Ureteral Replacement Research Articles

ELASTIN CONDUIT FOR URETERAL REPLACEMENT IN A PORCINE MODEL

We investigated the feasibility and biocompatibility of a homologous elastin base conduit as a ureteral substitute in the porcine model. In 13 female domestic swine, a 2.5 to 3-cm mid-segment of unilateral ureter was resected and replaced with the elastin conduit. At varying intervals (from 1 to 12 weeks), the animals were euthanized and the specimens were prepared for histologic evaluations. Twelve of 13 animals entered the end point in this study. One pig died peri-operatively due to anesthesia complication. The histologic study showed that the transitional epithelia cells completely lined the surface of the elastin conduit lumen at 4 weeks, and a progressive neovascularization infiltrated through elastin matrix. However, at 12 weeks after implantation, there was no evidence of smooth muscle cells regeneration. We also noticed the presence of submucosa hyperplasia and localized ossification on the grafts. The elastin conduit allows transitional urothelia cells regeneration without incrustation. It can be modified as a potential ureteral replacement.

Ureteral Segment Replacement Using a Circumferential Small-Intestinal Submucosa Xenogenic Graft

ABSTRACT We wished to determine whether small-intestinal submucosa (SIS) will epithelialize when used as a ureteral replacement material. An 11-mm segment of native ureter was excised from eight New Zealand White rabbits and replaced with an 11-mm porcine SIS graft, which was circumferentially wrapped around a ureteral stent. The SIS ureteral grafts were harvested at 11 days or 35 days postimplantation and examined grossly and by standard light microscopy techniques. Partial epithelialization with the ingrowth of urothelium, smooth muscle cells, and blood vessels was observed in the grafts harvested at 11 days postimplantation. The SIS ureteral grafts examined at 35 days postimplantation showed additional restructuring of the smooth muscle cell layer and more organized epithelialization in comparison to the SIS graft examined at 11 days. After 35 days of regenerative healing, elements of all three layers of the native ureter were observed within the collagen matrix of the SIS graft. No significant complications were observed, but all subjects (8/8) demonstrated mild intra-abdominal adhesions. Mild collecting system dilatations were observed in 4/4 (100%) of the animals harvested at 35 days and in 0/4 (0%) of the animals harvested at 11 days. We have this demonstrated in this preliminary study that SIS xenografts will epithelialize when used as a ureteral replacement material. The repair mechanism of these ureteral grafts occurred through a regenerative healing process rather than by scar formation. With further studies, this material may prove to be a useful treatment option in patients with ureteral injuries.

THE APPENDIX AS RIGHT URETERAL SUBSTITUTE IN CHILDREN

The appendix has occasionally been used to replace sections of the right ureter. We reviewed the literature of the last 25 years on the use of the appendix as right ureteral replacement and report our experience with right ureteral substitution using the appendix. We retrospectively reviewed the charts of 3 children who underwent appendiceal replacement of the right ureter. The appendix replaced the upper third of the ureter and the lower ureter in 1 and 2 cases, respectively. Followups of 4, 7 and 15 years, respectively, demonstrated that the appendix transports urine satisfactorily and permits renal function to be maintained with no evidence of obstruction. We believe that our small series supports the use of the appendix as a right ureteral substitute in select cases.

Use of reconstructed small intestine submucosa for urinary tract replacement.

We used reconstructed SIS (ReSIS), a photocrosslinked biomaterial, to create grafts in various shapes and sizes. Sheets of ReSIS were placed in 14 swine to repair bladder defects, and ReSIS tubes were placed in six swine to replace a segment of excised ureter. Histologic analysis of the bladder repair revealed transitional urothelial cells lining the ReSIS by 1 week. After 2 weeks, fibroblasts and mononuclear cells had infiltrated the ReSIS, neovascularization had occurred, and the urothelial lining was more complex, containing multiple cell layers. After 4 weeks, a definite submucosa was present and the ReSIS was starting to degrade. An initial muscular regeneration was demonstrated at 12 weeks. No foreign body reaction, calcification, or sedimentation was noted in any animal. The ureteral implants showed identical histologic changes, without obstruction or leakage of the replaced segment. The ReSIS allowed rapid urothelial regeneration, ingrowth of new blood vessels, and the orderly deposition and organization of new collagen. Our study demonstrates that the photocrosslinking technique used to create larger sheets and tubes of this biomaterial (ReSIS) does not detract from the positive attributes of the SIS and should improve its usefulness in accomplishing larger bladder augmentations and ureter replacements.

