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Do Dogs Get Prostate Problems?

Definition

 

The diseases of the prostate gland are most common in the intact male dog reproductive tract and less common in other domestic animals. The diseases of the prostate include:-


  1. Benign prostatic hyperplasia (BPH) is the most common prostatic disease

An illustration comparing healthy and hypertrophic prostate glands
An illustration comparing healthy and hypertrophic prostate glands

2. Cystic benign prostatic hyperplasia (CBPH) - prostatic and paraprostatic cysts

An illustration comparing healthy and cystic hypertrophic prostate glands
An illustration comparing healthy and Cystic hypertrophic prostate glands

3. Infectious prostatitis (IP) - Acute or chronic


4. Prostatic abscesses (PA)


5. Prostatic neoplasia (PN) - Prostatic Adenocarcinoma - More common in castrated dogs and typically affects dogs over 10 years of age

An illustration comparing a healthy and cancerous prostate gland
An illustration comparing a healthy and cancerous prostate gland

6. Prostatic calculi (PC) are rare and are usually classified as primary (endogenous) stones or secondary (extrinsic) stones. Endogenous stones are commonly caused by obstruction of the prostatic ducts around the enlarged prostate by benign prostatic hyperplasia (BPH) or by chronic inflammation

An illustration of prostatic calculi compared to normal prostate.
An illustration of prostatic calculi compared to normal prostate.

Multiple diagnostic modalities and several evaluations are required to differentiate prostatic conditions and to determine whether they are benign or malignant as they are clinically challenging.

What are the causes of the various prostatic diseases?

 

The factors that predispose dogs to prostatic diseases include:-

  1. Uncastrated males

  2. Advanced age

  3. Urinary tract infection (prostatic infection).

Senior uncastrated dogs (dogs older than 5 years) have altered androgen/estrogen (male/female) hormone ratio that leads to benign prostatic hyperplasia (BPH), prostatic cysts or bacterial prostatitis. Urinary tract infection leads to a prostatic infection by an opportunistic organism, e.g. Escherichia coli, Staphylococcus, Streptococcus, Mycoplasma spp., occasionally, Proteus and Pseudomonas spp or anaerobic organisms. Prostatic squamous metaplasia is an epithelial cell degeneration caused by excess amounts of oestrogen secretion, e.g., due to a Sertoli cell tumour or iatrogenic.

An illustration of the stages of prostatic cancer
An illustration of the stages of prostatic cancer

What are the clinical signs of a prostatic disease?

 

Prostatic diseases cause either the enlargement or cancerous changes of the prostate gland. This leads to pressure being exerted on the ventral rectum and/or the urethra leading to the following clinical signs:-

  1. Lower urinary tract symptoms

    1. Intermittent preputial bloody discharge without urination

    2. Haematuria may occur mostly towards the end of urination. Blood dripping from the urethra is sometimes noted.

    3. Unlike in humans, dysuria is uncommon in dogs. In men, dysuria is caused by an increase in pressure on the urethra due to concentric hypertrophy of the prostate. In dogs, prostatic hyperplasia is diffuse and the enlarged prostate will change position by moving into the abdominal cavity.

    4. Urinary retention (anuria) in dogs is reported when large cavities and neoplasia are present in the prostate.

An illustration of the urinary system
An illustration of the urinary system

2. Changes in the conformation of semen

  1. Haematospermia without changes in semen quality is the most common sign in the early stages of benign prostatic hyperplasia and prostatitis.

  2. In the later stages, a decrease in motility and morphology and an increase in tail abnormalities are particularly common.


3. Gastrointestinal symptoms

  1. The enlarged prostate may compress the colon leading to constipation (flattened stools),

  2. Tenesmus or intermittent diarrhoea.

  3. Severe constipation may promote perineal hernia.


4. Locomotor disorders

  1. Musculoskeletal disorders such as stiffness, lameness, paresis or oedema of the hindlimbs have been reported.

  2. In rare cases, infections of the prostate may induce bacterial emboli leading to lumbosacral spondylodiscitis.

3D illustration of a dogs anatomy
3D illustration of a dogs anatomy

5. Systemic signs

a. Hyperthermia (fever)

b. General unexplained deterioration of body condition may be the only clinical manifestation of prostate diseases such as abscess, prostatitis and tumour.


6. Digital rectal palpation The prostate gland is palpable per rectum unless prostatomegaly is severe enough to cause repositioning cranially into the abdomen cavity. The normal prostate is symmetrical and smooth, with a distinct dorsal median groove. Digital palpation of the normal prostate in the dog should not be painful. Asymmetry of the prostate and loss of the dorsal median groove may be observed in cases of severe parenchyma alterations: prostatic cavity, prostatitis and neoplasia.

Digital rectal examination (Illustration)
Digital rectal examination (Illustration)

Penile discharge in dogs
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How are prostatic diseases diagnosed?

 

Definitive diagnosis of any prostatic disorder requires histopathologic evaluation of prostatic tissue, but less invasive diagnostics, e.g. physical examination findings, and abdominal radiographs may help define the size, shape, and position of the prostate gland. The sublumbar lymph nodes, lumbar vertebrae, and bony pelvis should be evaluated radiographically for evidence of periosteal new bone and bony metastases.

