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.
May 01, 2004

A 5-YEAR-OLD, 114-lb (51.8-kg) neutered male German shepherd was examined because of a three- to four-week history of bloody preputial discharge and prostatomegaly. Initial evaluation by this dog's veterinarian had revealed marked prostatic enlargement on rectal palpation. Cytologic examination of a prostatic wash sample had revealed degenerative neutrophils but no bacteria or neoplastic cells. A two-week course of oral trimethoprim-sulfadiazine had been dispensed. The discharge resolved initially but returned when the antimicrobial therapy was discontinued. The dog was then referred to the University of Georgia College of Veterinary Medicine for further evaluation.

Initial diagnostic procedures

Table 1: Complete Blood Count Results
A review of this dog's history revealed that it was born unilaterally cryptorchid and had been castrated at 6 months of age. The testicle removed through an abdominal approach was not submitted for histopathologic examination. The location of the scrotal testicle (right or left side) was not noted.

Table 2: Serum Chemistry Profile Results
The dog was bright, alert, and responsive. Thoracic auscultation revealed an intermittent arrhythmia (consistent with a past diagnosis of atrial premature contractions) with normal lung sounds. Abdominal palpation was unremarkable, and rectal palpation revealed moderate to severe, symmetric prostate enlargement. Additionally, the prostate was nonpainful on palpation, and the median prostatic groove was easily palpable. A blood-tinged, serosanguineous discharge constantly dripped from the dog's prepuce during the examination (and throughout the dog's hospital stay). Occasionally, frank blood was seen in the discharge.

Table 3: Urinalysis Results
A complete blood count showed mild hemoconcentration and thrombocytopenia (Table 1). A serum chemistry profile revealed mild azotemia, hypercalcemia, and hypercholesterolemia (Table 2). Complete urinalysis of a urine sample obtained by cystocentesis revealed microscopic hematuria but no bacteria or neoplastic cells (Table 3). The urine was adequately concentrated, suggesting prerenal azotemia. A bacterial culture from this sample produced only light growth of Staphylococcus species (colony count about 2,000/ml). The result indicated a contaminant, so sensitivity and susceptibility testing was not done.

Figure 1: A lateral radiograph of the dog's caudal abdomen obtained on admission revealing marked prostatomegaly (black arrow). The white arrow indicates the cranially displaced urinary bladder.
An abdominal radiographic examination showed moderate prostatomegaly with no evidence of sublumbar lymph node enlargement (Figure 1). Additionally, mild hepatosplenomegaly was noted. A uniformly enlarged prostate of mostly uniform echotexture was seen on abdominal ultrasonographic examination. One small prostatic cyst was seen dorsal to the urethra (Figure 2). Splenomegaly was noted, but the splenic architecture was of uniform echotexture. The liver and both kidneys appeared to be normal. Despite an extensive evaluation, no evidence of a retained abdominal testicle was found. An ultrasound-guided fine-needle aspiration of the prostate was performed, and microscopic review of this sample revealed only normal prostatic epithelial cells with no evidence of neoplasia or inflammation.