Introduction

A 3-year-old 7.5-kg (16.5-lb) neutered male domestic shorthair cat was presented to the emergency service of a veterinary teaching hospital approximately 48 hours following presumed vehicular trauma. The cat had been taken to another emergency veterinary hospital immediately following injury, where it was found to be bleeding from a small wound on the right pelvic limb and to have a limp tail. On examination of the cat at the primary care facility 2 days later, tail tone and sensation were absent and sacrocaudal joint luxation was diagnosed radiographically (Figure 1). The owners reported that urination by the cat had not been witnessed since the incident. The cat was subsequently referred to the veterinary teaching hospital.

Lateral (A) and ventrodorsal (B) radiographic views of the caudal aspect of the body of a 3-year-old cat obtained approximately 48 hours following an incident of vehicular trauma. Notice the luxation of the sacrocaudal joint.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Lateral (A) and ventrodorsal (B) radiographic views of the caudal aspect of the body of a 3-year-old cat obtained approximately 48 hours following an incident of vehicular trauma. Notice the luxation of the sacrocaudal joint.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Lateral (A) and ventrodorsal (B) radiographic views of the caudal aspect of the body of a 3-year-old cat obtained approximately 48 hours following an incident of vehicular trauma. Notice the luxation of the sacrocaudal joint.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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On evaluation, the cat was bright and alert with a rectal temperature of 38.2°C (100.7°F), heart rate of 260 beats/min, and respiratory rate of 32 breaths/min. It had a body condition score of 9/9 (obese). A pain reaction was noted during palpation of the caudal portion of the abdomen, and the urinary bladder was moderately enlarged and turgid. Moderate bruising of the right inguinal region and swelling over the base of the tail were evident. The tail had absent tone, motor function, and nociception. The remainder of the neurologic and physical examination findings were considered normal. Clinicopathologic analyses revealed azotemia with a BUN concentration of 35 mg/dL (reference range, 7.5 to 30 mg/dL) and serum creatinine concentration of 2.3 mg/dL (reference range, 0.6 to 1.2 mg/dL); serum potassium concentration was within reference range (4.6 mmol/L; reference range, 3.4 to 4.8 mmol/L). An abbreviated abdominal ultrasonographic examination revealed no free abdominal fluid.

The cat was sedated with butorphanol tartrate for attempted placement of a urethral catheter. The catheter could not be passed into the urinary bladder, and when the catheter was flushed, the subcutaneous space in the perineal region was noted to expand. Decompressive cystocenteses were performed overnight until the cat could be anesthetized for further evaluation the following day. During anesthesia, a 3.5F polyurethane tomcat urethral catheter^a was successfully placed into the urinary bladder with digital guidance via the rectum. Radiography and retrograde contrast urethrocystography (with instillation of a total of 12 mL of iohexol [350 mg of iodine/mL] through a 3.5F catheter inserted in the distal portion of the urethra) were performed, which revealed a urethral tear at the level of the ischiatic tuberosity with leakage of urine into the subcutaneous tissues surrounding the left pelvic limb and lumbar region (Figure 2). There was no leakage into the peritoneal cavity. The urethral catheter with a closed collection system was left in place for 7 days in an attempt to promote development of a tissue scaffold for primary healing. Following removal of the urethral catheter, retrograde contrast urethrocystography was repeated, which revealed persistence of the urethral tear. While the cat was under anesthesia, the owner was contacted and given the options of replacement of the urethral catheter for a longer period or surgical treatment; the owner elected surgical management. On the basis of the location of the leakage seen on the contrast urethrocystogram, a perineal urethrostomy was planned during the same anesthetic episode with the intention of excising the tear along with the distal portion of the urethra.

