Prostate diseases

From Dog
Advanced prostatic hyperplasia in a dog[1]
Prostatic adenocarcinoma in a neutered dog. Prostate is on the left and has a central cavity of necrosis. The bladder is central right.[2]
Fine needle aspirate from a dog with prostatic squamous metaplasia[3]
Chronic follicular cystitis and purulent prostatitis in a 13-year-old Labrador[4]

The canine prostate is a secondary-sex organ and neuroendocrine gland which produces ejaculate as part of sexual reproduction and responds to somatic sexual arousal via the central nervous stimulation.

The size and weight of the prostate vary depending on the age, breed, and body weight of the dog. The first histological signs of activity appear at about four months of age, and prostatic acinar cells become periodic acid-Schiff (PAS)-positive at twenty-four weeks of age, suggesting the beginning of secretory activity[5].

Because the canine prostate is bilobed with a prominent medium septum but is without zonal structures and has a fibromuscular capsule surrounding the corpus prostate (body)[6]. The prostate capsule acts similar to the blood-brain barrier, penetration of the prostatic capsule with antimicrobials, chemotherapy and other therapeutic medicines can be prolonged and difficult.

Additional to this is the fact that the prostate has limited expansile properties, and various diseases such as infections and neoplasms invariably is limited to chronic expansion which occurs over many weeks. Prostate-associated pain is usually low-grade due to intraprostatic pressure which is alleviated by gradual expansion of the fibromuscular capsule.

Cell proliferation and differentiation of the prostatic epithelium are controlled primarily by androgens, the most potent of which is testosterone[7]. Testosterone is converted to the most potent dihydrotestosterone by 5alpha-reductase within the prostate. Androgen interacts with androgen receptors to regulate normal growth of the prostate and has also been implicated in both the progression of benign prostate hyperplasia and prostate cancer in dogs[8].

The canine prostate also has receptors for leutinizing hormone and follicle stimulating hormone[9], and actively responds to these hormones at differing times related to seasonal changes and female estrus cycles. Androgens are critical in prostate development during puberty, as well as disease development, especially prostatic hyperplasia[10].

Normal dog urine usually contains traces of prostatic antigens, similar to human prostatic antigens used to assess prostatic carcinoma. One antigen in dog urine, prostatic lallikrein is identical to that found in dog dander, and is highly allergic[11], but its clinical relevance is currently unknown.

The activity of these neuroendocrine functions can be modulated with use of exogenous drugs such as deslorelin, a gonadotrophin releasing hormone agonist[12].

Bacterial infection, endocrine influence, immunological dysfunction and stress are reported to be factors in development of prostatic inflammation[13].

Diseases of the prostate include:

  • Congenital diseases
- Hypospadias - prostate absence[14]
- Persistent Müllerian duct syndrome[15] - Miniature Schnauzer predisposition
- Mycoplasma canis[19]
- Leishmania spp[20]
- Brucella canis[21]
- Bacteroides spp
- Blastomyces spp
- prostatic adenocarcinoma[22]
- Prostatic hyperplasia - usually older dogs
- Prostatic squamous metaplasia
- Prostatic adenocarcinoma
- Prostatic lymphoma
  • Miscellaneous causes
- Prostatic cysts[23]
- Rectourethral fistula[24]
- Emphysematous prostatitis[25][26]

Regardless of cause, prostatic diseases consistently cause similar clinical symptoms of tenesmus, dysuria, hematuria and cystitis.

Additional clinical signs such as fever, malaise, caudal abdominal pain, incontinence and anorexia are often indicative of bacterial infections or neoplasia.

Although prostatic diseases may occur in young dogs, older entire dogs are commonly affected with less serious conditions such as benign prostatic hyperplasia.

Interestingly, although benign prostatic hyperplasia is uncommon in neutered male dogs, the risk of developing prostate cancers, particularly prostate adenocarcinoma, transitional cell carcinoma and carcinoma is higher in this group[27].

Diagnosis of prostatic disease should be undertaken step-wise, commencing with routine hematology and biochemistry, rectal palpation of the prostate gland, ultrasonography, and radiographic, CT or MRI imaging studies.

Collection of urine and culturing for bacteria, fungi and detection of neoplastic cells is mandatory for a full diagnostic workup.

Definitive diagnosis usually requires fine-needle percutaneous, laparoscopy-guided or surgical biopsy of the prostate[28].

In non-metastatic prostatic diseases, prostatectomy should be considered a safe surgical procedure with good curative rates despite its technical challenges.

