Ureteral replacement with a new synthetic material: Gore-Tex

Intestinal seromuscular tunneling: a novel method for ureteral replacement--an experimental design

BACKGROUND

Long-segment ureteral injuries may have different etiologies. Although multiple procedures have been previously used for ureteral replacement, none of them had optimum results, and replacement of long segments of injured ureter is still a challenging surgical problem. In this article, we have hypothesized that it may be possible to use intestinal seromuscular tunneling as a novel method for ureteral replacement.

METHODS

This experimental study was conducted on eight dogs. After cutting the ureter at about its mid-part and ligating the distal part, a 10-cm tunnel was made in the seromuscular layer of small intestine using a metallic probe, and a catheter was passed through it. Proximal and distal ends of the tunnel were anastomosed to proximal end of ureter and urinary bladder, respectively. After 8 weeks, the dogs were killed, and their whole urinary system was sent for histopathologic examinations.

RESULTS

No complication was noted during the post-op period. Histopathologic examinations confirmed that the seromuscular tunnel was well patent, lined by pseudostratified transitional epithelium and without any inflammatory reaction.

CONCLUSION

Our study shows that ureteral replacement by intestinal seromuscular tunneling is anatomically possible at least in animal model. However, more well-designed prospective studies are needed to confirm its long-term functional results.

The feasibility of ureteral tissue engineering using autologous veins: an orthotopic animal model with long term results

Background

In an earlier study we demonstrated the feasibility to create tissue engineered venous scaffolds in vitro and in vivo. In this study we investigated the use of tissue engineered constructs for ureteral replacement in a long term orthotopic minipig model. In many different projects well functional ureretal tissue was established using tissue engineering in animals with short-time follow up (12 weeks). Therefore urothelial cells were harvested from the bladder, cultured, expanded in vitro, labelled with fluorescence and seeded onto the autologous veins, which were harvested from animals during a second surgery. Three days after cell seeding the right ureter was replaced with the cell-seeded matrices in six animals, while further 6 animals received an unseeded vein for ureteral replacement. The animals were sacrificed 12, 24, and 48 weeks after implantation. Gross examination, intravenous pyelogram (IVP), H&E staining, Trichrome Masson’s Staining, and immunohistochemistry with pancytokeratin AE1/AE3, smooth muscle alpha actin, and von Willebrand factor were performed in retrieved specimens.

Results

The IVP and gross examination demonstrated that no animals with tissue engineered ureters and all animals of the control group presented with hydronephrosis after 12 weeks. In the 24-week group, one tissue engineered and one unseeded vein revealed hydronephrosis. After 48 weeks all tissue engineered animals and none of the control group showed hydronephrosis on the treated side. Histochemistry and immunohistochemistry revealed a multilayer of urothelial cells attached to the seeded venous grafts.

Conclusions

Venous grafts may be a potential source for ureteral reconstruction. The results of so far published ureteral tissue engineering projects reveal data up to 12 weeks after implantation. Even if the animal numbers of this study are small, there is an increasing rate of hydronephrosis revealing failure of ureteral tissue engineering with autologous matrices in time points longer than 3 months after implantation. Further investigations have to prove adequate clinical outcome and appropriate functional long-term results.

Alça intestinal invertida como substituto do ureter: estudo experimental em cães

OBJETIVO: Pesquisar a viabilidade da alça ileal invertida como substituto ureteral. MÉTODOS: Quarenta cães foram divididos em 5 grandes grupos de 8 animais, cada um subdividido em 2 subgrupos de acordo com a data do sacrifício (I - sacrifício em 12-15 dias de pós-operatório, e II - 60 dias de pós-operatório). Nos grupos A e B fez-se a substituição ureteral parcial com selo de íleo invertido, após abertura lateral do ureter direito com 2 (Grupo A) ou 4 cm (Grupo B) de extensão. Nos demais grupos fez-se a substituição do segmento completo do ureter usando-se um tubo de íleo invertido de comprimento equivalente ao segmento do ureter ressecado com 2cm (Grupo C) e 6cm (Grupos D e E) de extensão. A mucosa ileal foi removida por raspagem ou diérese. A permeabilidade ureteral foi testada por urografia excretora e por exploração anatômica com cateter após o sacrifício. As peças foram estudas histologicamente após preparação e coloração com hematoxilina-eosina. RESULTADOS: O número de animais com urografia normal após o seguimento foi: A-2, B-2, C-3, D-2 e E- 2. A histologia revelou que a serosa ileal se reveste com urotélio, não como decorrência de metaplasia, mas do crescimento a partir da borda da mucosa ureteral. CONCLUSÃO: Conclui-se que o íleo invertido não é um bom substituto ureteral.