LAPAROSCOPIC ILEAL URETER

We describe the operative technique of laparoscopic ileal ureter replacement. A transperitoneal 3-port approach was used. Ileovesical and pyeloileal anastomoses were performed with intracorporeal laparoscopic freehand suturing and knot tying techniques. Operating time was 8 hours and blood loss was 200 cc. Both anastomoses were immediately watertight. Hospital stay was 4 days and a cystogram at 14 days confirmed widely patent anastomoses without extravasation. Laparoscopic ileal ureter replacement satisfactorily duplicates established open surgical principles. The laparoscopic technique is efficient and technically straightforward.

The prosthetic ureter.

Ureteral replacement has always been a challenge. Two approaches have been explored: in situ augmentation or replacement and extra-anatomic passage of a conduit. An in-situ prosthetic ureter is basically a simple al. loplastic tube connected to the urinary tract by end-to-end sutures or by intubation and closure. Antireflux devices and peristaltic mechanisms are not necessary. Among the in-situ designs, only those composed of silicone and silicone rubber have performed at all well. Tissue engineering and acellular matrix grafts have produced impressive early results. Subcutaneous ureteral replacement with alloplasts, including a coaxial assembly of an inner silicone and outer expanded polytetrafluoroethylene tube, has produced good results. In the future, we are likely to see bioengineered neotissue combined with highly porous and infection-resistant alloplasts to create better and more functional neo-organs.

Le remplacement prothétique des uretères

Study aim The aim of this study is to demonstrate the reliability of silicone prosthesis for the replacement of ureters. This prosthesis derives from the biliary prosthesis developed after a personal experimental study continued by Triboulet. Patients and methods In 38 patients suffering from a malignant disease, a right silicone prosthesis was used for the replacement of an ureter during a 20-year period. There were 30 female and eight male patients. The mean age was 71 (range: 51–88 years). Forty one prostheses were used; one patient underwent two successive operations on the same side with a change of prosthesis, and two patients required a bilateral prosthesis. There were 12 gynaecological carcinomas (three with ureteral fistula), three prostatic carcinomas, 16 cancers of the rectum and recto-sigmoid junction, four cancers of the right colon with retroperitoneal carcinomatosis, and three ureteral fistulas after extended colonic resection. Results Early complications were limited to ureteral fistulas ( n = 6, 16%) in patients who had already a preoperative fistula ( n = 3) and in patients with peritoneal metastases on the superior wall of the bladder. The secondary destruction of the kidney (four secondary nephrectomies) occurred when the function of the kidney was already impaired at the time of the procedure. There were no secondary fistulas, no secondary obstruction of the prosthesis. The longest follow-up was 69 months. Conclusion The silicone prostheses used for the replacement of ureters are reliable and still permeable beyond 5 years. The protection of the renal function in patients often submitted to chemotherapy improves the duration and quality of survival. These prostheses must be reserved to advanced malignant diseases with a rather long life expectancy.

ARTIFICIAL URETERAL REPLACEMENT FOR URETERAL NECROSIS AFTER RENAL TRANSPLANTATION: REPORT OF 3 CASES

Purpose We applied a new minimally invasive technique of artificial ureteral replacement for renal transplant ureteral necrosis. Materials and Methods Artificial ureteral replacement was performed in 3 renal transplant recipients with ureteral necrosis (complete in 1 and distal in 2) after failure of primary endoscopic treatment. Under fluoroscopic guidance a percutaneous tract is created and progressively dilated. The ureteral silicone polytetrafluoroethylene bonded tube is introduced into the pyelocaliceal renal graft cavities, tracked subcutaneously down to the suprapubic area and introduced into the bladder via a short incision. Results There were no immediate postoperative complications except for transient postoperative acute prostatitis in 1 patient. No secondary complications were observed with a mean followup of 2.5 years. All grafts have good late function and all tubes are patent with no evidence of encrustation or obstruction. The tubes are well tolerated underneath the skin. Reflux was present in all 3 cases with no clinical manifestation. An asymptomatic episode of lower urinary tract infection was observed in the female patient. Conclusions In select cases of ureteral necrosis after renal transplantation artificial ureteral replacement by subcutaneous pyelovesical bypass offers a possible alternative to open ureteral reconstruction.