Retrograde contrast urethrocystogram (A) and radiographic view (B) of the caudal aspect of the body of the cat in Figure 1. On the urethrocystogram, notice a urethral tear at the level of the ischiatic tuberosity. Extensive leakage of contrast medium in the subcutaneous tissues surrounding the left pelvic limb, left flank, and perineal region is evident.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Retrograde contrast urethrocystogram (A) and radiographic view (B) of the caudal aspect of the body of the cat in Figure 1. On the urethrocystogram, notice a urethral tear at the level of the ischiatic tuberosity. Extensive leakage of contrast medium in the subcutaneous tissues surrounding the left pelvic limb, left flank, and perineal region is evident.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Retrograde contrast urethrocystogram (A) and radiographic view (B) of the caudal aspect of the body of the cat in Figure 1. On the urethrocystogram, notice a urethral tear at the level of the ischiatic tuberosity. Extensive leakage of contrast medium in the subcutaneous tissues surrounding the left pelvic limb, left flank, and perineal region is evident.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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The cat was placed in dorsal recumbency with the pelvic limbs pulled cranially. At this point, the urethral catheter had been removed and could not be replaced beyond the urethral tear. An elliptical incision was made around the prepuce, and the urethra was dissected free from its attachments. The ischiocavernosus muscles did not require transection because they were avulsed from their ischial attachments, presumably as a result of the original traumatic event. The retractor penis muscle was sharply transected, and dissection was continued until the bulbourethral glands were encountered. A deep subcutaneous pocket of fluid was identified to the left of the perineum extending toward the left pelvic limb. A 1-mm-long defect on the ventral aspect of the urethra just distal to the caudal aspect of the ischial symphysis and proximal to the bulbourethral glands was determined to be actively leaking; further exploration revealed the original defect to be 4 mm in length in a craniocaudal orientation and encompassing approximately 50% of the urethral circumference, with local steatitis and evidence of a thin film of fibrous tissue along approximately 3 mm of the defect. A 3.5F red rubber catheter was passed beyond the tear into the urinary bladder. The urethral defect was determined to be too proximal to permit standard perineal urethrostomy. Stricture development was considered likely if primary repair without augmentation were to be attempted because direct apposition of the large defect would have resulted in a very narrow urethral lumen as a result of loss of urethral tissue. During the procedure, the owner was contacted to discuss options and elected augmented urethroplasty with perineal urethrostomy because of concerns that the cat's obese body condition would lead to complications associated with prepubic urethrostomy.

During the same anesthetic episode, a rectangular section of single-layer porcine SIS^b was cut to fit over the urethral tear, overlapping the edges of the tear by approximately 1 mm. The graft was sutured over the urethral serosa with 5-0 poliglecaprone 25 suture material in a simple interrupted pattern on one side to hold the SIS in place; a simple continuous pattern was used for the remaining closure because of increasing difficulty identifying the other side of the defect as the SIS was sutured over it. Suturing was performed over the urethral catheter to prevent accidental occlusion of the urethra. Perineal urethrostomy was then performed distal to the defect, with the urethral mucosa sutured to the perineal skin with 4-0 polypropylene suture material in an interrupted figure-eight suture pattern. Tail amputation was then performed because of continued and likely permanent lack of nociception. Postoperative retrograde contrast urethrocystography revealed resolution of the urethral tear (Figure 3). A 5F urethral catheter was left in place for 5 days. Repeated retrograde contrast urethrocystography at the time of catheter removal indicated continued patency of the urethra with no leakage of contrast medium.

Retrograde contrast urethrocystogram obtained immediately after the cat underwent urethroplasty augmented with a single-layer porcine SIS graft and perineal urethrostomy. The urethral tear has been resolved. Routine tail amputation was also performed.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Retrograde contrast urethrocystogram obtained immediately after the cat underwent urethroplasty augmented with a single-layer porcine SIS graft and perineal urethrostomy. The urethral tear has been resolved. Routine tail amputation was also performed.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Retrograde contrast urethrocystogram obtained immediately after the cat underwent urethroplasty augmented with a single-layer porcine SIS graft and perineal urethrostomy. The urethral tear has been resolved. Routine tail amputation was also performed.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Approximately 2 days following removal of the urethral catheter, the cat developed stranguria. Repeated retrograde contrast urethrocystography revealed a urethral stricture at the site of the previous repair (Figure 4). Balloon dilation was performed with a 6 X 2-cm balloon^c and a pressurized injector during contrast and fluoroscopic monitoring. Following dilation of the stricture, an 8F red rubber catheter could be easily passed into the urethra, beyond the stricture, and into the urinary bladder; resolution of the stricture was confirmed fluoroscopically. Microbial culture of a urine sample collected at this time yielded no growth. A 5F red rubber catheter attached to a closed collection system was left in place for 4 days. Following removal of the catheter, the cat was urinating well and was discharged from the hospital. Treatments at home included prazosin (0.1 mg/kg [0.045 mg/lb], PO, q 12 h) and buprenorphine (0.02 mg/kg [0.009 mg/lb], buccally, q 8 h). On follow-up examination 3 weeks later, the cat was urinating normally and treatments were discontinued at that time.

Series of retrograde contrast urethrocystograms acquired 2 days after the cat underwent urethroplasty and perineal urethrostomy. A—A urethral stricture just distal to the ischiatic tuberosity at the site of the urethroplasty is evident. B—A balloon is positioned at the site of urethral stricture for dilation. C—Immediately following balloon dilation, resolution of the urethral stricture is apparent.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Series of retrograde contrast urethrocystograms acquired 2 days after the cat underwent urethroplasty and perineal urethrostomy. A—A urethral stricture just distal to the ischiatic tuberosity at the site of the urethroplasty is evident. B—A balloon is positioned at the site of urethral stricture for dilation. C—Immediately following balloon dilation, resolution of the urethral stricture is apparent.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Series of retrograde contrast urethrocystograms acquired 2 days after the cat underwent urethroplasty and perineal urethrostomy. A—A urethral stricture just distal to the ischiatic tuberosity at the site of the urethroplasty is evident. B—A balloon is positioned at the site of urethral stricture for dilation. C—Immediately following balloon dilation, resolution of the urethral stricture is apparent.

