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Katharine M. Simpson Department of Veterinary Clinical Sciences, Center for Veterinary Health Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078.

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 DVM, MS, DACVIM
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Robert N. Streeter Department of Veterinary Clinical Sciences, Center for Veterinary Health Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078.

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Corey R. Wall Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843.

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Mee Ja M. Sula Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078.

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Melanie A. Breshears Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078.

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 DVM, PhD, DACVP

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History

A 2-year-old Boer goat buck was evaluated at the Veterinary Teaching Hospital at Oklahoma State University because of straining to urinate for 24 hours. The goat had been treated twice in the past 4 months by another veterinarian for urolithiasis. Three months previously, the owner had noticed a swelling in the perineal region.

At the time of hospital admission, the goat postured to urinate and vocalized while straining but was unable to void urine. A distended urinary bladder was identified on deep abdominal palpation. Palpation of the perineal region revealed a large, turgid, fluid-filled structure approximately 4 cm wide and 10 cm long that extended from the proximal aspect of the sigmoid flexure to 6 cm distal to the anus. The urethral process was absent.

Neutrophilic leukocytosis (28,600 WBCs/μL [reference range, 7,000 to 15,000 WBCs/μL]; 26,598 neutrophils/μL [reference range, 1,800 to 4,500 neutrophils/μL]), azotemia (creatinine concentration, 6.3 mg/dL [reference range, 0.6 to 1.6 mg/dL]; BUN concentration, 84 mg/dL [reference range, 5 to 24 mg/dL]), and hyperkalemia (5.9 mEq/L [reference range, 3.4 to 5.5 mEq/L]) were detected on CBC and serum biochemical analysis. Retrograde urethral catheterization was attempted but was unsuccessful.

Although irreparable urethral damage may have already occurred and the prognosis for return to breeding soundness was guarded, treatment was elected because of the genetic value of the goat. A tube cystostomy was performed while the goat was under general anesthesia. No uroliths were found during cystostomy tube placement. The wall of the urinary bladder was markedly thickened, and a large amount of cellular debris was removed from the bladder. Urinalysis revealed hematuria with no urine crystals present. Medical treatment was initiated with IV fluid therapy, parenteral antimicrobial administration, and ammonium chloride PO. Two days after cystostomy tube placement, the goat began dripping urine from its prepuce but active urination was not seen.

Ten days after the cystostomy tube was placed, the goat was anesthetized and positive-contrast cystography and normograde urethrography were performed. The urinary bladder was slowly filled through the cystostomy tube with ioversola (240 mg of iodine/mL) diluted to obtain a 15% solution of contrast medium (Figure 1).

Figure 1—
Figure 1—

Right lateral radiographic views of the pelvic and perineal region obtained to evaluate the urinary bladder and pelvic urethra (A) and the penile urethra within the sigmoid flexure (B) following positive-contrast cystography and normograde urethrography performed through a cystostomy tube in a 2-year-old Boer goat buck evaluated because of stranguria.

Citation: Journal of the American Veterinary Medical Association 243, 10; 10.2460/javma.243.10.1395

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page

Diagnostic Imaging Findings and Interpretation

The urinary bladder and urethra contain contrast medium. On the positive-contrast cystogram, the inherent lack of abdominal detail does not allow for the delineation of the serosal margins of the urinary bladder; therefore, the bladder wall thickness is not radiographically assessable. The varied opacity of the urinary bladder is the result of settling of the contrast medium to the dependent aspects of the urinary bladder (Figure 2). The filling defect within the urinary bladder is indicative of the inflated balloon of the cystostomy tube.

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. A—The filling defect in the urinary bladder (arrowheads) is attributable to the inflated balloon of the cystostomy tube. Between the portion of the urethra within the sigmoid flexure and the pelvic urethra, a dilated region is present (white arrows). Within the dilated structure, multiple irregularly shaped filling defects (black arrows) are evident; the nature and shape of these filling defects are consistent with mucosal proliferation, blood clots, or calculi. B—The dilated region of the urethra (white arrows) is evident. Notice that several of the filling defects are smoothly marginated and round (black arrows), which is consistent with air bubbles. Within the sigmoid flexure, there are regions of the penile urethra that are narrowed or have no filling with contrast medium (arrowheads). Linear metallic opacities represent surgical skin staples.

Citation: Journal of the American Veterinary Medical Association 243, 10; 10.2460/javma.243.10.1395

On the positive-contrast urethrogram, a large, smoothly marginated, dilated region of the urethra is evident between the sigmoid flexure of the penis and the pelvic urethra. Within the dilated structure, multiple irregularly shaped filling defects are present (Figure 2). The irregular nature and shape of most of these filling defects is most consistent with mucosal proliferation, blood clots, or calculi. However, several of the filling defects within the dilated structure are smoothly marginated and round; these specific filling defects are consistent with air bubbles.

