Porcine Small Intestinal Submucosa Augmentation Urethroplasty and Balloon Dilatation of a Urethral Stricture Secondary to Inadvertent Prostatectomy in a Dog
A 10-month-old, male German shepherd dog experienced inadvertent prostatectomy during cryptorchidectomy. Cystourethral anastomosis was performed 1 day later. The dog developed stranguria and incontinence. A proximal urethral stricture was diagnosed with a contrast urethrogram 5 weeks later. Urethral augmentation with an onlay graft of porcine small intestinal submucosa was performed. Urinary diversion was accomplished with a urethral catheter followed by a cystostomy tube. The stricture recurred over the next 6 weeks. Three urethral balloon dilatations were performed 3 days apart, with the third attempt resulting in expansion of the stricture. Twenty-two months postdilatation, the dog intermittently urinated with a steady stream and had mild to moderate urinary incontinence.
Introduction
Stricture is the most common complication of urethral trauma in small animals and is most commonly treated with either resection and anastomosis or urethral diversion via urethrostomy.1 Urethral augmentation with porcine small intestinal submucosa (SIS) onlay grafts has been successfully used to treat urethral strictures in humans but has not been previously reported in the dog.2,3 Similarly, balloon dilatation is considered a safe and effective treatment for urethral strictures in humans, but only three instances of this procedure have been reported in dogs.4–7
The purpose of this report is to describe the management of a dog with urethral stricture and urinary incontinence secondary to inadvertent complete prostatectomy during cryptorchidectomy. Urethral augmentation with porcine SIS and multiple balloon dilatations were used to restore urethral patency.
Case Report
A 10-month-old, 34-kg, castrated male German shepherd dog was evaluated at the Washington State University Veterinary Teaching Hospital because of a 4-week history of stranguria, urinary incontinence, and a heart murmur. A celiotomy had been performed for bilateral cryptorchidism 5 weeks prior to presentation. After removal of the presumptive testes, hemorrhage was noted. The bleeding appeared to be from a defect in the urinary bladder wall (likely iatrogenic in origin), and the defect was sutured closed. For the next 24 hours, the dog was anuric. A urinary catheter was passed, and no urine was obtained. A second celiotomy was performed. The urethra was found to be avulsed from the bladder. The bladder was markedly distended with urine, because the outflow path had been closed during the first surgery. Cystourethral anastomosis was performed. A heart murmur was first heard 1 day after this second surgery. During the next 4 weeks, the dog was managed on amoxicillin-clavulanic acida (11 mg/kg body weight per os [PO] q 24 hours) and phenylpropanolamineb (1.5 mg/kg PO q 24 hours), as well as antioxidants, vitamins, fish oil supplement, and homeopathic medicines. The owner catheterized the dog’s urethra four times daily. Description of the procedure by the owner suggested that the catheter was not being inserted all the way into the bladder each time. The owner reported that the dog could voluntarily urinate but produced only a very small stream. At times, the dog dribbled urine, and manual bladder expression by the owner and veterinarian was difficult.
A physical examination and abdominal palpation at the time of referral to the Washington State University Veterinary Teaching Hospital revealed an enlarged, firm bladder. Urine dribbled from the penis intermittently. The integument around the prepuce was erythematous. The dog had a bilateral, grade VI/VI, holosystolic machinery murmur and palpable thrill. The murmur had a regurgitant property on the right and an ejection quality on the left. The point of maximal intensity was over the right heart apex.
A complete blood count revealed a mild leukocytosis (14,000 white blood cells/μL, reference range 5800 to 11,700 cells/μL); mature neutrophilia (8680 cells/μL, reference range 3000 to 7100 cells/μL); monocytosis (1540 cells/μL, reference range <800 cells/μL); eosinophilia (1120 cells/μL, reference range <100 cells/μL); and a mild normocytic, normochromic anemia (5.05 × 106 red blood cells/μL, reference range 5.6 to 8.5 × 106 cells/μL; packed cell volume 35%, reference range 38% to 59%). Serum biochemical analysis showed a mildly elevated blood urea nitrogen (BUN) concentration (32 mg/dL, reference range 9 to 27 mg/dL) and normal creatinine concentration. Urine from a catheterized sample was isosthenuric (specific gravity 1.008) with trace protein and 3+ hemoglobin. Aerobic and anaerobic urine cultures were negative. Tricuspid regurgitation and mild subaortic stenosis were identified with an echocardiogram performed by a veterinary cardiologist.