Other modalities such as transrectal microwave ablation[29] or histotripsy (ultrasound acoustic cavitation) should also be considered as viable high-tech options[30].

References

  1. University of Guelph
  2. University of Guelph
  3. Ireland Veterinary Journal
  4. University of Lisbon
  5. Kawakami, E et al (1991) Histological observations of the reproductive organs of the male dog from birth to sexual maturity. J Vet Med Sci 53:241–48
  6. Lee KJ et al (2011) Computed tomography of the prostate gland in apparently healthy entire dogs. J Small Anim Pract 52(3):146-151
  7. Dorso L et al (2008) Variability in weight and histological appearance of the prostate of beagle dogs used in toxicology studies. Toxicol Pathol 36(7):917-925
  8. Shidaifat F (2009) Age-dependent expression of 5alpha-reductase and androgen receptors mRNA by the canine prostate. Physiol Res 58(1):155-158
  9. Ponglowhapan S et al (2012) Expression of luteinizing hormone and follicle-stimulating hormone receptor in the dog prostate. Theriogenology 78(4):777-783
  10. Wilson JD (2011) The critical role of androgens in prostate development. Endocrinol Metab Clin North Am 40(3):577-590
  11. Mattsson L et al (92009) Prostatic kallikrein: a new major dog allergen. J Allergy Clin Immunol 123(2):362-368
  12. Palm J & Reichler IM (2012) The use of deslorelin acetate (Suprelorin®) in companion animal medicine. Schweiz Arch Tierheilkd 154(1):7-12
  13. Suwa, T et al (2001) A retrospective analysis of background lesions and tissue accountability for male accessory sex organs in Fischer-344 rats. Toxicol Pathol 29:467–478
  14. Jurka P et al (2009) Hypospadias in six dogs. Vet Rec 164(11):331-333
  15. Breshears MA & Peters JL (2011) Ambiguous genitalia in a fertile, unilaterally cryptorchid male miniature schnauzer dog. Vet Pathol 48(5):1038-1040
  16. Juodziukyniene N et al (2010) Effect of age, hyperplasia and atrophy on collagen parameters in dog prostates. Pol J Vet Sci 13(3):479-485
  17. Jiang Z et al (2010) Trans-rectal ultrasound-coupled spectral optical tomography of total hemoglobin concentration enhances assessment of the laterality and progression of a transmissible venereal tumor in canine prostate. Urology 77(1):237-242
  18. Agut A et al (2006) A urethrorectal fistula due to prostatic abscess associated with urolithiasis in a dog. Reprod Domest Anim 41(3):247-250
  19. L'Abee-Lund TM et al (2003) Mycoplasma canis and urogenital disease in dogs in Norway. Vet Rec 153(8):231-235
  20. Mir F et al (2012) Subclinical leishmaniasis associated with infertility and chronic prostatitis in a dog. J Small Anim Pract 53(7):419-422
  21. Corrente M et al (2010) Detection of Brucella canis in a dog in Italy. New Microbiol 33(4):337-341
  22. Teske E et al (2002) Canine prostate carcinoma: epidemiological evidence of an increased risk in castrated dogs. Mol Cell Endocrinol 197(1-2):251-255
  23. Ragetly GR et al (2009) What is your diagnosis? Discrete prostatic cysts. J Am Vet Med Assoc 234(9):1127-1128
  24. Silverstone AM & Adams WM (2001) Radiographic diagnosis of a rectourethral fistula in a dog. J Am Anim Hosp Assoc 37(6):573-576
  25. Elsinghorst TA (2003) First cases of animal diseases published since 2000. 1. Dogs. Vet Q 25(3):112-123
  26. Rohleder JJ & Jones JC (2002) Emphysematous prostatitis and carcinoma in a dog. J Am Anim Hosp Assoc 38(5):478-481
  27. Bryan JN et al (2007) A population study of neutering status as a risk factor for canine prostate cancer. Prostate 67(11):1174-1181
  28. Holak P et al (2010) Laparoscopy-guided prostate biopsy in dogs - a study of 13 cases. Pol J Vet Sci 13(4):765-766
  29. Li ZC et al (2011) Ultrasound-guided transrectal microwave ablation of the prostate in dogs. Zhonghua Nan Ke Xue 17(9):813-816
  30. Schade GR et al (2012) Endoscopic assessment and prediction of prostate urethral disintegration after histotripsy treatment in a canine model. J Endourol 26(2):183-189