Total ureteral replacement by subcutaneous pyelovesical bypass in ureteral necrosis after renal transplantation

Abstract Objectives: Ureteral necrosis is a rare complication of renal transplantation, and is seldom cured by endoscopic management alone. To avoid the potential hazard to the graft created by an open ureteral reconstruction in cases of renal transplant ureteral necrosis, we have appiled a new minimally invasive technique of total ureteral replacement, initially described for the palliative treatment of ureteral obstructions. The subcutaneous bypass technique is based on the use of a silicone-PTFE-bonded tube tunnelled underneath the skin. Methods: Total ureteral replacement by subcutaneous pyelovesical bypass was performed in three renal transplant patients (two men and one woman; mean age 41 years, (range 23–58) years with ureteral necrosis after failure of primary endoscopic treatment. The ureteral lesion was distal necrosis in two patients, and a total necrosis in the other. Under general anaesthesia and fluoroscopic guidance, a percutaneous tract was created and progressively dilated. The ureteral prosthesis was introduced into the pyelocaliceal cavities through a 30 F Amplatz sheet, then subcutaneously tracked down to the suprapubic area, and introduced into the bladder via a short incision. Results: There was no operative or postoperative morbidity. There was no obstruction, dislodgement or encrustation of the prosthesis. There were no bladder-related symptoms, or clinical reflux, and no abdominal wall complications. An asymptomatic episode of lower urinary tract infection (Staphylococcus epidermidis) was observed in the female patient. All the grafts were functioning with fine pyelocaliceal cavities, with a mean follow-up of 32 months (13–69 months). Conclusion: Total ureteral replacement by subcutaneous pyelovesical bypass is a simple and safe technique of ureteral reconstruction in renal transplantation. Late encrustation of the prosthesis may occur, and the prosthesis may need to be changed in such cases. Subcutaneous pyelovesical bypass can be regarded as an alternative to an open procedure to treat ureteral necrosis after renal transplantation.

Failure of ureteral replacement with gore-tex tube grafts

Objectives. To evaluate the role of polytetrafluoroethylene (Gore-Tex) as a ureteral substitute in dogs after resection of a 5 to 8-cm-long middle segment. Methods. Five mongrel dogs underwent resection of the middle segment of the left ureter and segmental replacement of the resected part with segments of Gore-Tex over a double-J catheter. The double-J stents were removed at 21 days and the dogs were evaluated by excretory urography and abdominal ultrasonography 12 weeks after surgery. They were then killed and the ureters and the kidneys examined both grossly and microscopically. Results. There was radiologic evidence of advanced hydronephrosis on the left side in all 5 dogs. Grossly, the left kidneys showed marked pelvic and proximal ureteral dilatation and atrophy of parenchyma. Severe stricture at the anastomotic sites and marked fibrous tissue around the prostheses were found. No cellular lining was found in the Gore-Tex lumen. Conclusions. There is no potential for ureteral replacement by Gore-Tex tube graft.

Surgical and endoscopic therapy

Despite the efficacy of new chemotherapy regimens, the medical treatment of genitourinary tubercolosis leads to recovery without sequelae in only 17–47% of cases. Open or endoscopic surgery therefore maintains an important role in treatment of the disease. Eighty years ago nephrectomy was the treatment of choice of renal tubercolosis. Nowadays some authors limit nephrectomy to patients with intractable pain, uncontrollable secondary infections, life-threatening hematuria, uncontrollable hypertension or resistance of the mycobacterium to medical therapy. We believe nephrectomy should be performed in cases of extensive renal damage, with or without complete functional loss, and in any case should be associated with exeresis of the whole ureter. In the presence of localised lesions, such as infundibular scarring with closed-off calyx, we generally perform a calycectomy in order to avoid a relapse of the disease and other possible complications. Also in these cases, however, surgery is controversial. Another aspect under debate concerns the association between chemotherapy and steroids. These stenoses, often involving the ureter, can be treated endoscopically (placement of ureteral stent, balloon dilatation, ureterotomy) or surgically (pyeloplasty, ureteral reimplantation, ileal ureter replacement, renal auto-transplantation). A serious consequence of urogenital tuberculosis is the loss of bladder capacity. This condition may be effectively treated with cytoplasty using an intestinal segment. In conclusion, conservative or radical surgery is still necessary to treat many cases of urogenital tubercolosis.