Intravenous pyelography (IVP) with 2.9 mL/kg of an iodinated contrast solutionc and retrograde negative contrast urethrocystography with 4.4 mL/kg of air were performed under general anesthesia with the following findings: delayed vascular nephrogram and pyelogram in both kidneys; bilateral renal pelvic and ureteral dilatation; poor peristaltic activity and poor filling in the left ureter; normal cystogram; focal stricture (approximately 3 mm long) at the trigonal/urethral junction; and mild dilatation of the pelvic urethra distal to the stricture [Figure 1A].
Two days later, surgical exploration via ventral celiotomy was performed. Ampicillind (20 mg/kg intravenously q 90 minutes) was administered intraoperatively. During the approach, biopsies of the skin and right inguinal lymph node were taken and submitted for histopathology because of marked peripreputial inflammation associated with the previous incision. The skin was also submitted for culture. Abnormal intraabdominal findings included a 4 × 4-inch gauze sponge wrapped in omentum; a right retained testicle; and extensive fibrous adhesions between the bladder neck, proximal urethra, and body wall. The prostate gland was not found. The urinary bladder was moderate to large in size and flaccid. Both kidneys were soft and abnormally shaped, although they were normal in size. Several large vessels were seen adjacent to the right and left kidneys, reminiscent of multiple portosystemic shunts. Bilateral hydroureters were 1 cm in diameter and tortuous. Liver biopsies were also taken to potentially determine the cause of the large perirenal vessels, and the right testicle was removed routinely. Liver and testicular tissues were submitted for histopathology. The gauze and adherent omentum were removed routinely and submitted for histopathology and culture.
Suture material, purulent exudate, and fibrous material were debrided from the site where the prostate should have been. Excessive resection of fibrous tissue dorsal to the bladder and urethra was avoided because of concerns about further damage to the nerves of micturition. A ventral cystotomy was performed. The bladder mucosa was dark green with raised plaques. Samples were submitted for aerobic and anaerobic culture and histopathology. An 8-French red-rubber catheter was passed approximately 0.5 cm normo-grade from the bladder, where resistance was felt. The cystotomy incision was extended caudally into a ventral urethrotomy. The urethral wall in the strictured area was very thick, and the urethra was surrounded by dense, fibrous tissue. Normal-appearing urethra was seen approximately 2 cm caudal to the bladder neck. A single laminate sheet of porcine SISe was folded into a three-layer, 2 × 4-cm rectangle, and it was sutured to the edges of the caudal bladder incision and entire urethral incision with a simple interrupted pattern of 4–0 polydioxane.f The onlay graft of SIS replaced the ventral 180° of the urethra in the affected area [Figure 2]. The cranial cystotomy incision was closed in standard fashion. The omentum was placed over the bladder and proximal urethra. A 12-French Foley urinary catheter attached to a closed urine collection system was kept in place for 2 weeks, and the dog remained hospitalized.
Histopathological findings included severe necrosuppurative dermatitis; a reactive lymph node; chronic, severe, diffuse testicular degeneration (consistent with cryptorchidism); severe necrosuppurative and ulcerative cystitis; and normal liver. With no evidence of portosystemic shunting in the liver, the significance of the vessels seen adjacent to the kidneys remains unknown. The only positive culture was a Mycoplasma spp. from the urinary bladder. The dog was treated with doxycyclineg (5.9 mg/kg PO q 24 hours) for 10 days. The doxycycline was started 16 days after the cystotomy/SIS surgery.
