1. Benign prostatic hypertrophy/hyperplasia (BPH)
In most cases, BPH does not cause any clinical signs. Only if the prostate is so enlarged that it compresses the colon and interferes with defaecation are dogs usually presented to the veterinarian.
Other clinical signs frequently include hemorrhagic discharge from the urethra. On rectal examination, the prostate is found to be enlarged, symmetrical and painless. Ultrasound examination usually reveals an enlarged prostate with loss of the normal homogeneous appearance.
Treatment is required in patients with clinical signs of prostatic disease. The treatment of choice is surgical castration. A 50% reduction of the size of the prostate can be expected within three weeks. Alternatively, chemical castration is possible.1
A variety of pharmaceutical agents have been tested in dogs, including delmadinone acetate (Tardak, 1-2 mg/kg SQ, repeated after 8 days if no response), medroxyprogesterone acetate (Depo-promone, 3 mg/kg SQ twice at 4 week interval) and megestrol acetate (Minipil, 0.55 mg/kg PO for 4 weeks).
The synthetic steroid finasteride (5á-reductase inhibitor), which is used effectively for the treatment of BPH in humans, has also successfully been used to induce prostate atrophy in dogs without decreasing sperm quality or libido (Proscar, 5mg per dog between 10 and 50 kg every 24 hours).
More recently Ozasterone acetate (Ypozane ) has been licensed for the treatment of BPH in dogs. It blocks the uptake of testosterone by prostate cells and blocks the androgen receptor in the cell, thereby inhibiting the binding of dihydro-testosterone to the receptor. It therefore has a rapid onset of action. It is given at a dose of 0.25-0.5mg/kg SID for 7 days and has an effect for about six months.
2. Prostatitis
Clinical signs associated with bacterial prostatitis include depression, painful rectal palpation, fever, straining to urinate or defaecate and a stiff-legged gait. Occasionally in breeding male dogs the only sign of prostatic bacterial infection may be poor semen quality leading to sterility. Definitive diagnosis is made by cytological examination and quantitative isolation of bacteria from prostatic fluid obtained by ejaculation or prostatic massage. Normal prostatic fluid should contain less than 10,000 bacteria per ml.1
Treatment of bacterial prostatitis involves antimicrobial therapy and castration or anti-androgen therapy. Antibiotic therapy should be based on sensitivity of the isolated bacteria and on the ability of the antibiotic to reach therapeutic concentrations on prostatic parenchyma.
Permeability of the blood-prostate barrier for a given antimicrobial agent depends on its lipid solubility and ability to diffuse along a pH gradient. Trimethoprim-sulfa, chloramphenicol and enrofloxacin are known to reach prostatic parenchyma in therapeutic concentrations and are effective in treating most bacterial infections of the prostate.1
3. Prostatic abscess
Clinical signs of prostatic abscess are similar to prostatitis. Definitive diagnosis is made on ultrasound examination, which allows the typical fluid-filled cavities of the abscessed prostate to be recognised. In severe cases, dogs with prostatic abscess, peritonitis and septicemia may show signs of septic shock.2
Prostatic abscesses should be considered relative emergencies and should be treated surgically in addition to antimicrobial therapy described for bacterial prostatitis. The prostate is approached through a caudal midline coeliotomy and periprostatic fat is carefully dissected from the prostate. The prostatic vascular supply, hypogastric and pelvic nerves are found on the dorsal aspect of the prostate and should be preserved.
It is now recognised that properties of the omentum including secretion of an angiogenic factor and immune and phagocytic functions can be used in the surgical treatment of prostatic diseases such as abscesses. Intracapsular omentalisation is the treatment of choice for prostatic abscessation.
Bilateral stab incisions are made in the lateral aspects of the prostate (see Figure 1). Pus is removed from the abscess cavities by suction to minimise abdominal contamination. All abscess cavities are broken down by digital exploration. Omentum is then packed in the cavities, passed around the urethra and fixed to the capsule of the prostatic abscess.2 Castration should be performed at the same time as surgical treatment of the prostatic abscess.
Preparation for prostatic surgery
Anaesthesia
As the prostate is located in the caudal abdomen, dogs undergoing prostatic surgery are good candidates for perioperative analgesia using epidural anaesthesia. Opioids are preferred over local anaesthetics because of the lower risk of causing urinary retention post-operatively.
