Abstract
A five-year-old castrated male elk (Cervus elaphus) was examined because of a five-hour history of depression, anorexia, abdominal straining, and bruxism. The elk had been maintained in a three-hectare lot with a diet of cubed alfalfa hay, native grass hay, and a pelleted supplement. Water and a trace mineral block were available ad libitum. The elk was restrained in a 0.75×2 m chute for examination. Stranguria was noted with small amounts of red-brown urine released from the urethral orifice during straining. Frank blood was apparent in a free-catch urine sample. Blood was drawn for hematologic and serum biochemistry analyses. All serum biochemical and hematologic values were within normal reference ranges for adult elk.1 For further examination, anesthesia was induced by hand-injection of carfentanil citrate (Wildnil, Wildlife Pharmaceuticals Inc., Fort Collins, CO; 20 µg/kg IM) and the elk was placed in lateral recumbency. Attempts to fully extend the distal tip of the penis for visual inspection and palpation were unsuccessful due to the elk’s muscle tone. Transrectal abdominal palpation revealed a large distended urinary bladder.
Based on the history and physical examination findings, urethral obstruction was diagnosed, and the elk was treated by perineal urethrostomy. The sigmoid flexure of the penis was palpated caudal to the scrotal remnant and an 8-cm skin incision was made along the ventral midline directly over the penis at this location. The sigmoid flexure was identified, bluntly dissected free of subcutaneous tissue, and exteriorized through the skin incision. The urethra was distended, but no calculi were visible or palpable at any point along the 12-cm length of exposed penis. The dorsal caudolateral portion of the penis was attached to the skin at the dorsal end of the incision with a simple interrupted suture of 2-0 monofilament polyglyconate on each side of the urethra. The needle was passed through the layers of the corpus spongiosum without penetrating the urethral mucosa. Once the penis was secured to the skin, it was transected leaving an 8-cm stump proximally and intact attachments of the retractor penis muscles distally. Bleeding was minimal due to occlusion of the corpus cavernosum blood supply by the dorsal sutures. The urethra was then incised longitudinally at the proximal stump. A #8 French urinary catheter was passed through the urethra toward the urinary bladder. After initial resistance, the catheter was passed successfully into the bladder and clear yellow urine flowed through. A urine sample was collected for evaluation but was not collected sterilely for culture. The penis was secured to the skin and the remainder of the skin incision was closed routinely. The urinary catheter was removed.
The carfentanil immobilization was antagonized with naltrexone HC1 (Trexonil, Wildlife Pharmaceuticals Inc., Fort Collins, CO; 100 mg/mg carfentanil; 25% IV, 75% SC) and the elk recovered uneventfully. Within 15 minutes of surgery, the elk voided large amounts of urine through the perineal urethrostomy without evidence of straining. Urinalysis was unremarkable; urine pH was 9.0 and specific gravity was 1.009. No crystalluria was observed.
Mild intermittent bleeding from the perineal urethrostomy site lasted for 10 days after surgery. Antibiotic treatment was initiated at the time of surgery with penicillin G benzathine and penicillin G procaine (Dura-Pen, Durvet, Inc., Blue Springs, MO; 22,000 IU/kg) administered every 48 hours for two treatments. Phenylbutazone (Butatabs-E, Burns Veterinary Supply, Rockville Centre, NY; 4 mg/kg) was administered PO on postoperative days one and three for analgesia. Clostridium spp. bacterin (Ultrabac 7, Smith-Kline Beecham Corp, West Chester, PA; 4 ml SC) was administered at the time of surgery. Abdominal pain and stranguria were not observed after surgery and the elk has continued to void urine through the perineal urethrostomy site nine months postoperatively. Although a 10% weight loss occurred over the two-week postoperative period, a return to initial body weight occurred over the following two months without dietary changes.
Discussion
Urethral obstruction has been reported in many domestic species of artiodactylids2,5 and urolithiasis is the most common cause of urinary tract obstruction in these species. The distal aspect of the sigmoid flexure is the most common site for urinary calculus impaction in cattle and is the second most common site for obstruction in sheep and goats.6 Urinary calculi have been documented in white-tailed deer and elk, although urethral obstruction secondary to urolithiasis has not been reported.3,6 Magnesium ammonium phosphate calculi are the most common type of urolith in domestic ruminants while calcium carbonate and calcium oxalate uroliths have been documented in cervids.3,5,6 Phosphatic uroliths are common in animals grazing lush pastures that are high in calcium and oxalate content. Decreased water intake may also be calculogenic. The elk’s ration was not high in calcium or oxalates, and water intake appeared to be adequate. However, the animal’s ration was formulated into wafers, and this condensed food source may have contributed to calculogenesis. Early castration is also thought to influence urethral obstruction as average urethral luminal diameter is smaller in male ruminants that are castrated prior to sexual maturity.6 This elk was castrated at less than six-months-old, which may have contributed to a decreased urethral luminal diameter and consequent urethral obstruction.
Captive Artiodactylids with urethral obstruction have been euthanatized without specific treatment because of the perception that this condition bears a poor prognosis.2 Reports on the use of surgical treatment of urethral obstruction in nondomestic Artiodactylids are rare, although surgical procedures including perineal urethrostomy, cystotomy, and urethral process amputation are used routinely to correct urethral obstruction in domestic ruminants.4 While the cause of this elk’s urethral obstruction remains undetermined, early diagnosis and treatment have allowed an excellent prognosis in this animal. Minimal postoperative treatment was required, and the urinary obstruction has not recurred.
Literature Cited
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