Retrograde contrast cystourethrograms were performed by partially backing out the urethral catheter 8 and 14 days postoperatively [Figures 1B, 1C]. On day 8 postcystotomy, the length of urethral narrowing was increased from the previous examination. In addition, a second, more caudal focal area of narrowing was separated from the first by the previously recognized dilated area. On day 14 postcystotomy, the cranial stricture was unchanged, while the caudal narrowing filled with more contrast than on day 8. No leakage of contrast was identified at the surgical site during either study. The urethral catheter was removed, and a 16-French cystostomy tube with locking looph was placed percutaneously under fluoroscopic guidance. Aerobic and anaerobic urine cultures were negative. The dog was discharged 20 days after the surgery. The owner emptied the bladder via the cystostomy tube four times a day.
Six weeks after SIS urethroplasty, the dog was reexamined. The owner reported the dog was intermittently incontinent, especially when the bladder was full. Stranguria was not reported. Blood urea nitrogen and creatinine concentrations were 32 mg/dL and 1.7 mg/dL, respectively, and urine specific gravity was 1.024. Urine culture was negative for aerobes, anaerobes, and Mycoplasma. The dog was anesthetized for further imaging studies. Compared to the previous examination, IVP showed good opacification of both kidneys, less dilatation of the left renal pelvis, and unchanged dilatation of the right renal pelvis and both ureters. On a cystourethrogram (performed through the cystostomy tube with fluoroscopic guidance), minimal contrastc passed through the urethra at the site where the SIS was previously placed, which was markedly reduced in diameter compared to previous examinations [Figure 1D]. The second, more distal urethral narrowing seen on previous images was no longer present. A 5-French Foley urinary catheter could not be advanced through the stricture. During retrograde contrast urethrography, only a very narrow stream passed through the urethra into the bladder. On ultrasound, the bladder mucosa and wall appeared normal, and circumferential hypoechoic tissue was seen at the presumed level of the urethral surgical site. The stricture seen during the fluoroscopic-guided cystourethrogram could not be distinctly identified with ultrasound. The dog was discharged and prescribed phenoxybenzaminei (0.3 mg/kg PO q 12 hours) while treatment options were considered.
The owner was able to return with the dog 3 months after SIS urethroplasty for further treatment. The BUN and creatinine concentrations were 30 mg/dL and 1.8 mg/dL, respectively, and urine specific gravity was 1.030. Balloon dilatation of the urethral stricture was performed under fluoroscopic guidance on three separate occasions. These procedures were performed 3 days apart using the following technique. With the dog under general anesthesia, retrograde contrast urethrography was performed; contrast materialc was injected through a urinary catheter inserted in the penile urethral orifice to determine the stricture location, length, and urethral dimensions. The catheter was then removed, and a 0.035-inch, angled, floppy-tip hydrophilic guidewirej was inserted into the urethral orifice and advanced into the urethra. The wire easily passed through the stricture and into the bladder. A 5.8-French balloon catheterk was advanced over the guidewire and into the bladder. The balloon was 3.0 cm long with an expanded diameter of 10.0 mm and burst strength of 20 atmospheres. The balloon was positioned such that the radiopaque markers denoting its proximal and distal ends spanned the location of the stricture. The balloon was dilated to about 75% of its potential diameter with a 50% saline/50% contrast mixture to ensure proper balloon placement. The balloon was then dilated for 3 minutes using hand pressure on a syringe. Because a balloon inflation device was not available, the surgeon judged the amount of hand pressure to apply based on the amount of resistance felt and the appearance of the balloon on the fluoroscopic images.
The dog recovered uneventfully following each procedure, and urine evacuation continued through the cystostomy tube. On the first two attempts to dilate the urethra, the balloon appeared fully dilated on each side of the stricture with a significant narrowing in the middle of the balloon [Figure 3A]. During the third treatment, the dilated balloon initially had a narrowed waist at the stricture site, as seen previously. However, the balloon ultimately expanded completely along its entire length and effaced the stricture. Pressure was maintained with the fully dilated balloon for 5 minutes during this treatment [Figure 3B]. A 10-French Foley catheter was then easily passed into the bladder and secured in place.