An x-ray showing the spine around the lumbar region
An x-ray showing the spine around the lumbar region

Transabdominal ultrasonography is the best imaging modality for the evaluation of the prostate because it allows for the evaluation of the prostatic parenchyma and adjacent soft-tissue structures. Laboratory studies of urine, semen, prostatic fluid or prostatic tissue are also useful.

Ultrasound images of the prostate gland
Ultrasound images of the prostate gland

Cystoscopy is an endoscopy of the urinary bladder via the urethra carried out with a cystoscope. The urethra is the tube that carries urine from the bladder to the outside of the body. The cystoscope has lenses like a telescope or microscope. Endoscopic examination of the bladder (cystoscopy) and urethra (urethroscopy) are performed in dogs with various urinary tract problems, such as tumours or difficulty urinating. Biopsies are collected during this procedure so that a definitive diagnosis can be made.

A 3D illustration of urinary bladder during cystoscopy
A 3D illustration of urinary bladder during cystoscopy

How are the various prostatic diseases treated?

 
An illustration showing the various treatment methods for prostatitis
An illustration showing the various treatment methods for prostatitis

  1. Prostatic Hyperplasia: Castration is curative in both BPH and CBPH patients.

  2. Antiandrogen Therapy: In breeding dogs, medical antiandrogen therapy is an option if defecation is difficult. The canine antiandrogen dose can be extrapolated from the human dose of finasteride; 1.25–5 mg/dog PO q24h; higher doses (0.10–0.20 mg/kg PO q24h) have been evaluated without problems. Libido and semen quality are not compromised, but the prostatic fluid component of the ejaculate is markedly diminished. NB: Finasteride is not licensed for use in dogs but is commonly used in speciality reproductive practice.

  3. Other Medical Therapies

    1. Alternative medical therapies (eg, estrogenic or progestational compounds) are not advised because of their negative effects on circulating testosterone concentration and spermatogenesis and induction of prostatic metaplasia (estrogen), the potential for myelosuppression (estrogen), insulin and glucose dysregulation (progesterone), and mammary neoplasia (estrogen).

    2. Infectious Prostatitis: Treatment must be prompt and aggressive.

    3. Fluid therapy is necessary to correct dehydration and shock.

    4. Large prostatic abscesses are treated most effectively by surgical drainage and omentalization. Abscesses may also be drained by fine-needle aspiration under ultrasound guidance.

    5. Acute Infectious Prostatitis: Pending the results of culture and susceptibility testing, treatment with a fluoroquinolone and potentiated amoxicillin should be initiated. Antibiotic treatment for acute prostatitis should be continued for ≥4 weeks. Urine or prostatic fluid should be recultured 1 week after antibiotic therapy is discontinued and again 2–4 weeks later to confirm the infection has resolved.

    6. Chronic Infectious Prostatitis (IP): Chronic IP may be difficult to clear because the blood–prostate barrier is quite effective in preventing many drugs from penetrating into the prostatic parenchyma. In patients with chronic IP, only highly lipophilic agents (eg, erythromycin, clindamycin, trimethoprim–sulfonamide, chloramphenicol, carbenicillin, enrofloxacin, ciprofloxacin) can cross into the prostate. Antibiotic therapy should be based on culture and susceptibility results from urine and prostatic tissue. Treatment should be continued for ≥4 weeks. To identify resistance to antibiotics or persistent infection, cultures should be repeated during and for several months after antibiotic therapy is discontinued. Castration improves the response to treatment of chronic bacterial prostatitis. Surgical castration may be postponed until urine or prostatic culture is negative while the patient is receiving antibiotic therapy to avoid creating sequestration of infectious material in an involuting gland.

    7. Prostatic Neoplasia (PN): PN is not responsive to antiandrogen therapy. Prostatectomy is complicated by urinary incontinence and is rarely curative because of local metastatic disease. Chemotherapy of various prostatic tumours can be palliative. Palliative radiotherapy can provide short-term relief of obstructive disease.

What are the prognoses of the various prostatic diseases?

 

Generally, prognoses are as follows:-

  1. BPH: good for fertility, benign

  2. CBPH: good for fertility, benign unless secondary infection occurs

  3. IP: guarded to fair for fertility if managed aggressively

  4. Prostatic neoplasia: poor fertility, a malignant disease


References

 

Johnston SD, Root Kustritz MV, Olson PNS, 2001a: Canine and Feline Theriogenology. WB Saunders Company, Philadelphia, p. 355.


Kustritz MVR, Klausner JS, 2000: Prostatic diseases. In: Ettinger SJ (ed), Textbook of Veterinary Internal Medicine5th edn. WB Saunders, Philadelphia, pp. 1687–1698.


Davidson, A. P. (2014). Prostatic disease. Clinician’s Brief, 1, 81-85.


Maurey-Guenec C, 2007: Approche clinique des affections prostatiques. Pratique vét Comp Anim38, 7–8.


Kustritz, M. V. R., Johnston, S. D., Olson, P. N., & Lindeman, C. J. (2005). Relationship between inflammatory cytology of canine seminal fluid and significant aerobic bacterial, anaerobic bacterial or mycoplasma cultures of canine seminal fluid: 95 cases (1987–2000). Theriogenology, 64(6), 1333-1339.


Davidson, A. P., & Baker, T. W. (2009). Reproductive ultrasound of the dog and tom. Topics in companion animal medicine, 24(2), 64-70.


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