Use of tubularized peritoneal free grafts as urethral substitutes in the rabbit

Buccal mucosal graft urethroplasty in male cats with traumatic complete urethral rupture

OBJECTIVE

To evaluate the feasibility of buccal mucosal graft urethroplasty for repairing complete urethral rupture in cats.

ANIMALS

15 male domestic shorthair cats with traumatic complete urethral rupture.

PROCEDURES

In each cat, a section of buccal mucosa was harvested, sutured, and formed into a tubule by use of an 8F indwelling catheter as support. This tubular graft was connected to both ruptured ends of the urethra to renew the urinary passage. The catheter was left in place until the absence of leakage was confirmed by positive contrast retrograde urethrography. After spontaneous urination was confirmed, cats were discharged from the hospital. Six months later, urethrography was repeated and owners were asked to score their cats' urinary function and quality of life.

RESULTS

13 cats recovered well following surgery, with no complications in the oral cavity or surgical site and no signs of difficulty or discomfort when urinating. Urethrography 2 weeks and 6 months after surgery revealed no stricture or leakage in the abdominal cavity. The 2 remaining cats developed a urethral stricture and underwent second surgery with a successful outcome. At the 6-month follow-up, 14 cats had only mild urinary signs, and 1 cat had incontinency. Owners indicated they were delighted (n = 14) or pleased (1) with their cats' quality of life.

CLINICAL RELEVANCE

Buccal mucosa was found to be a good source of graft tissue for performance of urethroplasty in male cats, yielding satisfactory outcomes with few postoperative complications. The described technique may be suitable for severe and complicated cases of urethral rupture in male cats.

Tissue-engineered autologous peritoneal grafts for bladder reconstruction in a porcine model

Ileal neobladder construction is a common treatment for patients with bladder cancer after radical cystectomy. However, metabolic disorders caused by transposed bowel segments occur frequently. Bladder tissue engineering is a promising alternative approach. Although numerous studies have reported bladder reconstruction using acellular and cellular scaffolds, there are also disadvantages associated with these methods, such as immunogenicity of synthetic grafts and incompatible mechanical properties of the biomaterials. Here, we engineered an autologous peritoneal graft consisting of a peritoneal sheet and the seromuscular layer from the ileum. Three months after the surgery, compared with the neobladder made from the ileum, the reconstructed neobladder using our new method showed normal function and better gross morphological characteristics. Moreover, histopathological and transcriptomic analysis revealed urothelium-like cells expressing urothelial biomarkers appeared in the neobladder, while no such changes were observed in the control group. Overall, our study provides a new strategy for bladder tissue engineering and informs a variety of future research prospects.

Evaluation of crural release and ischial osteotomy for relief of tension in the repair of large segmental urethral defects in male cats

OBJECTIVE

To examine if the tension at the site of a urethral anastomosis can be relieved by performing either a crural release technique or an ischial osteotomy technique.

STUDY DESIGN

Cadaveric study and 2 case reports.

ANIMALS

Adult male cat cadavers (n = 18).

METHODS

Cats were divided into 2 groups; crural release (n = 9) and ischial osteotomy (n = 9). In each group, 20%, 25%, and 30% of the pelvic urethra was excised in 3 cats. The length of the urethral defect was measured after excision of the urethral segment, and after approximation, before and subsequent to the tension relieving technique performed. Two clinical cases are described.

RESULTS

Both crural release and ischial osteotomy were effective in relieving the tension encountered at the urethral anastomosis after removal of 20% of the urethral length. In the ischial osteotomy group, apposition without tension after removing up to 30% of the intrapelvic urethral length was easily achieved. A similar technique was successfully used in 2 clinical cases.

CONCLUSION

Crural release and ischial osteotomy techniques allow approximation and tension free anastomosis of large segmental defects of the pelvic urethra in cats.

Tubularized urethral replacement using tissue-engineered peritoneum-like tissue in a rabbit model

INTRODUCTION

This study aims to investigate whether mesothelial cells could function as seed cells to construct tissue-engineered peritoneum-like tissue for urethral reconstruction in a rabbit model.

MATERIALS AND METHODS

Bladder acellular matrices were prepared and trimmed to 1.5 × 1 cm. Nine male rabbits underwent omentum biopsy and autologous mesothelial cells were isolated. After in vitro expansion, the cells were seeded onto the matrices and incubated for 7 days. In 18 rabbits, a pendulous urethral segment 1.5 cm long was totally excised and urethroplasty was performed with tubularized matrices seeded with cells in 9 animals and without cells in 9 as controls. Urethrography was performed at 1, 2 and 6 months postoperatively. Meanwhile, the neourethras were harvested and analyzed grossly and histologically.