Over the next 3 days, the dog pulled the catheter out twice; it was replaced the first time but not the second. Without the catheter, the dog was able to produce a small stream of urine and dribbled urine intermittently. Two doses of carprofenl (1.4 mg/kg subcutaneously q 24 hours) were administered each time balloon dilatation was performed. During this time, the dog also received amoxicillin-clavulanic acid (as before) for 10 days, phenoxybenzamine (as before), and bethanecholm (0.13 mg/kg PO q 8 hours) for 7 weeks. The cystostomy tube was removed 10 weeks after placement, which was 10 days after the last balloon dilatation. A minor surgical approach was made to allow direct closure of the bladder because of the relatively large diameter of the cystostomy tube.
Contrast urethrograms with the dog in right lateral recumbency were performed 4 days, 10 days, and 13 months after the third balloon dilatation. The diameter at the urethral stricture site was the same each time, which was wider than the diameter prior to dilatation [Figure 4]. During the contrast urethrogram on the 10th day following balloon dilatation, a ventrodorsal view was also taken. The degree of urethral distention at the stricture level was less than that seen in the lateral plane.
Based on regular urine dipstick tests performed by the owner, the dog was diagnosed with urinary tract infections every 3 to 5 months after balloon dilatation. The infections were successfully treated with either amoxicillin-clavulanic acid or ampicillin. The BUN and creatinine concentrations were 26 mg/dL and 1.3 mg/dL, respectively, 20 months after balloon dilatation.
Twenty-two months after balloon dilatation, the dog was mild to moderately incontinent and wore a diaper. The urine stream produced when the dog postured to urinate varied from a forced dribble to a steady flow that appeared weaker than that achieved by normal dogs. The owner readily expressed urine remaining in the dog’s bladder every 6 to 8 hours, generating a moderate-sized stream. At the time of this report, the dog continued to be regularly examined by a veterinary cardiologist and remained on enalapril (1.7 mg/kg PO q morning and 3.4 mg/kg PO q evening) because of the progression of cardiac disease. The dog was no longer taking any urinary medications at the time of this writing; he was bright, active, and serving as an ambassador for a service dog training program.
Discussion
Inadvertent complete or partial prostatectomy during cryptorchidectomy disrupts urethral continuity. This complication has been reported in five cryptorchid dogs—one of which was euthanized due to necrosis of the bladder trigone and urethra.8,9 The other four dogs recovered fully after surgical repair of the urethral defect. While two dogs had transient urinary incontinence, none had long-term incontinence, and none developed urethral strictures during the follow-up periods, which ranged from 6 months to 2 years. In contrast, stricture and persistent incontinence were both sequelae of inadvertent prostatectomy in the dog of this report.
Excessive tissue trauma, compromised vascular supply, suboptimal mucosal apposition, and the caustic effect of extravasated urine on nonmucosal tissues all increase the risk for urethral stricture formation and were potential contributors to the stricture in the dog of this report.10–12 Specifically, tissue and vascular damage may have been secondary to inadequate surgical exposure (the most likely cause of inadvertent prostatectomy) that necessitated blind palpation for the retained testicles and resulted in traumatic exteriorization of the prostate.9 As in any celiotomy, an incision large enough to allow accurate identification of abdominal structures is recommended during cryptorchidectomy. Precise reapposition of mucosal surfaces was likely difficult when the cystourethral anastomosis was performed 1 day after the urethral avulsion, because mucosa retracts away from the end of the transected urethra.13 Fibrous tissue forms in mucosal gaps, decreasing urethral wall elasticity and leading to luminal narrowing as the fibrous tissue contracts.10,14
The marked amount of reactionary tissue surrounding the bladder and urethra, the reactive inguinal lymph node, and the incisional dermatitis all suggest urine leakage from the anastomosis site. Urine induces severe cellulitis with prolonged contact and predisposes the affected tissue to infection if bacterial contamination occurs.15 Postoperative urine diversion with an indwelling urethral catheter (which was not used in this dog) may have minimized urine extravasation at the cystourethral anastomosis site as well as avoided the potential trauma associated with repeated urethral catheterizations in this dog. Indeed, after experimental resection and anastomosis of a segment of the pelvic urethra in male dogs, the urethral diameter was better maintained when an indwelling urinary catheter was kept in place for 2 weeks postoperatively, rather than when intermittent catheterization was performed as needed for signs of dysuria.12
