sign noticed by owners.
3. Urethral obstruction rarely occurs, but affected dogs will spend considerable time trying to urinate and only pass a small quantity of urine.
4. Since the colon, prior to joining the rectum, is located just above the prostate, an enlarged prostate often results in pressure on the colon and undue and often unproductive straining to pass faeces will frequently be noted.
5. Blood is frequently seen both in the urine and on voided faeces as a result of this straining. Since prostatic problems involve bacterial infection, haematuria (blood in the urine) may also indicate bacterial inflammation of the bladder (cystitis).

What are the problems that cause the prostate to enlarge?

There are several conditions that can be responsible:

1. Benign prostatic hyperplasia. This is benign (non-cancerous) enlargement of the prostate. Associated with the hormone testosterone it is a very common problem.
2. Squamous metaplasia. This is a similar benign problem but caused by excess amounts of a different hormone (oestrogen).
3. Cystic hyperplasia. This is usually secondary to either 1 or 2 (above). It is caused by obstruction of the ducts that carry the prostatic secretions to the urethra. As a result multiple, fluid-filled cavities are formed within the gland.
4. Paraprostatic cysts. These are fluid-filled cysts which frequently form in tissue left behind during embryonic development. Although often present from birth they frequently are not detected until the dog is middle aged or older.
5. Bacterial infection. This is usually secondary to another prostatic abnormality, e.g. cystic hyperplasia. Infection can gain access to the prostate via the urethra, either from the environment or descending from the bladder should any previously undiagnosed cystitis be present.
6. Prostatic abscess. This is the next stage from bacterial infection. If drainage from the prostate is obstructed and infection is present, an abscess is likely to form.
7. Prostatic cancer. THIS IS NOT COMMON IN THE DOG. It may be associated with certain hormone imbalances.

How are these conditions diagnosed?

The first step is to ascertain the size of the prostate. This can be estimated by palpating (feeling) the prostate through the abdominal wall or by rectal examination during which a gloved finger is introduced into the rectum. It can then be confirmed by diagnostic imaging (x-rays or ultrasound scan).

Because there are so many problems that can cause enlargement of the gland it is then necessary to carry out various laboratory tests in order to reach a diagnosis. These include examination of the dog's urine and examination of the prostatic secretion. Biopsy samples may sometimes have to be taken if more simply obtained samples, e.g. urine, yield no positive results. Individual diagnostic work up will be fully discussed with you.

How is prostatic disease treated?

1. Diseases involving bacterial infections are treated with appropriate antibiotic therapy. Often this treatment may be necessary for weeks rather than days. As previously mentioned prostatic infection is usually secondary to other underlying problems.
2. Diseases associated with excessive hormone, e.g. benign prostatic hyperplasia or cystic hyperplasia often respond well to neutering since the hormones involved are produced within the testes. Following castration, within a month, the prostate often returns to its normal size.
3. Paraprostatic cysts and prostatic abscesses usually require major surgery.
4. As mentioned some prostatic tumours may respond to hormone therapy. Unfortunately if the primary prostatic tumour is one of the low percentage that are malignant, it is likely to have already metastasised (spread) to other parts of the body before diagnosis is made.