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:
- Acute and chronic bacterial prostatitis Acute prostatitis.
- Prostatic or periprostatic cyst Prostate: cyst.
- Prostatic neoplasia Prostate: neoplasia.
- Prostatic squamous metaplasia.
- Prostatic calculi.
- 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.
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
.
- Localized peritonitis.
- Thoracic radiographs Radiography: thorax indicated to rule out pulmonary metastases.
- 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.
Urinalysis
- Bacturia; at least one positive urine culture on several samples.
- Hematuria Urinalysis: blood.
- Pyuria.
- Proteinuria Urinalysis: protein.
- 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).
- Leukocytosis, left shift in severe prostatic infections or leukopenia in some cases.
- Increased liver enzymes (endotoxemia).
- 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.
- Bacterial prostatitis.
- Prostatic abscess.
- 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.