Resection/anastomosis of the urethral stricture was not considered a reasonable option for the dog described herein because of the risk of further nerve and vascular compromise from the amount of dissection that would have been required to mobilize healthy urethra and the likely inadequate urethral length that would remain after stricture resection. Because of the proximal location of the stricture, prepubic or subpubic urethrostomies were also not viable options. An onlay SIS graft was chosen because of its ability to induce regeneration of native tissue without scarring. Small intestinal submucosa provides structural proteins, growth factors, cytokines, and their inhibitors in physiological proportions and native three-dimensional ultrastructure.16 Host cells interact with this extracellular matrix bioscaffold, eventually replacing it with site-specific tissue that is responsive to local mechanical and environmental stresses.17 The SIS also appears to have antibacterial properties, which have been attributed to certain peptides released from the SIS (as it is broken down by host cells) and to the rapid capillary ingrowth induced by SIS.18,19
Dogs that received bladder augmentation with SIS after partial experimental cystectomy regained normal bladder capacity, contractile function, afferent innervation, and regenerated mucosal, muscular, and serosal layers.20,21 Replacement of the SIS by host tissue progressed from the periphery toward the center of the graft and was complete in 3 to 4 weeks.22 Repair of rabbit urethral defects with onlay grafts of SIS led to regeneration of normal urethral epithelium with a vascularized collagen matrix and circular bundles of smooth muscle.23,24 Strictures of the bulbar and penile urethra in humans have been successfully resolved with onlay grafts of SIS.2,25 An intact urethral wall and patent urethral lumen were achieved after SIS augmentation urethroplasty and subsequent balloon dilatation in the dog of this report. No clinical evidence of urine leakage from the urethral repair site was seen postoperatively, although with the indwelling urinary catheter, the ability of the SIS graft to create a waterproof seal was not truly tested.
In humans, 2 to 3 weeks of internal stenting is recommended to allow adequate time for epithelialization after placing an onlay SIS urethral graft.2 In the dog described in this case, an indwelling urethral catheter was maintained for 2 weeks following the SIS urethroplasty. A closed system with the collecting bag positioned below the level of the penile urethra (to avoid reflux) was used to decrease the risk of infection. The dog remained hospitalized during the period of catheterization so the catheter could be closely managed, as recommended by Drinka (2006).26 The urethral diameter was assessed with contrast urethrograms at 8 and 14 days after placement of the SIS. No significant change in luminal diameter was seen between these two time points, so the urethral catheter was removed on day 14. A cystostomy tube was placed at this time because of concerns that the neurological damage suffered by the bladder would render it unable to empty adequately, especially in the face of urethral narrowing.
Restricture did occur at the SIS site in this dog. Potential causes of restricture after SIS implantation include failure of epithelialization and neovascularization, a poorly vascularized recipient bed, infection, and hematoma.2 Additional contributors to restricture in this dog may have been continued organization of the fibrous tissue surrounding the bladder and urethra (suggested by the circumferential hypoechoic tissue seen on ultrasound) and consumption of the SIS by an ongoing inflammatory process. Collapse of the SIS toward the lumen seems unlikely, because the urinary catheter was maintained for 2 weeks as a stent, and the urethral lumen following dilatation was narrower from left to right than from dorsal to ventral. In 50 men with bulbar and penile urethral strictures repaired with onlay grafts of SIS, the recurrence rate of strictures was 20%, and all strictures were resolved with subsequent balloon dilatation or surgical revision.2 Approximately 180° of the urethra was replaced with SIS in this dog. While the maximum size of urethral defect that can be successfully replaced has not been determined, SIS has been reported to be unsuccessful as a replacement for the entire circumference of small tubular structures such as ureters and bile ducts because of collapse of the tube and lack of peristalsis during healing.17,27
Balloon dilatation has been reported as a safe and effective treatment for urethral strictures in humans.4 The distended balloon applies a radial force that stretches the urethral wall, counteracting contraction of the incised mucosal edges and possibly increasing blood flow around the urethral incision.4 The increased oxygenation associated with improved blood flow has been hypothesized to decrease the levels of profibrotic cytokines such as transforming growth factor-beta.28 In humans, balloon dilatation is less painful and causes less urethral bleeding than sequential rigid dilatation or internal urethrotomy; it is equally effective as internal urethrotomy in resolving the stricture; and it can be performed under local anesthesia.4,29 General anesthesia is typically required in animals.