Subcutaneous Ureteral Replacement: A Canine Model

There are several clinical situations in which extrinsic or intrinsic ureteral diseases necessitate extensive reconstructive surgery. Unfortunately, not all patients are candidates for such surgery (e.g., those with retroperitoneal metastatic disease). Ureteral replacement is indicated in this selected group of patients. A viable option is to establish a ureteral replacement using subcutaneous tubes. Among the problems associated with this method of urine diversion are selecting the proper material for the tubes, the timing of tube replacement, encrustation and occlusion, urine reflux, and renal function. There is an obvious need for an animal model to address these issues. The aim of this study was to establish a reproducible canine model for subcutaneous ureteral replacement, by using a combination of nephrostomy and cystostomy tubes joined together under the skin. The animal study was conducted in 6 dogs. A pigtail nephrostomy and a cystostomy were inserted through a midline abdominal incision and stab wounds in the abdominal wall. A subcutaneous tract was bluntly made toward the nephrostomy incision starting from the cystostomy incision. The nephrostomy was grasped with the clamp and brought through the subcutaneous tunnel to the cystostomy incision. Upon emerging through the cystostomy incision, the tubes were joined and buried under the skin. Intravenous urography at 4-6 weeks postoperatively in 4 dogs showed no deterioration of renal function, but some hydronephrosis was present. Using the technique described in this paper, it is possible to establish a subcutaneous ureteral replacement using nephrostomy and cystostomy tubes in dogs. This model may serve for further research of the various questions associated with subcutaneous ureteral replacement in humans.

ILEAL URETER

Ureteral replacement with ileal bowel segments has become common in the armamentarium of the reconstructive urologist. The use of ileal bowel substitution, whether total or segmental, has provided yet another surgical alternative for renal preservation. The indications, surgical technique, and results with the ileal ureter are reviewed.

Free ureteral replacement in rats: regeneration of ureteral wall components in the acellular matrix graft

Objectives To evaluate ureteral replacement by a free homologous graft of acellular matrix in a rat model. Methods In 30 male Sprague-Dawley rats, a 0.3 to 0.8-cm midsegment of the left ureter was resected and replaced with an acellular matrix graft of equal length placed on a polyethylene stent. The animals were killed at varying intervals, and the grafted specimens were prepared for light and electron microscopy. Results In all animals, the acellular matrix graft remained in its original position without evidence of incrustation or infection, and histologic examination showed complete epithelialization and progressive infiltration by vessels. At 10 weeks, smooth muscle fibers were observed; at 12 weeks, nerve fibers were first detected; at 4 months, smooth muscle cells had assumed regular configuration. Conclusions The ureteral acellular matrix graft appears to promote the regeneration of all ureteral wall components.

Genitourinary tuberculosis in pediatric surgical practice

Background: Genitourinary tuberculosis (GUTB) has been reported to account for 20% to 73% of all cases of extrapul-monary tuberculosis in the general population but is much rarer in children. GUTB is a form of secondary tuberculosis with vague symptoms. Surgical intervention is required in a minority of cases. Methods: Nine cases of genitourinary tuberculosis (GUTB) were diagnosed and treated from 1988 to 1995. The age of the patients ranged from 5 to 12 years. There were five boys and four girls. Presenting features were diverse and included gross hematuria in 44% of cases and epididymoorchitis in 22% of cases. Rarer presenting features included acute renal failure, staghorn calculus, and pyonephrosis. Associated or past history of tuberculosis was present in three patients. Conclusive diagnosis was made on the basis of isolation of mycobacterium tuberculosis, histopathology, or cystoscopy in eight patients, whereas one patient was given a therapeutic trial based on clinical manifestations. Results: Response to antitubercular drug therapy was gratifying. Excisional surgery in the form of nephrectomy was needed in one patient, whereas another underwent bilateral ureteric replacement with ileal loops for multiple ureteric strictures. Conclusions: The wide variety of presenting features and pathological lesions that result from GUTB are emphasized. The diagnosis of GUTB must be suspected in patients who present with hematuria (gross or otherwise), epididymoorchitis, and patients with long segment or multiple ureteric strictures. In view of the anticipated resurgence in tuberculosis caused by the prevalence of aquired immunodeficiency syndrome the pediatric urologist must be aware of the pathophysiology and clinical spectrum of this disease.

Indications for surgical management of genitourinary tuberculosis.