Citation: Journal of the American Veterinary Medical Association 258, 2; 10.2460/javma.258.2.186

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Approximately 4 weeks after surgical management of the urethral stricture, the cat was evaluated because of mild stranguria; the urinary bladder was palpably small, and an 8F red rubber urethral catheter could be easily passed. Urinalysis was not performed at that time. Prazosin was again prescribed at the previous dosage.

Approximately 6 weeks later (10 weeks after the first balloon dilation procedure), the cat was evaluated because of hematuria that had been waxing and waning over a 3-week period. The owner stated that the cat had not had noticeable stranguria at home. Urinalysis revealed a moderate number of bacteria, and Staphylococcus pseudintermedius and Staphylococcus aureus were grown on culture of a urine sample. Administration of amoxicillin–clavulanic acid (23 mg/kg [10.45 mg/lb], PO, q 12 h) was started on the basis of the antimicrobial susceptibility test results. The cat had frequent episodes of stranguria during hospitalization, and retrograde contrast urethrocystography was performed. A urethral stricture was detected at the site of the previous tear repair and balloon dilation, and urethroscopy revealed circumferential proliferative tissue surrounding the stricture site. Balloon dilation of the urethral stricture as previously described was repeated, and an 8F red rubber catheter was passed readily past the stricture site. Approximately 0.5 mL (20 mg) of triamcinolone solution (40 mg/mL) was instilled on the uroepithelial surface through a catheter at the site of prior stricture to attempt to minimize the recurrence of stricture formation.

Two months following the second balloon dilation procedure, the cat had occasional leakage of small amounts of urine, but typically would urinate large volumes in the litter box with no evident stranguria. Prazosin was prescribed, and administration of the drug was gradually tapered completely. Six months following the second balloon dilation procedure, the cat was urinating normally and not receiving any medications. Eighteen months following the second balloon dilation procedure, the owner was contacted and reported that the cat was continuing to urinate normally and they were very satisfied with the cat's condition.

Discussion

Urethral trauma is relatively common in cats, and iatrogenic injury from attempts at urethral catheterization and vehicular trauma are the most common causes.^1,2 Urethral healing over an indwelling catheter is possible in many cats in which catheterization is achievable, particularly cats with smaller-sized defects.³ Tube cystostomy in conjunction with urethral catheterization may be considered to temporarily divert urine away from the urethra.⁴ Given the variations in urethral defect size and conformation and the inability to determine the size without direct observation of the lesion, it is difficult to accurately predict the duration of urethral catheterization that would be necessary to allow sufficient healing prior to catheter removal; in 1 study³ of 11 cats with traumatic urethral rupture, durations of urethral catheterization ranged from 5 to 14 days.

Hospitalization time and incidence of ascending iatrogenic urinary tract infections associated with prolonged urethral catherization in dogs and cats may be reduced with primary repair of urethral defects.^2,3 In large urethral defects with major tissue loss, primary repair or resection and anastomosis of the urethra may result in unacceptable narrowing of the urethral lumen or not be possible. Multiple options for surgical diversion of the urinary tract following urethral tears in cats have been reported, including perineal urethrostomy, transpelvic urethrostomy, prepubic urethrostomy, and cystostomy tube placement.^3,4,5,6,7 Perineal urethrostomy is a widely used procedure that is generally well tolerated by cats, with urethral stricture and urinary tract infections being the most common complications.⁵ However, tears proximal to the bulbourethral glands may not be amenable to this procedure without urethroplasty. Although transpelvic urethrostomy may allow for anastomosis with the skin more proximal to the bulbourethral glands, compared with a standard perineal urethrostomy, defects extending > 2 cm proximal to the bulbourethral glands may not be amenable to this approach. Prepubic urethrostomy may be considered in those cases but may be associated with higher rates of incontinence or peristomal skin irritation, compared with outcomes of perineal urethrostomy.^6,7