In the dog described in this report, insertion of the balloon catheter over a guidewire was key to accessing the strictured area of the urethra. The selected guidewire was only 0.035 inches in diameter, had a steerable angle tip, and was hydrophilic. These properties made it very smooth when in contact with fluid and allowed the wire to be passed easily through small areas, such as the strictured urethra.
Two challenges are generally faced when performing balloon dilatation. First, the balloon can become displaced distal or proximal to the stricture during dilatation. Mixing contrast agent with saline to distend the balloon helps in visualizing its placement relative to the stricture under fluoroscopic guidance, and distending the balloon slowly helps keep it in place at the stricture site. Contrast is not used alone, as its viscosity makes inflation and deflation of the balloon more difficult. Second, once deployed even partially, the balloon does not return to its original size. Because the balloon was not ideally positioned within the stricture during the first dilatation, it was deflated and attempts were made to center it more accurately; however, the deflated balloon was too large to fit in the stricture. This experience illustrated the importance of ensuring the catheter is pulled distally, especially in cases where the balloon must be deflated midprocedure. If the catheter moves cranially, the deflated balloon may not fit back through the stricture, necessitating a cystotomy for transection and removal of the catheter. Unfortunately, a balloon inflation device, which provides a measured inflation force, was not available. An inflation device allows more precise and quantifiable balloon inflation, prevents balloon overinflation and rupture, and provides significantly higher pressures within the balloon than can be achieved with a handheld syringe (as was used in our case). Had an inflation device been used, the balloon could have been deflated more completely. In addition, the stricture possibly may have been effaced during the initial dilation procedure. Centering of the balloon within the stricture site became easier, and the duration of the dilation procedure decreased as the operators gained experience.
In the human literature, timing and duration vary for balloon dilatation of urethral strictures. The incidence of restricture after internal urethrotomy in humans decreased from 55.6% to 10.5%, with regularly scheduled postoperative balloon dilatations performed weekly for 1 month, at 3 and 6 months postsurgically, and then once yearly.28 This schedule would be challenging to maintain in many animals because of the need for general anesthesia, cost constraints, and (ideally) the need for access to fluoroscopy (although this procedure could be performed with digital radiography and likely standard radiography, if necessary). In the dog of this report, it was unknown how soon balloon dilatation could be safely attempted after SIS urethoplasty. The majority of implanted, single-laminate SIS is replaced by host tissue within 30 days,17 so it is unlikely that the SIS was still present when dilatation was performed 3 months postSIS implantation. In retrospect, earlier dilation attempts may have been beneficial in this dog.
Only three reports of balloon dilatation of canine urethral strictures were found in the veterinary literature. In one report, a male Scottish terrier with a urethral stricture secondary to catheter-induced trauma was responsive to three 5-minute balloon dilatations performed sequentially under the same anesthetic episode.6 It is not clear if full balloon dilatation was achieved on the first attempt. The dog was followed for 18 months and had no recurrence of clinical signs. In the second report, a female Dalmatian with granulomatous urethritis improved for approximately 8 months after a single 2-minute balloon dilatation of a urethral stricture.7 Finally, in a case series of dogs and cats with urethral ruptures, one neutered male dog with a prostatic abscess and urethral tear from traumatic catheterization developed a urethral stricture 5 weeks after prostatic omentalization and urinary diversion with a urethral catheter.5 The stricture was successfully dilated with a balloon catheter. Details of the dilation procedure and duration of follow-up were not provided in any of the above-mentioned reports. Further, the use of a balloon inflation device was not reported in any of the aforementioned cases.
