Dog: Prostate Enlargement

General information

Other common/scientific names: prostatomegaly, benign prostatic hyperplasia (BPH), prostatitis, prostatic abscess, prostatic cysts, prostate cancer

The prostate is considered an accessory sex gland. It is a bi-lobed structure that lies just behind the bladder and under the colon, surrounding the urethra (the tube which carries urine from the bladder). The prostate produces fluid which both nourishes and gives volume to the sperm. This fluid enters the urethra as it courses through the prostate gland. Sperm cells from the testicles mix with the prostatic fluid in the urethra. The urethra then carries the semen through the penis during ejaculation.

The prostate gland starts to develop before the male dog reaches puberty. Testosterone, produced in the testicles, is responsible for the growth of the prostate. It attains its maximum size by about two years of age. Due to the lack of testicles and thus testosterone, dogs that are castrated before puberty have very small prostate glands.


Prostate enlargement or prostatomegaly is common in the intact (non-castrated) male dog. Causes of prostate enlargement include:

  • Benign prostatic hyperplasia (BPH): In the dog, this is the most common prostatic disease. It is caused by the normal aging process where the glandular tissue hypertrophies or grows in size.
  • Prostatitis: Prostatitis is inflammation of the prostate gland, usually caused from a bacterial infection.
  • Prostatic abscess: A prostatic abscess is a walled off pocket of infection containing white blood cells, bacteria and cellular debris (pus).
  • Prostatic cysts: Prostatic cysts are fluid-filled sacs from within or adjacent to the prostate. These can result from hormone changes or abnormal development of the prostatic tissue. Most prostatic cysts are asymptomatic; however, they can become large, painful and infected.
  • Prostate cancer : Prostate cancer is rare in dogs but it is usually malignant and life-threatening.


Bacteria can travel to the prostate via the bloodstream or from the urinary tract. Because the urethra travels through the prostate, bacteria can invade the prostate from the bladder or from the penis. Conversely, an infected prostate can continuously seed the bladder with bacteria causing repeated urinary tract infections.

Cardinal symptom

Painful urination


Dogs with benign hyperplasia may be asymptomatic. However, an enlarged prostate may cause signs of straining and pain to urinate and defecate. Dogs with painful prostates will walk stiffly. With prostatitis, bloody or pus-filled urine and a fever may be seen. In cases of prostate cancer, weight loss, lack of appetite and lethargy are usually evident.


All mature dogs should have a prostatic examination annually. This is performed by your veterinarian inserting a gloved finger in the rectum and palpating (feeling) the prostate. A castrated male should have a small prostate. If prostate enlargement is diagnosed and clinical signs are present, further testing is needed to determine a cause. A complete blood count (CBC) and serum biochemistry profile is performed to assess organ function. A urine sample taken by a catheter will contain cells from the prostate. These samples are examined with a microscope for evidence of infection, inflammation or cancer. Radiographs and ultrasonography of the prostate can be used to better assess the size and consistency of the prostate and surrounding organs. A fine needle aspirate or biopsy may be needed to confirm a diagnosis.


Treatment of prostate enlargement will depend on the cause. Dogs showing clinical signs with benign prostatic hyperplasia can be treated with surgical castration. Bacterial prostatitis is treated with antibiotics and analgesics. Severe cases may require hospitalization with intravenous fluids, antibiotics and analgesics. Surgical drainage is indicated for dogs with a prostatic abscess or large prostatic cyst. Radiation can be used for pain relief in dogs with prostate cancer.


The prognosis of prostate enlargement will depend on the cause and extent of disease. Benign prostatic hyperplasia usually responds well to surgical castration. Prostatitis can be difficult to treat and result in chronic, debilitating infections. Prostate cancer usually spreads to other parts of the body and carries a grave prognosis.


Over 90% of prostate enlargement can be prevented by castrating the dog within the first year of life. Castration will not prevent prostate cancer.

Update version: 4/24/2014, © Copyright by
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