Contributors: Autumn P Davidson

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Benign hypertrophy Prostate: benign hyperplasia and hypertrophy is most common prostatic disease.
  • Other diseases:
  • Signs: depends on etiology - can include: urethral discharge, pyrexia, abdominal pain, hematuria, weight loss, dysuria.
  • Treatment: castration, anti-androgens, antibiotics, surgery.
  • Prognosis: good to poor.
Follow the diagnostic tree for Penile discharge in dogs Penile discharge in dogs.

Presenting Signs

  • Asymptomatic.
  • Tenesmus (especially on defecation).
  • Urethral discharge (hemorrhagic or purulent) unassociated with urination.
  • Caudal abdominal pain, reluctance to move (acute bacterial prostatitis).
  • Hematuria.
  • Weight loss.
  • Dysuria/urine retention.
  • Change in semen quality, hemospermia.

Acute Presentation

  • Acute peritonitis, bacteremia, septic shock (acute bacterial prostatitis).

Age Predisposition

  • >3 years (incidence increases with age).
  • >10 years (neoplasia).

Breed Predisposition

  • No breed predilection.

Special Risks

  • Prostatic massage: contraindicated bacterial prostatitis because may → bacteremia.

Pathogenesis

Etiology

  • Older dogs → altered androgen/estrogen ratio → benign prostatic hyperplasia, prostatic cysts (ductal occlusion or prostatic oversecretion) or bacterial prostatitis.
  • Paraprostatic cyst occasionally originates from a uterus masculinus, in which case there is no direct connection between cyst and prostate.
  • Urinary tract infection → prostatic infection.
  • Prostatic squamous metaplasia develops due to an increased [estrogen] level, eg due to Sertoli cell tumor or iatrogenic.

Predisposing Factors

General
  • Intact male.
  • age.

Specific

  • Uncastrated male animal (benign prostatic hyperplasia).
  • Urinary tract infection (prostatic infection).

Pathophysiology

  • Disease → enlarged prostate → pressure on ventral rectum → partial fecal obstruction and tenesmus.
  • If disease → involves prostatic urethra → difficulty or inability to urinate, most likely associated with neoplasia.
  • Bacterial infections may → bacteremia → septic shock.
  • Malignant neoplasms (5% of prostatic disease) → metastasize to sublumbar lymph nodes or lung.

Diagnosis

Presenting Problems

  • Fecal tenesmus.
  • Reluctance to breed.
  • Urethral discharge.
  • Pyrexia.

Client History

  • Fecal tenesmus.
  • Urethral discharge unassociated with urination.
  • Hematuria.
  • Hemospermia.
  • Weight loss.
  • Abdominal pain/reluctance to move.
  • Dysuria/urinary retention.

Clinical Signs


Rectal examination
  • If prostate is enlarged, it lies cranial to the pelvic inlet.
  • Bilateral, symmetrically enlarged, non-painful prostate in benign prostatic hyperplasia. The median raphe is still palpable.
  • Bilateral, symmetrically enlarged, painful prostate in acute bacterial prostatitis. Loss of the median raphe.
  • Asymmetrically enlarged, smooth even surface on palpation in prostatic or periprostatic cyst.
  • In chronic bacterial prostatitis the prostate is sometimes enlarged, asymmetrical, hard and non-painful on palpation.
  • Asymmetrically enlarged, irregular, often painful in prostatic neoplastic disease.

Other findings
  • Caudal abdominal mass on palpation.
  • Pyrexia.
  • Weight loss.
  • Urethral discharge.

Diagnostic Investigation


Radiography
  • Lateral abdominal radiographs Radiography: abdomen prostatic enlargement pushing the colon/rectum dorsally.