The dog in the current study required three separate procedures before dilatation was achieved. The urethral diameter increased acutely and dramatically on the third attempt. Balloon dilatations that do not efface the stricture are not likely to be effective, and a stronger balloon or increased inflation pressures should be attempted as long as the balloon’s rated burst pressures are not exceeded. Without an inflation device to measure the pressure delivered, the person performing the inflation is left to use his or her best judgment in not exceeding balloon burst pressure. Experimental inflation of a balloon catheter using different degrees of hand pressure prior to the actual procedure may be helpful. In the case described here, the same operator performed the procedure each time, injecting the same amount of fluid into the balloon and maintaining balloon distension for the same period of time. Considerable pressure was required each time to keep the fluid in the balloon, suggesting the stricture site was fibrotic or scarred.
If multiple balloon dilatations had been performed in the first session, urethral distension may or may not have been achieved. Additional balloon dilatations in the first session would have required the use of a new catheter because of the inability to reposition the deflated balloon of the original catheter in the stricture. The concern at the time was that cumulative inflammation caused by repeated pressure on the urethral wall would have increased the risk of restricture. Even in the healthy urethra, balloon distension is not totally benign; submucosal urethral hemorrhage and a mild reversible inflammatory reaction were reportedly present 1 day after experimental 15-minute balloon distension in the distal canine urethra.30 Waiting 3 days between dilation attempts in the dog of this report gave an opportunity for any inflammation to subside. Inflammation was further addressed with carprofen administration. The cystostomy tube was used for urine diversion during this time to decrease the risk of urine-induced inflammation of submucosa exposed by mechanical and/or ischemic mucosal damage incurred during the dilation process.30
Luminal narrowing of ≥60% appears to be necessary before dogs show clinical evidence of urethral stricture.12 Positive-contrast urethrography underestimates the amount of stricture present relative to what is found on postmortem anatomical assessments.12 Thus, regardless of the radiographic image, the clinical presentation of the animal is ultimately the most important factor in determining the management plan for urethral strictures. Despite radiographic evidence of persistent urethral narrowing in the dog of this report, he was able (as reported at the time of the final examination) to intermittently produce a moderate urine stream, and the bladder was relatively easy to manually express. The majority of the dog’s persistent urinary difficulties were suspected to be neurological rather than anatomical in nature. It is hypothesized that urodynamic studies would be needed to better establish the cause of the persistent issues. Urethral stenting is an additional option for this dog if the clinical improvement achieved with the balloon dilatations described in this report ultimately prove transient.31
Urinary incontinence may manifest as leakage of urine during the storage phase of micturition and/or the inability to control urinary excretory function. Both of these manifestations were present in the dog of this report.31 Several possible explanations are possible for this dog’s persistent urinary incontinence following SIS urethroplasty and balloon dilatation. First, damage to the nerves of micturition may have occurred during blind palpation for a retained testicle and exteriorization of the prostate at the time of the initial surgery. Second, the caustic action of extravasated urine may have further compromised nerves already damaged during inadvertent prostatectomy. Third, a single episode of bladder overdistension for as little as 1 hour can lead to acute, long-lasting detrusor decompensation resulting from (at least in part) axonal degeneration caused by vascular compromise in the bladder wall.32,33 Detrusor atony in this dog could be secondary to the day of bladder outflow obstruction after the initial surgery and/or the following 4 weeks of intermittent, partial urinary bladder decompression. Because the dog is able to intermittently produce a moderate stream, complete detrusor atony seems unlikely.