RESULTS

Histological analysis of the cell-seeded grafts revealed a loose collagen matrix covered with a single layer of mesothelim. Serial urethrography indicated a wide urethral caliber without stricture formation in animals implanted with cell-seeded matrices, while all animals of the control group developed stricture. Histological analysis of the implanted cell-seeded matrices demonstrated a normal urethral architecture by 1 month, composed of multilayers of urothelium surrounded by smooth muscle bundles, which became increasingly organized with time. By 6 months, the neourethra could be hardly distinguished from native urethra both grossly and histologically.

CONCLUSIONS

Autologous mesothelial cells could be successfully used as seed cells for tubularized urethral reconstruction in male rabbits.

Tissue engineering of the penis

Congenital disorders, cancer, trauma, or other conditions of the genitourinary tract can lead to significant organ damage or loss of function, necessitating eventual reconstruction or replacement of the damaged structures. However, current reconstructive techniques are limited by issues of tissue availability and compatibility. Physicians and scientists have begun to explore tissue engineering and regenerative medicine strategies for repair and reconstruction of the genitourinary tract. Tissue engineering allows the development of biological substitutes which could potentially restore normal function. Tissue engineering efforts designed to treat or replace most organs are currently being undertaken. Most of these efforts have occurred within the past decade. However, before these engineering techniques can be applied to humans, further studies are needed to ensure the safety and efficacy of these new materials. Recent progress suggests that engineered urologic tissues and cell therapy may soon have clinical applicability.

Use of free peritoneal and bladder mucosal grafts as ureteral mucosa substitutes for management of avulsion of the ureteral mucosa in a dog model

BACKGROUND AND PURPOSE

Avulsion of the ureteral mucosa is one of the most serious complications of ureteroscopy and considered challenging for urologic surgeons. In this study, we developed two novel methods to reconstruct the impaired ureter.

MATERIALS AND METHODS

After ureteral mucosal avulsion in a canine model, ureteral reconstruction was performed in one of three ways: free tabularized peritoneal grafts (group A, n = 6); bladder mucosal grafts (group B, n = 6); or simple stenting technique (control group [n = 3]). At postoperative week 10, evaluation with intravenous urography (IVU) was followed by harvesting of reconstructed ureter segments for pathologic analysis.

RESULTS

IVU showed nonvisualization of the collecting system of the affected side and histologic evaluation showed imperforation or stenosis in all animals in the control group. IVU showed good visualization of the reconstructed ureter without stenosis in group A and in most animals in group B. There was a mild dilation but no obvious stenosis in one animal in group B. Microscopically, all the reconstructed ureteral lumens were uniformly lined with transitional epithelium. Extensive neovascularity was evident in the subepithelial layer with a streaming of fibroblasts toward the neomucosa.

CONCLUSION

Replacing the avulsed mucosa in the injured ureter with tubularized peritoneal free grafts or bladder mucosal grafts may be an optimal method to manage avulsion of the ureteral mucosa.

Reconstruction of the urethral defects with autologous fascial tube graft in a rabbit model

AIM

To investigate the feasibility of the autologous fascia graft in urethra defect reconstruction.

METHODS

In 24 adult male rabbits, a standardized defect (17 mm) was created within the midportion of each urethra. Two-cm long fascial tube grafts were interposed between the cut ends of the urethra. Twenty-four rabbits were divided into 12 groups. At 0, 3, 10, 15, 21, 30, 45, 60, 90, 120, 150, and 180 days postoperatively, one group was killed. In the first four groups, rabbits were killed and specimens were obtained for histological examination. After 21 postoperative days, in the subsequent eight groups, retrograde urethrograms were carried out to evaluate urethral patency and caliber, then rabbits were killed and specimens were obtained.

RESULTS

In the histological study, advancement of the urethral transitional epithelium along scaffold provided by the fascial graft was determined. At the 30th day, the new urethra was completely covered with the transitional epithelium. Fistula formation was observed in two of 24 rabbits. In urethrograms, narrowing was determined in three of 16 rabbits.

CONCLUSION

For segmental urethral reconstruction, fascial graft is a good urethral substitute because of its rapid epithelization capacity, low contraction degree and thinness. We therefore propose the use of fascial grafts for reconstruction of male-urethra defects in humans.

Repair of Urethral Defects Using Fascia Lata Autografts in Dogs

OBJECTIVE

To evaluate the feasibility of urethroplasty using a free fascia lata (FL) graft in the dog.