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.

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.

Management of complete ureteral replacement. Experiences and review of the literature

The common treatment for patients with extensive damage to the ureter is complete ureteral replacement, combining Boari flap-psoas bladder hitch and downward mobilization of the involved kidney, with complete ideal replacement of the ureter, renal autotransplantation, of elective nephrectomy. Three case reports serve to describe two options of reconstructive treatment for complete ureteral replacement. The operative techniques, their limits, their postoperative results, and the treatment alternatives are discussed with due regard to recent literature. In the case of ileal replacement we have used a very short ileal segment to reduce the absorption surface of the ileal mucosa. Reflux prevention of the ileal segment was performed by creating an invaginated distal ileum nipple which was additionally fixed at the Boari flap by a third stapler row (auto suture TASS) to prevent potential nipple-gliding.

Neointimized Gore-Tex graft for ureteral prosthesis in the dog

OBJECTIVES

To determine the feasibility of replacing a ureteral segment with a neointimized Gore-Tex graft.

METHODS

Seven adult mongrel dogs underwent a two-stage operative procedure. The first procedure involved arterializing the graft to stimulate spread of a luminal neoendothelium by transmural capillary growth. Eight weeks after the initial procedure, a segment of the ipsilateral ureter was replaced with a segment of the neointimized graft.

RESULTS

Histologic evaluation of a portion of the graft removed during the second procedure demonstrated transmural neocapillary ingrowth in all grafts; however, there was no neoendothelial growth on the luminal surface. In 5 dogs the graft was occluded with blood clot and was not suitable for a ureteral prosthesis. In 2 dogs the graft was patent and was successfully incorporated into the urinary system. After 1 year of observation, both of these dogs maintained a patent ureter and had no evidence of hydronephrosis on intravenous urogram.

CONCLUSIONS

These data demonstrate that a Gore-Tex graft can be used as a ureteral prosthesis in the dog. The importance of preliminary arterialization, however, remains to be determined.

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.

Subcutaneous urinary diversions for palliative treatment of pelvic malignancies

PURPOSE

We developed 2 subcutaneous urinary diversion techniques, pyelovesical bypass and anterior cutaneous nephrostomy, to improve the quality of life of patients undergoing permanent palliative percutaneous nephrostomy.

MATERIALS AND METHODS

A total of 21 patients underwent either pyelovesical bypass (19) or anterior cutaneous nephrostomy (13). Technically, the percutaneous nephrostomy tube is replaced by a self-retaining expanded polytetrafluoroethylene-silicone tube tunneled underneath the skin. The distal extremity can be either introduced into the bladder, creating a pyelovesical bypass, or brought out directly through a cutaneous orifice, creating an anterior cutaneous nephrostomy.

RESULTS

No tube was dislodged and none became obstructed due to incrustation or angulation. Standard percutaneous nephrostomy was necessary in 1 patient in each group. Improvement in the quality of life was stressed by all patients. Pyelovesical bypass eliminates external drainage and anterior cutaneous nephrostomy performed when the bladder is no longer functional allows for the creation of a single, easily dressed anterior stoma.

CONCLUSIONS

Pyelovesical bypass and anterior cutaneous nephrostomy constitute valuable alternatives to standard permanent palliative percutaneous nephrostomy.

Subcutaneous urinary diversion utilizing a nephrovesical stent: a superior alternative to long-term external drainage?

OBJECTIVES

The use of external percutaneous nephrostomy drainage in patients with end-stage ureteral obstruction in whom ureteral stenting has failed presents significant compromises in the patient's quality of life. Toward this end, we present the initial experience in the United States with an intracorporeal nephrovesical stent.

METHODS

We performed successful subcutaneous urinary diversion in 2 patients with malignant, metastatic periureteral obstruction. Both patients had previously been managed with a chronic percutaneous nephrostomy that was both painful and inconvenient. The nephrovesical stent was inserted utilizing percutaneous access to both the kidney and bladder followed by creation of a subcutaneous tunnel between the two sites.

