Prostate Enlargement in Dogs

PetMD Editorial
By PetMD Editorial on Nov. 17, 2008
Prostate Enlargement in Dogs

Prostatomegaly in Dogs

Prostatomegaly is a medical condition in which the prostate gland is abnormally large. This is determined by rectal or abdominal palpation, or by abdominal X-ray or ultrasound imaging of the prostate. The enlargement can be symmetrical or asymmetrical, painful or nonpainful. Normal prostate size varies with age, body size, castration status, and breed, so determination of the enlargement is subjective.

Enlargement of the prostate gland can result from the proliferation or enlargement of epithelial cell (cells that line the cavities and surfaces of structures throughout the body); pre-cancerous cells in the prostate; or from inflammatory cell infiltration (e.g., acute and chronic bacterial prostatitis and prostatic abscess). Prostatomegaly is typically noted in middle-aged to older male dogs.

Symptoms and Types

  • Asymptomatic (without symptoms)
  • Straining to defecate/constipation
  • Ribbonlike stools
  • Difficulty urinating


  • Benign (harmless) prostatic enlargement
  • Squamous metaplasia: benign changes in the linings of the prostate
  • Adenocarcinoma: cancer that originates in glandular tissue
  • Transitional cell carcinoma: tumor of the urinary bladder
  • Sarcoma: cancer of the connective or supportive tissue (bone, cartilage, fat, muscle, blood vessels) and soft tissue
  • Cancer that metastasizes (spreads)
  • Acute bacterial prostatitis (inflammation)
  • Chronic bacterial prostatitis
  • Prostatic abscess
  • Prostatic cyst
  • Risk Factors
  • Castration lowers the risk of benign prostatic enlargement and bacterial prostatitis
  • Risk of prostatic adenocarcinoma is, however, increased three-fold in castrated dogs


Since there are several possible causes for this condition, there also several different avenues your veterinarian can take in making the diagnosis. The diagnostic tools your veterinarian chooses will be based on the initial physical examination. Ultrasound is usually the tool of choice in determining whether the prostate is enlarged and whether there are cysts or abscesses on the prostate. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, and a urinalysis to determine whether an infection, bacterial or other, is involved. White blood cells in the urine, or in the seminal fluid, meanwhile, would indicate an infection of the bladder or urinary tract.

An examination of prostatic fluid obtained by ejaculation or prostatic massage may provide additional information about the state of the blood and whether an infection is present. Ultrasound will be used as a visual aid for guiding a fine-needle to the prostrate in order to draw fluid and/or cell tissue for biopsy. This process is referred to as fine needle aspiration.


The course of treatment your veterinarian prescribes will vary with the underlying cause of the prostatomegaly. Surgical castration is indicated in symptomatic dogs with benign enlargement. Acute (sudden and severe) infection, with bacterial prostatitis (inflammation of the prostate gland), will usually be resolved with antimicrobial medication.

Surgical drainage is indicated for dogs with prostatic abscess or large prostatic cysts.

External beam radiotherapy may provide relief of pain in patients with prostatic carcinoma. The medications your veterinarian prescribes will be suited to the specific needs of your dog.

Living and Management

Your veterinarian will want to perform additional abdominal radiographs or prostatic ultrasonography to assess whether the treatments are working and progress is being made. Urine and prostatic fluid cultures will also be conducted to assess whether the antimicrobial treatment is working in patients with bacterial prostatitis.

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