STUDY DESIGN

In vivo experimental study.

ANIMALS

Mixed-breed dogs (n=14).

METHODS

Half of the circumference of the urethra, approximately 1.5 cm long, was excised in 14 male dogs to induce a urethral defect. FL (approximately 2 cm x 2 cm) harvested from the lateral thigh was sutured to the urethra using a 3-0 polyglactin 910 continuous pattern. Dogs were monitored daily for bladder distention and had urethral catheters until normal voiding was observed. On day 60, each dog had a positive contrast urethrogram, and then 8 dogs were euthanatized for gross and histologic examination. Six dogs were monitored for urologic problems for 6 months, and a positive contrast urethrogram was repeated.

RESULTS

All dogs recovered successfully; 4 dogs had difficulty voiding for 2-3 days and urine was aspirated from these dogs every 3 hours until signs of painful urination disappeared. On positive contrast urethrograms, urethral anatomy was considered normal except in 4 dogs that had an irregular contour. Gross urethral examination confirmed an absence of ulceration, stricture, diverticula, or fistula formation, and the FL-lined graft survived in all dogs. No degenerative and reparative responses were observed. On histologic examination of the penile urethra, the lumen was intact, covered with transitional epithelium, and surrounded by corpus spongiosum with cavernous spaces and blood-filled vessels.

CONCLUSIONS

Free FL grafts are incorporated satisfactorily and would appear to be useful for repairing urethral defects.

CLINICAL RELEVANCE

FL grafts should be considered for repair of urethral defects in dogs.

Urethroplasty using a bovine pericardium graft: an experimental study using normal urethras from dogs

The use of bovine pericardium as a urethral patch to substitute a ventral segment of canine urethras was studied. Healing, epithelial growth, urethral permeability, fistulas, and calcification were analyzed. Thirty male mongrel dogs of medium and large size underwent resection of a ventral segment of the medial urethra measuring 2.0 x 0.5 cm, which was replaced with a bovine pericardium graft, treated with buffered glutaraldehyde and preserved in formaldehyde. Two running sutures of polygalactin 5-0 were applied, one on each side of the patch. The corpus spongiosum was closed with uninterrupted suture and the skin with interrupted suture of polygalactin 5-0. Six months later, the animals were examined and sacrificed under anesthesia. Retrograde urethrograms showed that the urethral healing was complete in six of the 30 animals, without stenosis, fistulas or dilations. Microscopic examination showed complete epithelization of these six urethras. The remaining 24 animals presented urethrocutaneous fistulas without stenosis, demonstrated by urethral catheterism using a 10-Fr plastic catheter. These data show that a successful urethral reconstruction of the penile urethra was possible in only 20% of the operated animals. Infection and leakage may be the cause of the urethrocutaneous fistulas present in 80% of cases. Further studies are necessary to determine whether such fistulas are avoidable. If they are, the bovine pericardium may well be an option in the treatment of urethral lesions in dogs.

Patch Urethroplasty Using a Fascia lata Autograft in Male Rabbits

INTRODUCTION

Urethral reconstruction is difficult when the genital skin is not available for surgery. We evaluate the feasibility of using the autologous fascia lata as a graft for urethral repair.

MATERIALS AND METHODS

10 male rabbits underwent urethroplasty after creation of a ventral urethral defect. The defect was repaired using a graft harvested from the fascia lata. The animals were divided into three groups and sacrificed at 2, 4 and 12 weeks postoperatively. Radiologic control was performed after 10-12 days and before sacrifice.

RESULTS

In the 10 rabbits subjected to surgery, no case of death or wound infection was observed. During urethrography, a fistula was observed in 2 animals. In the remainder (n = 8), histological analysis showed the preservation of the original laminar structure without graft shrinkage or fibrosis. On the luminal side of the patch, a new line of urothelium appeared in the 2nd week after surgery. After 3 months, the new epithelium was multilayered and the graft edges were not detectable. No voiding dysfunction was detectable in 8 rabbits.

CONCLUSIONS

Our study suggests the feasibility of using the autologous fascia lata for urethral patch repair.

Treatment of urethral defects: skin, buccal or bladder mucosa, tube or patch? An experimental study in dogs

PURPOSE

We studied 3 graft materials and 2 urethroplasty techniques in 24 adult male mongrel dogs.