    Contrast medium in bladder will help to distinguish bladder from prostate.
  • Acute periosteal new bone formation on the cranial brim of the os pubis and ilia or on the lumbar vertebrae Prostate neoplasia (bone changes) - radiograph lateral.
  • Localized peritonitis.
  • Thoracic radiographs Radiography: thorax indicated to rule out pulmonary metastases.
Contrast Radiography2-D Ultrasonography
  • Symmetrical enlargement, no change in echotexture in benign prostatic hyperplasia and mildly hyperechoic in bacterial prostatitis.
  • Asymmetrical enlargement, mixed echogenicity in prostatic neoplasia or some chronic cases of bacterial prostatis.
  • Asymmetrical enlargement, hyperechoic with hyperechoic sediment in prostatic abscess.
  • Thin walled hypoechoic areas within or connected to the prostate in prostatic or periprostatic cysts.
  • Combined disease possible.

UrinalysisCytopathology
  • Prostatic wash.


    Contraindicated if dog pyrexic and leukocytic.
  • See prostatic wash Cytology: prostatic wash for technique.
  • Culture may be positive (bacterial prostatitis), similar infections to urinary tract infection.
  • Neutrophil degeneration (prostatic abscess).
  • Semen analysis with fractionation prostatic fluid.
  • Cystic fluid (prostatic cyst).
  • Ultrasound-guided fine needle aspirate or biopsy.
  • Neoplastic cells (prostatic neoplasia).
Hematology
  • Leukocytosis, left shift in severe prostatic infections or leukopenia in some cases.
Biochemistry
  • Increased liver enzymes (endotoxemia).
Histopatholgy
  • Biopsy or fine needle aspiration.
  • Benign prostatic hypertrophy.
  • Prostatitis/abscess.
  • Prostatic neoplasia.

Gross Autopsy Findings

  • Abnormalities of prostate depend on underlying disease process.
  • Metastases (sublumbar lymph nodes, lung).
  • Localized peritonitis.
  • Perineal hernia.

Differential Diagnosis

  • Causes of caudal abdominal mass involving bladder, urethra, colon, rectum, sublumbar lymph nodes.
  • Causes of fecal tenesmus: colon/rectum/anus disease.
  • Causes of preputial discharge.
  • Causes of reluctance to move: orthopedic/neuromuscular disease

Treatment

Initial Symptomatic Treatment

  • See individual diagnosis for details of treatment.
  • BPH- neuter, anti-androgen therapy (Finasteride).
  • Prostatitis- appropriate systemic antibiotics +/- aspiration abscess.
  • Neoplasia- surgical resection.
  • Radiation.

Monitoring

  • Risk of sepsis and bacteremia high in acute bacterial prostatitis or prostatic abscess → close monitoring for first 48 h antibiotics.

Subsequent Management

Treatment

  • In some chronic prostatitis cases, long-term antibiotics are needed to keep infection under control.

Monitoring

  • Rectal examination to determine size of prostate.
  • Subsequent prostatic (via prostatic washes or ejaculate) and urine or semen samples, taken one week and one month after finishing antibiotics, need to have a negative culture. Treat as a complicated UTI.
  • Monitor development of metastases in neoplastic disease.

Outcomes

Prognosis


Good
  • Benign prostatic hypertrophy.
  • Squamous metaplasia.
  • Prostatic calculi.
  • Prostatic cysts.
Guarded
  • Bacterial prostatitis.
  • Prostatic abscess.
Poor
  • Prostatic neoplasia.

Expected Response to Treatment

  • Reduction in size of prostate (2-3 weeks) in benign prostatic hypertrophy, prostatitis and cysts.
  • Negative prostatic fluid culture and urine culture one month after finishing antibiotics.

Reasons for Treatment Failure

  • Recurrence or development of obvious metastatic disease following surgery for prostatic neoplasia.
  • Development of prostatic abscess after prostatitis has not been well controlled by antibiotic therapy.
  • If several prostatic diseases present concurrently (for instance infection/neoplasia) and not recognized.
  • Tenesmus may continue due to a perineal hernia.
  • Prostatectomy may → urinary incontinence.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Bommer N (2006) Treatment of prostatic diseases. UK Vet 11 (4), 17-23 VetMedResource.
  • Bommer N (2006) A review of the pathophysiology of prostatic diseases. UK Vet 11 (3), 20-26 VetMedResource.

Other Sources of Information