The incidence of tuberculosis has risen in many parts of the world, and more attention is being focused on genitourinary tuberculosis (GT), the second most common extrathoracic form of tuberculosis. Although chemotherapy is the mainstay of treatment, ablative surgery as a first-line management may be unavoidable for sepsis or abscesses. In cases with hydronephrosis and progressive renal insufficiency caused by obstruction, renal drainage (by stenting or nephrostomy) must be performed immediately. In all other situations triple-drug chemotherapy should be undertaken for at least 6 months and stable conversion obtained before ablative or reconstructive surgery is planned. Nephrectomy or partial nephrectomy is indicated for nonfunctioning or poorly functioning kidneys, particularly if continuous flank pain or hypertension is present. Stenosis of the ureter usually can be managed by temporary stenting and adjuvant corticosteroid therapy. Today the indications for augmentation are rare, but bladder replacement may be combined with ureter replacement using segments of intestine.

Long-segment ureteral replacement with expanded polytetrafluoroethylene grafts

Objectives Traumatic loss of significant lengths of ureter all too often results in nephrectomy when vascularized pedicles of bowel or bladder fail or are not available for substitution. Historically, alloplastic replacement of ureters has failed due to obstruction, bioincompatibility, or graft migration. This study was undertaken to test the performance of ringed expanded polytetrafluoroethylene (PTFE) tube grafts as ureteral replacements in a canine model. Methods Eight female dogs underwent partial ureteral replacement with ringed PTFE tube grafts. An involuting anastomosis was used to anchor the graft to the bladder. The dogs were followed with intravenous urograms and Whitaker infusion pressure tests for up to 12 months. Results Six of 8 animals (75%) had preservation of excellent renal function with normal intravenous urograms and low Whitaker infusion pressures. One animal had mild hydronephrosis with an elevated infusion pressure. One animal died of spontaneous renal rupture secondary to obstruction at the ureteral-graft anastomosis. All other grafts were patent by histologic examination without encrustation or infection. Conclusions Although not suggested as first-line therapy after ureteral loss, expanded PTFE may have a use as a prosthetic ureteral replacement in situations where conventional surgical therapies are unsuccessful. This material appears to be biocompatible and the technique of bladder anastomosis described here prevented migration of the prosthesis.

Caliceal Fistula Formation Following Renal Transplantation: Management With Partial Nephrectomy and Ureteral Replacement

Caliceal Fistula Formation Following Renal Transplantation: Management With Partial Nephrectomy and Ureteral Replacement

Reversed Seromuscular Flaps in the Urinary Tract in Dogs

Reversed seromuscular flaps of ileum and standard bowel replacement procedures were performed in 16 dogs to evaluate their potential to decrease the likelihood of recognized complications in cases of standard bowel replacement. Of 12 dogs augmentation cystoplasty was done in 6 and ureteral replacement was done in 6. In each group 4 procedures were performed using reversed seromuscular flap, while the remaining 2 were done in the conventional manner (controls). All flap animals had partial to full re-epithelialization with transitional cells but they also had gross and microscopic evidence of flap contraction at the end of 6 months. In the flap augmentation group intravesical pressure measured preoperatively at bladder volumes of 30cc and 60cc averaged 25.8 and 45.8mm. Hg compared to sacrifice pressures of 56.7 and 80.8mm. Hg. Monthly serum blood urea nitrogen measurements were lower in reversed seromuscular flap animals compared to controls. An additional 4 dogs were studied to help elucidate the etiology of graft contraction, of which 2 underwent reversed seromuscular flap enterocystoplasty with no mucosal stripping while 2 had a procedure exposing intact intestinal serosa to the lumen of the bladder and urine. All of these animals demonstrated good re-epithelialization of the serosal surface with transitional cells as well as little or no evidence of flap fibrosis or contraction. Our results demonstrate that the use of reversed seromuscular flaps in the urinary tract in dogs results in good re-epithelialization of the serosal surface with transitional cells but also flap contraction. This fibrosis and scarring process is largely due to the trauma of mucosal stripping and not urine contact.

Extensive, obstructing sodium urate deposition on wall of isolated ileum for replacement of entire ureter

We report a rare case of obstructing sodium urate stones occurring in the form of extensive deposition on the wall of isolated ileum for replacement of the entire ureter. The stones were disintegrated and removed with a rigid ureteroscop e and an electrohydraulic lithotriptor. Hyperuriaciduria, excessive alkalization of urine and urinary stagnation due to reflux, mucous retention, and prostatic hyperplasia were considered as the etiologic factors in the stone formation.