Urinary catheter
Cysts and abscesses can greatly alter the gross appearance of the prostate and the surgeon may find it difficult to identify normal anatomical structures. In order to identify the location of
the urethra, placement of a urinary catheter before or during surgery is highly recommended. In addition, the catheter can be attached to a closed urine collection bag, allowing the bladder to remain empty for the duration of the procedure.
4. Prostatic and para-prostatic cysts
Clinical signs include tenesmus or dysuria. Ultrasonography is the imaging technique of choice for recognising anechoic cystic lesions.1-3
Retention cysts and para-prostatic cysts should be drained surgically. Very large cysts may be partially resected. Omentum is fixed to the remaining cyst to avoid recurrence.2 Castration is also recommended in dogs with cystic prostatic disease.
5. Prostatic squamous metaplasia
Clinical signs are related to the enlargement of the prostate and are similar to the ones described for BPH and the condition may also be associated with cystic changes. In addition, the dogs may show signs of feminisation related to hyperoestrogenism (attraction for other males, development of mammary
glands).
Diagnosis is made by cytological examination of cells obtained by fine needle aspiration biopsy or by collection of prostatic fluid.
Treatment of squamous metaplasia of the prostate involves castration and removal of the tumour-producing oestrogens (see Figure 2). Additional surgical treatment of prostatic cysts may also be necessary in some cases.
6. Prostatic neoplasia
Canine PCA has a higher incidence in castrated individuals than in intact males and it differs from human PCA in that it cannot be treated by androgen ablation therapy. In this respect, canine PCA resembles the late stage of PCA in humans, also called androgen-independent PCA.
PCA should always be considered with a high degree of suspicion in castrated dogs showing signs of prostatic disease. The diagnosis is usually made by cytological examination of a fine needle aspirate of the prostate performed under ultrasound guidance.
Due to the high metastatic rate of prostate carcinoma, both local and systemic treatment are necessary to control the disease. Radical prostatectomy in dogs with prostatic disease is associated with a high incidence of peri-operative mortality and post-operative incontinence and is therefore not an acceptable treatment option for dogs with prostatic carcinoma.
Various techniques for partial or subtotal prostatectomy have been described. Partial prostatectomy can be useful as a symptomatic treatment of the disease by decreasing the size of the prostate and reducing faecal straining.4
Photodynamic therapy (PDT) has also been used for the local control of prostate carcinoma in dogs. PDT combines the administration of a photosensitiser and the subsequent illumination of the target organ with light of a determined wave length. The light is absorbed by the photosensitiser causing photochemical mechanisms leading to tissue necrosis.5,6
No effective chemotherapeutic protocol is available for the systemic treatment of PCA in dogs. COX-2 is expressed in various types of canine cancer including PCA, and is thought to play a role in carcinogenesis. This is supported by evidence that treatment with COX-2 inhibitors may be beneficial in the management of certain tumours in dogs.
Although it has been shown that COX-2 is expressed in canine PCA7, the effect of NSAIDs on the clinical outcome of dogs with PCA has not been extensively investigated. Despite this, treatment with a selective COX-2 inhibitor such as meloxicam or firocoxib is generally recommended.
For dogs with severe stranguria or urethral obstruction caused by neoplasms of the prostate, palliative treatment with intraluminal stents can be effective in improving quality of life for several months.8
- Johnston, S.D., Kamolpatana, K., RootKustritz, M. V. and Johnston, G. R. (2000) Anim Reprod Sci 60-61: 405-415.
- White, R. A. S. (2000) Clin Tech in Small An Pract 15 (1): 46-51.
- Dorfmann, M., Barsanti, J. (1995) Comp Cont Educ 17 (6): 791-810.
- L’Eplattenier, H. F., van Nimwegen, S. A., van Sluijs, F. J. and Kirpensteijn, J. (2006) Vet Surg 35: 406-411.
- Lucroy, M. D., Bowles, M. H., Higbee, R. G., Blaik, M. A., Ritchey, J. W. and Ridgway, T. D. (2003) J Vet Intern Med 17: 235-237.
- L’Eplattenier, H. F., Klem, B., Teske, E., van Sluijs, F. J., van Nimwegen, S. A. and Kirpensteijn, J. (2008) Vet J 178: 202-207.
- L’Eplattenier, H. F., Lai, C. L., van den Ham, R., Mol, J., van Sluijs, F. and Teske, E. (2007) J Vet Intern Med 21: 776-782.
- Weisse, C., Berent, A., Todd, K., Clifford, C. and Solomon, J. (2006) J Am Vet Med Assoc 229: 226-234.