Small intestinal submucosa has been used for the augmentation of various surgically treated defects in both human and veterinary medicine. It is prepared by removing the mucosal and seromuscular layers of portions of the small intestine, leaving behind the

extracellular matrix of the submucosa.⁸ The collagen-rich SIS contains growth factors, allows for ingrowth of the specific tissue in which it is used, and is not associated with graft rejection in xenogeneic applications.⁹ Experimentally, SIS has been shown to act as a temporary scaffold in canine urinary bladders with rapid host tissue remodeling, which results in tissue that is histologically indistinguishable from normal urinary bladder tissue within 15 months.⁸ One clinical veterinary report¹⁰ describes SIS-augmented urethroplasty with balloon dilation to repair a urethral stricture that developed secondary to inadvertent prostatectomy in a dog. To the authors’ knowledge, the present case represented is the first reported use of SIS to augment urethroplasty in a cat. Although the procedure was tolerated well by the cat, 2 postoperative episodes of dysuria resulting from urethral stricture occurred and were successfully treated with 2 procedures involving balloon dilation and a single application of triamcinolone solution on the uroepithelial surface at the stricture site.

The urethral mucosa is capable of healing within 7 days if a continuous strip is preserved and urine leakage is avoided.^3,11 Although evidence of partial healing was present at the time of surgery in the cat of the present report, placement of a urethral catheter for 7 days was not sufficient to achieve complete healing. It is unclear whether the subsequent use of SIS in this cat contributed to healing primarily by providing a growth factor–rich scaffold or diverting urine away from the defect to allow it to heal more effectively. Additionally, a urethral catheter was placed after application of the SIS, which may have contributed to healing of the defect. Urethral catheterization in cats is not without the potential for adverse effects such as iatrogenic worsening of urethral trauma, contribution to the development of urinary tract infections, or premature dislodgement of the catheter.³ In a study³ evaluating medical management of urethral ruptures with urethral catheterization with or without concurrent cystostomy tube placement, urethral strictures developed in 3 of 11 cats. Additionally, the cost of prolonged hospitalization must be considered when deciding between medical and surgical management of urethral trauma in cats.

Regardless of species, stricture is a common complication following urethral surgery. Careful attention to urethral mucosal apposition and the prevention of urine leakage into the surrounding tissues are important techniques for the prevention of strictures.¹¹ In the cat of the present report, it was possible that the combination of a lack of direct mucosal apposition with a history of urine leakage around the traumatized urethra increased the risk of fibrosis and subsequent stricture development. Historically, urethral strictures in cats have been treated with resection of the stricture and anastomosis of healthy portions of the urethra.³ Balloon dilation has been described for successful treatment of urethral strictures in 2 dogs^10,12 but has not been previously described in cats, to the authors’ knowledge. For this cat, a prepubic urethrostomy was considered suboptimal because of its obese body condition and the associated concern for peristomal urine leakage and irritation.⁷ Given the location of the tear, a transpelvic urethrostomy may have been an alternative option but was not performed because of concern that the proximal aspect of the tear would become incorporated into the urethrocutaneous anastomosis. Use of torn mucosa for the anastomosis may increase the risk of complications if poor healing of the mucocutaneous anastomosis occurs. For the cat of the present report, it was possible that transpelvic urethrostomy would have allowed anastomosis proximal to the torn portion of mucosa, but urethroplasty with SIS augmentation was considered a viable alternative. Use of urethral stents in cats has also been reported^13,14 and could be considered if the stricture were to redevelop in the cat of the present report. Owing to financial constraints, the owner declined urethral stenting; therefore, a second attempt at balloon dilation was performed. With strictures of other structures such as the nasopharynx or rectum, cats tend to respond well to balloon dilation with few treatments required^15,16; therefore, a second balloon dilation was considered reasonable in the case described in the present report.

Application of triamcinolone solution to the mucosa of the stricture site following balloon dilation as a means of decreasing recurrent stricture formation has been attempted in the rectum and esophagus of cats and dogs, respectively, with no reported complications.^16,17 In a study¹⁸ to evaluate urethral diameter in rabbits following iatrogenic trauma, injection of 40 mg of triamcinolone solution to the traumatized urethra resulted in a significantly larger urethral diameter, compared with that achieved following irrigation with saline solution. Although the exact mechanism of action is unknown, triamcinolone is believed to reduce fibrosis formation by increasing collagenase production and decreasing collagenase inhibitors.¹⁸ Given its ease of application and low reported risk of adverse effects, instillation of triamcinolone at the time of balloon dilation can be considered to help prevent stricture reformation.

The cat of the present report ultimately had an excellent quality of life, as do cats that undergo perineal urethrostomy without a urethral tear, and the owners were very satisfied with the outcome nearly 2 years after the initial hospitalization period. Use of SIS as a component of urethroplasty may be a viable surgical augmentation for treatment of urethral tears that have failed to heal with conservative management by means of urethral catheterization in cats. Owners should be advised of the potential for postoperative stricture development that may require additional treatment.