Challenging cases in internal medicine: A dog with an enlarged prostate and bloody preputial discharge - Veterinary Medicine
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Challenging cases in internal medicine: A dog with an enlarged prostate and bloody preputial discharge
These clinicians puzzled over this neutered dog's clinical signs and diagnostic test results, which seemed to indicate a disease only found in intact males.


Initial treatment and further evaluation

Figure 2: An ultrasonogram obtained on admission. Note the mostly uniform echotexture of the prostatic parenchyma. The white arrow indicates a small cyst in the dorsal prostate.
Since all physical and laboratory data pointed to a diagnosis of benign prostatic hyperplasia, we decided to further evaluate the possibility of this disease before proceeding with more invasive diagnostic testing. With that in mind, a sample for a baseline testosterone concentration was submitted. While awaiting these results, we instituted antimicrobial therapy with enrofloxacin (5 mg/kg orally b.i.d.) empirically to treat a possible undetected prostatitis. We chose enrofloxacin for its excellent distribution into the prostate gland. We discontinued the antibiotic therapy after one week since the blood-tinged preputial discharge continued despite therapy.

One week after our initial evaluation, the baseline testosterone concentration returned as 2,747 pg/ml (reference range for castrated dogs < 50 pg/ml; reference range for cryptorchid dogs 100 to 500 pg/ml; reference range for intact dogs > 1,000 pg/ml). Satisfied that this dog was producing a testosterone concentration adequate to predispose the dog to benign prostatic hyperplasia, we decided to perform a laparoscopic evaluation of the abdomen to attempt to identify an intra-abdominal testicle and obtain a prostatic biopsy sample. Preoperatively, an electrocardiogram showed intermittent atrial premature contractions; however, echocardiography revealed no evidence of heart chamber enlargement or valvular insufficiency.

At laparoscopy, both vasa deferentia were seen, as was the left inguinal ring. A vascular bundle that traversed the left inguinal ring appeared to be thrombosed, but there appeared to be no vas deferens exiting this side. No structures were seen traversing the right inguinal ring. The left vas deferens was followed for about 4 cm from its approximated urethral insertion, where the vas deferens ended abruptly. The right vas deferens was followed about 5 cm from its approximated urethral insertion, at which point a small mass of tissue was identified. This mass was externalized through a trocar site located about 2 cm paramedially to the midprepuce on the right side. It was removed along with about 3 cm of the right vas deferens and submitted for histopathologic examination. The regions of the prostate seen laparoscopically revealed no gross abnormalities; however, only the right lobe of the prostate was isolated (through blunt dissection). Several samples of the prostate were obtained with a Tru-Cut biopsy needle and submitted for histopathologic examination as well.

Anesthetic recovery was normal, and the dog was discharged the next day pending histopathologic examination of both the prostatic biopsy samples and the mass removed from the distal end of the right vas deferens. Carprofen (2.2 mg/kg orally b.i.d. for three days) was dispensed for postoperative pain relief.

Histopathologic examination of the prostatic biopsy samples revealed mild plasmacytic prostatitis with well-differentiated prostatic glands; no evidence of cysts, infection, or neoplasia was noted. The microscopic appearance of the biopsy samples was consistent with benign prostatic hyperplasia. Examination of the right-sided mass at the tip of the vas deferens revealed focal lymphocytic-plasmacytic cellulitis with mineralization and connective tissue. No testicular tissue was seen in this mass.

Table 4: Endocrinologic Testing Results
Given our biopsy confirmation of benign prostatic hyperplasia and prostatitis and lack of evidence of a retained intra-abdominal testicle, we decided to perform provocative testing to further evaluate the presence of retained testicular tissue. We performed a human chorionic gonadotropin (HCG)-response test (Table 4) to support our concern that this dog had viable testicular tissue that was producing the testosterone needed to cause benign prostatic hyperplasia. The response to HCG seen in this patient thus prompted us to resume our search for an undescended intra-abdominal testicle that had evaded laparoscopic exploration or, less likely, an extratesticular source of testosterone.


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