RESULTS

The nephrovesical stents are patent at 6 and 9 weeks postoperatively and both patients have had their nephrostomy tubes removed. Both patients have noted a marked improvement in their overall comfort and quality of life since the stent has been in place.

CONCLUSIONS

Subcutaneous urinary diversion with a nephrovesical stent provides effective urinary drainage and may improve the quality of life of patients with malignant metastatic ureteral obstruction. Further long-term studies are needed.

The prevalence and distribution of proliferative and metaplastic changes in normal appearing canine bladders

The prevalence and distribution of Brunn's nests, simple hyperplasia, simple squamous metaplasia, cystitis glandularis/cystica, atypical hyperplasia, and lymphocytic infiltration were studied by multiple histologic sections in 30 grossly normal urinary bladders obtained from a controlled population of dogs ranging in age from two to 14 years. The data were statistically analyzed using Fisher's exact test and logistic regression. A comparison of urothelial changes was made between dog and human. Brunn's nests were the most prevalent urothelial change and were observed at one or more locations in 80% of the cases. Simple hyperplasia was the second most common proliferative change and was observed at one or more locations in 66.7% of all cases. Brunn's nests (p less than 0.0001) and simple hyperplasia (p = .003) were significantly more likely to be found in the trigone. Simple squamous metaplasia was observed at one more more locations in 23.3% of all cases. Lymphocytic infiltration was observed in 20% of the animals; however, there was no statistically significant correlation between it and the urothelial changes. The trigone was by far the most common site (86.6% of all cases) for one or more lesions to be found. There was no evidence that inflammation was the cause of these urothelial changes. The data supports the concept that Brunn's nests, simple hyperplasia, and simple squamous metaplasia are normal variants of bladder urothelium in dogs and further that they are not precancerous changes. There was a similarity in prevalence, distribution, and significance of many urothelial changes between the dog and human which indicates that the dog is a good comparative model for studying diseases of the urinary bladder.

Ureteral replacement using collagen sponge tube grafts

The use of a collagen sponge tube graft as a material for segmental ureteral replacement was investigated. The structural design of the collagen sponge graft was achieved by cell culture on the matrix. MGH-U1 cells, derived from bladder cell carcinoma, were grown in vitro on the collagen sponge matrix with excellent biocompatibility and without evidence of cytotoxicity. The collagen sponge demonstrated biodegradability when implanted subcutaneously in dogs. However, a urine exposure test of collagen sponge in rat bladders revealed extensive salt deposits on its surface in some rats, as observed by crystallographic examination. Segmental ureteral replacements by collagen sponge tube grafts, accompanied by ureteral splint catheters, were performed in dogs. There was extensive uro-epithelial cell regeneration on the inner surface of the collagen grafts, without evidence of severe hydronephrosis, 5 to 12 weeks following the procedure. The results indicate the potential for ureteral replacement by collagen sponge tube grafts, which would act as non-toxic, biodegradable scaffolds inducing the regenerative activity of the ureter.

A preliminary in vivo assessment of acrylic acid graft-copolymers in the urinary tract

Polymers such as polyethylene, polytetrafluorethylene and polypropylene may be copolymerized with acrylic acid by radiation initiation to produce copolymers which are cationic hydrogels and thus possess physical properties different to the base polymers from which they are derived. The present preliminary study was undertaken to determine whether this class of material may have potential application for use within the urinary tract. Inserts of such copolymers in sheet form (5 mm. square) and their corresponding base polymers were placed in the bladders of male Wistar rats as free floating grafts and left in situ for 3 months. Stone formation and/or encrustation occurred on 12 of the 16 radiation graft copolymers and on 9 of 11 of the corresponding base polymers. The altered physical properties of the tested acrylic acid graft copolymers appear to offer no additional resistance to encrustation although their plasticity and ability to swell in water may provide some advantages over more conventional polymeric materials.

The artificial bladder: a historical review

The search for the ideal surgical replacement for all or part of the urinary collecting system continues. A wide variety of biologic and nonbiologic substitutes have been tried. Even though much experience has been gained in this area, the use of artificial material remains at an experimental level and needs further development. This review presents the history, problems, and developments of the replacement of the urinary bladder by nonbiologic materials.