Immediately proximal to the dilated structure, there is a region of the pelvic urethra that contains a linear filling defect (Figure 3), presumably as a result of a mucosal fold or a leading edge of the dilated structure. On positive-contrast normograde urethrography, the urethral recess is normal in appearance. Distal to the dilated structure and throughout the penile urethra within the sigmoid flexure, there are regions that are narrow or contain no contrast medium.

Figure 3—
Figure 3—

An additional right lateral radiographic view of the pelvic and perineal region of the same goat as in Figure 1 obtained following positive-contrast normograde urethrography. The region of an anatomically normal urethral recess (arrows) is delineated. Notice the linear filling defect (arrowhead) proximal to the dilated region of the urethra. Linear metallic opacities represent surgical skin staples.

Citation: Journal of the American Veterinary Medical Association 243, 10; 10.2460/javma.243.10.1395

Chronic urethral trauma secondary to urolithiasis was the most likely explanation for the observed urethral changes within the sigmoid flexure. A traumatic periurethral diverticulum or urethral pseudodiverticulum with inflammatory polyps was considered to be the most likely cause of the large dilated tubular structure observed proximal to the penile sigmoid flexure. Ultrasonography of the perineum was performed and revealed a large structure filled with fluid of mixed echogenicity, suggesting moderately cellular fluid, but was not able to reliably differentiate between a periurethral diverticulum and urethral pseudodiverticulum.

Treatment and Outcome

Semen collection from the goat was attempted but was unsuccessful. Surgical options for permanent urinary diversion were offered, but the owners opted to have the goat euthanatized. Urethral diverticulectomy or urethrostomy was not considered viable options in this patient given the proximal location and size of the diverticulum, and the owner's desire for the goat to be a natural breeding buck.

Necropsy revealed a large periurethral dilatation that segmentally interrupted the urethral wall and was devoid of urethral mucosa. These findings were most consistent with a urethral pseudodiverticulum. Histologically, the interior surface of the urethral pseudodiverticulum was overlain with a diffuse fibrinocellular layer of necrotic debris; this likely accounted for the irregularly shaped filling defects noted within the diverticulum on the positive-contrast urethrogram. On histologic examination of multiple sections of the penile urethra within the sigmoid flexure, the urethral lumen was moderately constricted by dense fibrous connective tissue. This was consistent with the radiographic finding of regions of the penile urethra that appeared narrowed or lacked contrast medium.

Comments

The urethral recess is a normal structure found in male goats that extends from the proximal portion of the penile urethra in a caudodorsal direction at the level of the ischial arch.1 It is oval and approximately 0.5 cm in depth, and in a clinical setting, the urethral recess is a serious impediment to passage of urethral catheters into the urinary bladder.1 In the goat of the present report, a urethral recess that was normal in appearance was evident on the positive-contrast urethrogram, ruling out congenital or acquired urethral recess dilatation.

In humans, diverticula arising from the urethra are categorized on the basis of the state of the suburethral fascia. Dilatations in which the suburethral fascia remains intact are classified as urethral diverticula, whereas dilatations that interrupt the fascia underlying the urethra are classified as urethral pseudodiverticula.2 Urethral pseudodiverticula are typically traumatic in origin, as is likely true of the case described in the present report in which the dilatation formed secondary to urethral rupture and urine leakage into the periurethral tissues accompanied by fibrinonecrotic diverticulitis and segmental periurethral fibrosis.

Reports of congenital or acquired urethral diverticula in male animals are rare and in ruminants are limited to congenital anomalies.3 Urethral recess dilatation has been infrequently described in cattle but is typically located immediately caudal to the ischial arch in the region of the urethral recess.4 In the goat of the present report, because of the distad nature of the dilated structure, evidence of strictures in the distal portion of the penile urethra, and histologic findings that included segmental interruption of the urethral wall and absence of urethral mucosa within the lumen of the dilated space, the radiographic findings were consistent with an acquired urethral pseudodiverticulum subsequent to obstructive urolithiasis.

a.

Optiray 240, Mallinckrodt Inc, Hazelwood, Mo.

  • 1. Garrett PD. Urethral recess in male goats, sheep, cattle, and swine. J Am Vet Med Assoc 1987; 191:689691.

  • 2. Leng WW, McGuire EJ. Management of female urethral diverticula: a new classification. J Urol 1998; 160:12971300.

  • 3. Purohit S, Gahlot TK. Urethral diverticulectomy in male kids: review of 5 cases. Vet Pract 2007; 8:5556.

  • 4. Anderson DE, Wallace CE, Williamson L, et al. Urethral recess dilatation in a Charolais-cross bull calf. Can Vet J 1993; 34:234235.

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