section name header

Basics ⬇

Basics

Definition

Abnormally large prostate gland determined by rectal or abdominal palpation or by abdominal radiography or prostatic ultrasonography. The enlargement can be symmetrical or asymmetrical, painful or non-painful. Normal prostate size varies with age, body size, castration status, and breed so assessment of enlargement is subjective.

Pathophysiology

Enlargement can result from epithelial cell hyperplasia or hypertrophy (e.g., benign prostatic hyperplasia), neoplasia of prostatic epithelium or stroma, cystic change within the prostatic parenchyma, or inflammatory cell infiltration (e.g., acute and chronic bacterial prostatitis and prostatic abscess).

Systems Affected

  • Urinary
  • Reproductive

Signalment

  • Dog
  • Typically occurs in middle-aged to older males

Signs

  • May be none
  • Straining to defecate
  • Ribbon-like stools
  • Dysuria
  • Urethral outflow obstruction

Causes

  • Benign prostatic hyperplasia
  • Squamous metaplasia
  • Adenocarcinoma
  • Transitional cell carcinoma
  • Sarcoma
  • Metastatic neoplasia
  • Acute bacterial prostatitis
  • Prostatic abscess
  • Chronic bacterial prostatitis
  • Prostatic cyst

Risk Factors

  • Castration lowers the risk of benign prostatic hyperplasia and bacterial prostatitis.
  • Risk of adenocarcinoma may be increased three-fold in castrated dogs.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Benign prostatic hyperplasia-typically causes non-painful symmetrical enlargement of the prostate gland; not found in neutered dogs.
  • Primary or metastatic neoplasia-typically causes painful, non-symmetric enlargement of the prostate gland; weight loss, impaired appetite, rear limb weakness observed in some patients; suspect neoplasia in castrated dogs.
  • Acute bacterial prostatitis-typically results in slight-to-moderate symmetric or non-symmetric enlargement of the prostate gland with prostatic pain. Fever, impaired appetite, rear limb weakness, and painful abdomen observed in some patients.
  • Chronic bacterial prostatitis-signs similar to those seen in dogs with acute prostatitis or those related to recurrent lower urinary tract infection (e.g., dysuria and hematuria). Systemic signs less common than in acute bacterial prostatitis; bacterial prostatitis uncommon in castrated dogs.
  • Prostatic abscess-may result in signs similar to those in patients with acute or chronic prostatitis; abscess rupture causes fever and caudal abdominal pain.
  • Prostatic cysts-may be associated with palpable caudal abdominal mass, straining to urinate, or straining to defecate; patient may also be asymptomatic.

CBC/Biochemistry/Urinalysis

  • CBC normal in patients with benign prostatic hyperplasia.
  • Leukocytosis in patients with acute and chronic (occasionally) bacterial prostatitis, prostatic abscess, and prostatic neoplasia (occasionally).
  • High bilirubin and alkaline phosphatase in some patients with prostatic abscess.
  • Urinalysis-may be normal.
  • Hematuria in patients with benign prostatic hyperplasia.
  • Pyuria, hematuria, proteinuria, and bacteriuria in patients with bacterial prostatitis.
  • Pyuria, hematuria, proteinuria, and, occasionally, neoplastic cells in dogs with prostatic neoplasia.

Other Laboratory Tests

Serum prostatic esterase concentration may be high in dogs with benign prostatic hyperplasia.

Imaging

Radiographic Findings

Prostatomegaly

Ultrasonographic Findings

  • Abscess or cyst-hypoechoic or anechoic lesions with distal enhancement.
  • Acute bacterial prostatitis-uniform prostatic echogenicity.
  • Benign prostatic hyperplasia-uniform prostatic echogenicity; small fluid-filled cysts in some patients.
  • Chronic bacterial prostatitis-focal or diffuse hyperechogenicity.
  • Prostatic neoplasia-focal to multifocal areas of coalescing echogenicity and acoustic shadowing (if dystrophic mineralization occurs).

Diagnostic Procedures

  • Examination of prostatic fluid obtained by ejaculation or prostatic massage may reveal changes similar to those seen on urinalysis.
  • Bacterial culture of prostatic fluid typically reveals >100,000 CFU of bacteria/mL in dogs with bacterial prostatitis.
  • Needle biopsy of the prostate with ultrasound guidance provides visualization of the area to be sampled and increases the likelihood of obtaining a diagnostic sample; take care to avoid iatrogenic rupture of a prostatic abscess.

Treatment ⬆ ⬇

Treatment

Medications ⬆ ⬇

Medications

Drug(s) Of Choice

Benign Prostatic Hyperplasia

Bacterial Prostatitis

Choose antibiotics on the basis of antibacterial susceptibility testing of the isolated pathogen and ability of the antibiotic to diffuse into prostatic fluid in therapeutic concentrations. Good choices for the latter include trimethoprim-sulfa, chloramphenicol, and fluoroquinolones.

Prostatic Carcinoma

Chemotherapy has not been proven beneficial.

Precautions

Long-term administration of megestrol acetate or medroxyprogesterone can cause diabetes mellitus.

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

  • Abdominal radiographs or prostatic ultrasonography to assess efficacy of treatment in benign prostatic hyperplasia, prostatic carcinoma, or bacterial prostatitis.
  • Urine and prostatic fluid culture to access efficacy of treatment in patients with bacterial prostatitis.

Possible Complications

  • Urethral obstruction
  • Rectal obstruction

Miscellaneous ⬆

Miscellaneous

See Also

Authors Carl A. Osborne and Jeffrey S. Klausner

Consulting Editor Carl A. Osborne

Acknowledgment The authors and editors would like to acknowledge the prior contribution of Margaret V. Root Kustritz.

Suggested Reading

Smith J. Canine prostatic disease: A review of anatomy, pathology, diagnosis, and treatment. Theriogenology 2008, 70:375–383.