MATERIALS AND METHODS

The animals were divided into 2 equal groups. In group 1 a 4 cm. segment of perineal urethra was excised and tubed urethroplasty was performed using free full-thickness skin, buccal and bladder mucosa grafts in 4 dogs each. In group 2 a 4 cm. urethral strip was excised and onlay urethroplasty was performed using the same graft materials in 4 dogs each. Retrograde urethrography was done and the animals were sacrificed at week 12. Autopsy specimens were calibrated with a 10Fr catheter. Hematoxylin and eosin stained sections were examined. Masson's trichrome stain was used to determine the extent of fibrosis.

RESULTS

Urethral stricture was diagnosed by radiology and confirmed by calibration in 8 of the 12 dogs (66%) in group 1 but in only 1 of the 12 (8%) in group 2 (p <0.004). Buccal mucosa grafts were associated with the lowest stricture rate of 12%, followed by 37% for bladder mucosa and 62% for skin (p <0.2). There was no difference in neovascularization among the 3 grafts. Graft shrinkage was less than 10% for buccal mucosa compared with 20% to 40% for skin and bladder mucosa. The shrinkage rate was similar for the onlay and tube techniques. The intensity of chronic inflammation and fibrosis was highest in the skin grafts. Circumferential fibrosis was noted in association with tubed urethroplasty but not with the onlay technique.

CONCLUSIONS

The theoretical advantages of buccal mucosal grafts were pathologically demonstrated. When possible, grafts should be used as an onlay rather than as a complete tube.

Free peritoneal grafts for patch urethroplasty in male rabbits

PURPOSE

We evaluated the feasibility of urethroplasty using a free peritoneal graft in a rabbit model.

MATERIALS AND METHODS

In 12 male rabbits a urethral defect was created by excising a 3 x 5 mm. portion of the ventral urethral surface. The defect was immediately repaired with a free peritoneal graft harvested via a left flank incision.

RESULTS

There were 2 intraoperative deaths and 1 death on day 8 postoperatively. These animals were excluded from study. The remaining 1, 4 and 4 rabbits were sacrificed 3, 5 and 9 weeks after surgery, respectively. Macroscopic examination of the urethra revealed no stenosis or diverticula, while a fistula was present in 3 of the 9 animals. Histological study of the fistulous tracts showed chronic granulomatous inflammation. In the remaining 6 rabbits there was graft adherence. The inner surface of the graft was uniformly lined with normal urothelium, while in some cases acute inflammatory cells were present in the subepithelial layer.

CONCLUSIONS

Our experience indicates that the ease of harvesting free peritoneal grafts and their satisfactory adherence to the urethra makes them a valid alternative for repairing urethral defects.

Tunica vaginalis onlay urethroplasty as a salvage repair

PURPOSE

We review our experience with tunica vaginalis onlay urethroplasty for urethral repair after multiple previous hypospadias repairs.

MATERIALS AND METHODS

From January 1992 through December 1997 we repaired the urethra in 10 boys and 1 man using a tunica vaginalis onlay flap. The tunica vaginalis was placed as a patch on the urethra that was proximal to the glans or brought out to the urethral meatus.

RESULTS

No intraoperative complications or difficulties were associated with harvesting the tunica vaginalis. Of the 4 children and 1 adult in whom the onlay flap was brought out to the urethral meatus meatal stenosis developed in 3 (60%), while 2 void without problems. In 6 children the onlay flap was placed proximal to the glans and in 1 who was lost to followup 2 discontinuous patches were placed. In 3 of the 5 remaining boys (60%) stricture developed, while 2 void without problems.

CONCLUSIONS

Tunica vaginalis onlay urethroplasty results in a substantial complication rate. We did not confirm any advantage of its use.

Tunica vaginalis onlay urethroplasty as a salvage repair

PURPOSE

We review our experience with tunica vaginalis onlay urethroplasty for urethral repair after multiple previous hypospadias repairs.

MATERIALS AND METHODS

From January 1992 through December 1997 we repaired the urethra in 10 boys and 1 man using a tunica vaginalis onlay flap. The tunica vaginalis was placed as a patch on the urethra that was proximal to the glans or brought out to the urethral meatus.

RESULTS

No intraoperative complications or difficulties were associated with harvesting the tunica vaginalis. Of the 4 children and 1 adult in whom the onlay flap was brought out to the urethral meatus meatal stenosis developed in 3 (60%), while 2 void without problems. In 6 children the onlay flap was placed proximal to the glans and in 1 who was lost to followup 2 discontinuous patches were placed. In 3 of the 5 remaining boys (60%) stricture developed, while 2 void without problems.

CONCLUSIONS

Tunica vaginalis onlay urethroplasty results in a substantial complication rate. We did not confirm any advantage of its use.