Introduction

Benign prostatic hyperplasia (BPH) is a common disease of intact male dogs. It is expected that nearly all intact males will have prostate enlargement associated with advanced age. While neuter will resolve the condition completely by way of removing androgens associated with prostatic tissue activity, many circumstances exist in which surgery is not the best option for the patient. Medical treatment in uncomplicated cases of benign prostatic hyperplasia is often successful and should be a consideration depending on the clinical health of the dog, surgical risk for the individual, and the function or occupation of the animal.

Indications for Medical Treatment

Given the recent interest in the impact of gonadectomy on both male and female dogs relating to a variety of non-neoplastic and neoplastic conditions, many veterinarians have shifted their original views of gonadectomy as being an “easy” choice relating to general health and well-being of the animal involved.¹ While a large amount of study remains to be pursued, several papers have suggested a possible link to increased incidence of orthopedic, cancerous, behavioral, and autoimmune conditions.^2,3 Depending on the breed, age, and other predispositions, it is important to consider whether the presence of testosterone may have a favorable presence for some conditions for that individual. Additionally, many owners with high performance animals, such as working dogs, express concern for an observed decrease in their animal’s ability to perform its job. Breeding dogs and show dogs are often preferred intact for current or future exhibitions and breeding plans. Owners may also have cultural or religious concerns regarding surgical alteration of their animals.

Aside from the predispositionary viewpoint, a clinician may also find themselves opting for medical therapy because of other risk factors for this dog. If the dog has a known significant surgical risk, such as a heart condition, it may be preferred to suppress the hormonal status rather than elect for a surgical option. Additionally, medical therapy may provide an option for temporary management if surgery is preferred but cannot be pursued due to the animal’s current condition, but is desired in the future.

If the animal is an optimal surgical patient, and the owner would like to pursue castration to resolve the condition, this is the best option for permanent resolution with no need for regular medication or follow-up. In some cases, castration may be required for resolution, despite medical attempts.

Diagnosis

Classic BPH signalment is in middle-age to older intact male dogs. It has been demonstrated that 50% of dogs have histologic evidence of BPH by 5 years of age.⁴ Neutered dogs are generally not affected by BPH or subsequent prostatitis. While some breeds appear anecdotally more commonly affected, such as the German Shepherd dog, all dogs are at risk for developing clinical BPH.

History alone may give a clinician a high suspicion of BPH as a possible diagnosis. Hematuria is commonly noted incidentally by the owner and brought as the primary concern. The owner may describe stranguria, or noting pulsatile, long urination as compared to previous urinary patterns. In extreme cases, the prostate may be large enough to cause flattened stools or difficulty defecating.

On physical examination, prostatic enlargement can sometimes be palpated transabdominally, especially in larger males with significant prostatic enlargement. Digital rectal exam should reveal a bilobed prostate, which is generally symmetric, smooth, and non-painful. In larger dogs, the prostate may be easiest to palpate when the non-dominant hand is used to pull the prostate toward the rectal examination hand transabdominally.

The most useful sample to assess prostatic health is prostatic fluid during semen collection or prostatic wash. The third fraction during canine ejaculation is normally clear, but is often red, pink, or orange in color in dogs with prostatic concerns. Visual observation can be supportive evidence, but centrifugation of this sample to collect cellular components into a pellet is excellent practice, in order to concurrently evaluate for possible prostatitis as part of the disease process. Culture of the prostatic fluid may also better define involvement of prostatitis as part of the prostatic enlargement.

Imaging can be performed to support diagnosis of BPH in a patient. Radiographs and ultrasound can both be useful tools, though ultrasound is preferred for measuring the prostate, evaluating for cystic changes, and evaluating echotexture. Ultrasound measurements can be performed by longitudinal or transverse approach transabdominally, but it is advised to perform multiple approaches to optimize accuracy of measurements.⁵

Treatment

Dogs with BPH need only be treated if symptomatic, or if cystic disease is present on ultrasound. Presence of prostatic enlargement is considered a normal finding in older intact males. Severe BPH may be responsive to medical therapy, but the best candidates for long-term medical treatment are those with milder ultrasonographic findings.

Medical therapy includes regular oral administration of 5-α reductase inhibitors. This family of drugs will prohibit conversion of testosterone to dihydrotestosterone (DHT).⁶ DHT is the primary modulator of growth and secretory prostatic function, so by reducing conversion, the hyperplastic nature of the prostate is decreased at a cellular level in both men and dogs with BPH.⁶ In the United States, the most inexpensive and commonly available 5-α reductase inhibitor is finasteride.

Initially, finasteride dosing for medium and large dogs is advised at 5 mg every 24 hours, while smaller dogs may receive 2 mg daily with positive clinical response. While undergoing initial treatment, once daily oral dosing is advised for the first three months. Ultrasonographic assessment should be repeated at this time, and dosing frequency reduced to every other day or twice weekly if prostatic health is improved and size is reduced. Rechecking patients every 3 months should be performed until stable clinical picture is observed on a given regimen; at this time, frequency of assessment can be reduced to every 6 months. 5-α reductase inhibitors have no significant side effects reported in dogs and can be tolerated safely long-term, and are recommended as long as the dog remains intact. Removal of medications will result in return of clinical prostate disease.

Surgical management of BPH may be required in refractory cases, or non-responsive cases. The best and most effective option for resolution of BPH is castration.⁶ Reduction in prostatic size after the removal of hormones is expected within 2–3 months.

Impact on Fertility

The prostate contributes a large component of the fluid relating to the normal canine ejaculate. As a result of reducing prostatic activity and secretory function, the ejaculate will often become more concentrated, and prostatic fraction may be reduced or absent. Varied opinions exist as to whether drugs should be reduced or spared temporarily to increase ejaculatory volume for natural breeding, however, samples for artificial insemination and collection for cryopreservation should not be negatively impacted. No impact on daily sperm production or fertility have been documented in dogs.⁶

Conclusions

Benign prostatic hyperplasia is a common diagnosis in dogs worldwide. The disease may be non-clinical and found incidentally on examination or through diagnostic testing, or it may present clinically and require treatment. While surgical treatment should be a first-line option for treatment for most patients, medical management can be an excellent alternative to resolve the clinical signs or disease risk for developing subsequent prostatitis.

References

1.  Root MV. Determining the optimal age for gonadectomy of dogs and cats. J Am Vet Med Assoc. 2007;231(11):1665–1675.

2.  Hart BL, Hart LA, Thigpen AP, Willits NH. Neutering of German Shepherd dogs: associated joint disorders, cancers and urinary incontinence. Vet Med Sci. 2016;2(3):191–199.

3.  Zink MC, Farhoody P, Elser SE, Ruffini, LD, Gibbons, TA, Rieger, RH. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas. J Am Vet Med Assoc. 2014;244(3):309–319.

4.  Berry SJ, Strandberg JD, Saunders WJ, et al. Development of canine benign prostatic hyperplasia with age. Prostate. 1986;9:363–373.

5.  Atalan G, Holt PE, Barr FJ. Ultrasonographic estimation of prostate size in normal dogs and relationship to bodyweight and age. J Small Anim Pract. 1999;40:119–122.

6.  Johnston SD, Root MV, Olson PNS. Canine and Feline Theriogenology. Philadelphia, PA: W.B. Saunders Company; 2001.