Conclusion
Urinary incontinence and urethral stricture are potential complications of inadvertent prostatectomy during cryptorchidectomy or other processes resulting in circumferential urethral lesions and/or cystourethral anastomosis in the dog. Protection of the urethral surgical site from contact with urine is important during the healing process. Restricture is a possible sequela of SIS augmentation urethroplasty. Balloon dilatation can successfully resolve clinical signs of urethral stricture after SIS onlay graft repair. Multiple balloon dilatations may be required before luminal distension is achieved.
Amoxicillin-clavulanic acid; source unknown
Phenylpropanolamine; source unknown
Oxilan 300; Guerbet LLC, Bloomington, IN 47403
Ampicillin; Abraxis Pharmaceutical Products, Schaumburg, IL 60173
Vet BioSISt; Global Veterinary Products, Inc., New Buffalo, MI 49117
Polydioxanone; Ethicon, Inc., Somerville, NJ 08876
Doxycycline; Ivax Pharmaceuticals, Inc., Miami, FL 33137
Drainage catheter with locking loop; Infiniti Medical, LLC, Haverford, PA 19041
Dibenzyline; Wellspring Pharmaceutical Corporation, Bradenton, FL 34202
Weasel wire; Infiniti Medical, LLC, Haverford, PA 19041
French Marauder PTA Catheter #617103; B. Braun Medical, Inc., Bethlehem, PA 18018
Rimadyl; Pfizer Animal Health, Exton, PA 19341
Bethanechol; Barr Laboratories, Inc., Pomona, NY 10970
Citation: Journal of the American Animal Hospital Association 46, 5; 10.5326/0460358
Citation: Journal of the American Animal Hospital Association 46, 5; 10.5326/0460358
Citation: Journal of the American Animal Hospital Association 46, 5; 10.5326/0460358
Citation: Journal of the American Animal Hospital Association 46, 5; 10.5326/0460358
Urethrocystograms performed under general anesthesia in a 10-month old, male German shepherd. (A) Four weeks after cystourethral anastomosis subsequent to inadvertent prostatectomy during cryptorchidectomy and 2 days prior to urethral augmentation with small intestinal submucosa (SIS), a focal stricture (arrow) is present in the proximal urethra. Mild dilatation of the pelvic urethra distal to the stricture is present. (B) Eight days after SIS augmentation, urethral narrowing is present at the previous site (thin arrow). Caudal to this stricture is a focal area of urethral dilatation followed by a second area of narrowing (thick arrow). (C) Fourteen days after SIS augmentation, stricture persists at the original site (arrow), while the caudal area of narrowing is filled with more contrast than on day 8. (D) Minimal contrast passed through the stricture (arrow), even after injection with a Foley catheter balloon inflated in the pelvic urethra or after placement of contrast in the bladder via the cystostomy tube (not shown) and manual bladder expression.
Intraoperative photograph of the bladder and proximal urethra during augmentation urethroplasty. The dog is in dorsal recumbency, and cranial is to the left of the photograph. A marked amount of tissue reaction is evident in the caudal abdominal cavity and abdominal wall. Multiple adhesions were resected prior to this photograph. An onlay graft of SIS (outlined by arrows) has been sutured to the ventral aspect of the urethrotomy and cystotomy incisions.
Fluoroscopic images of the third attempt at balloon dilatation of the proximal urethral stricture. (A) A 5.8-French balloon dilation catheter is distended with a 50:50 mixture of saline and contrast material at the start of a third attempt to expand the urethral stricture. The center of the balloon is compressed by the stricture (arrow), while both ends of the balloon are fully expanded. Small, round, radiopaque markers—spaced 3 cm apart—are seen at either end of the balloon. (B) After approximately 2 minutes of expansion, the strictured area of the urethra acutely expanded, allowing the center of the balloon to maximally distend.
Fluoroscopic image of a urethrocystogram performed 13 months after successful balloon dilatation of the proximal urethral stricture. The diameter of the urethra at the previous stricture site (arrow) in the proximal urethra is unchanged from images taken 10 days after the successful balloon dilatation.
Contributor Notes
