26 Disorders of the Prostate
No medical therapy has been demonstrated to be as effective for decreasing clinical signs of BPH and prostate size as castration. I usually recommend medical therapy be used until you have the breedings you want from that male or have collected and frozen semen. Castration should be performed at some point.
That is a good question. In some dogs there probably is a certain degree of infection or inflammation throughout the reproductive tract, including the prostate and testes. In other dogs it is thought that the abnormal prostatic fluid, which is all the fluid portion of the ejaculate, alters the morphology and motility of spermatozoa as they are ejaculated and intermingle.
The prostate encircles the neck of the urinary bladder such that the urethra runs directly through the center. There are two prostatic lobes, separated by fibrous tissue. Growth and function of the prostate are androgen dependent. Under the influence of testosterone and its metabolite, dihydrotestosterone (DHT), prostatic cells increase in number (hyperplasia) and size (hypertrophy). As long as a male dog is intact, progressive increase in prostate size will occur. Castration causes profound prostate atrophy.
Benign prostatic hypertrophy/hyperplasia (BPH) is an androgen-dependent increase in cell number and size. This is an age-related phenomenon; by 5 years of age, all intact male dogs have some degree of BPH, the most common prostatic disorder diagnosed in dogs.
Dogs may have evidence of BPH that can be identified on radiographs or on physical examination and exhibit no clinical signs of disease. If there is clinical evidence of BPH, the most common manifestation is dripping of bloody fluid from the tip of the penis unassociated with urination. This clinical sign may be evident only when the male is exposed to an estrous female, causing prostatic contractions. The enlarged prostate gland has an excellent blood supply, and the bloody prostatic fluid runs into the bladder as well, giving the appearance of bloody urine (hematuria). As the enlarged prostate presses up against the colon, straining to defecate or passage of ribbon-like feces may be seen. The dog feels well otherwise.
Diagnosis may be made based solely on rectal palpation of the prostate and submission of semen for cytology and culture. Semen color may be abnormal (Figure 26-3). Imaging and aspiration of the prostate may be performed (Figure 26-4 and Table 26-1).
(Courtesy Dr. Kaitkanoke Sirinarumitr.)
|Diagnostic Test||Result and Interpretation|
|Rectal palpation||Symmetrical, nonpainful. The prostate may be so enlarged as to pull the urinary bladder into the abdomen. The enlarged prostate may be palpable per abdomen.|
|Semen collection||Color of prostatic fluid varies from clear to tan to maroon (Figure 26-3).|
|Prostatic radiographs or ultrasound||Contrast radiographs demonstrate forward movement of the bladder and flattening of the back of the usual teardrop-shaped urinary bladder by presence of the enlarged prostate. On ultrasound, the prostatic tissue is uniform (Figure 26-4).|
|Aspirate or biopsy||Normal cells are present. There are no inflammatory changes.|
In dogs with no clinical signs of disease, no treatment may be necessary. If treatment is required, castration is the best therapy, causing the quickest and most complete prostate atrophy. If castration is undesirable, medical therapy with the human drug finasteride (Proscar or Propecia) may be used to decrease prostate size. Finasteride is administered daily for 1 to 4 months. A significant decrease in prostate size and coincident clinical signs occurs within 4 to 6 weeks of therapy in most dogs. After withdrawal of the drug, the prostate gradually will increase in size again. Treatment of dogs with finasteride is not associated with decline in semen quality. Breeding of dogs on finasteride has not been associated with small litter size or induction of birth defects in pups. Other therapies described for use in humans, such as the use of the herb saw palmetto, have not been demonstrated to be useful therapies for BPH in dogs. Other hormone therapies, including use of progesterone or estrogen, have been described for use in dogs but may have undesirable side effects.
Dogs with BPH generally have normal semen quality. The presence of blood in the ejaculate (hemospermia) does not appear to alter fertility for natural service or artificial insemination with fresh semen. Semen containing blood is unsuitable for use as chilled or frozen semen; even after centrifugation of the sample to remove the spermatozoa from the bloody fluid, the spermatozoa do not tolerate the chilling or freezing process well. The presence of BPH predisposes the dog to prostate infection, which can alter semen quality.