Artificial ureters in renal transplantation

Design of a Mechatronics Model of Urinary Bladder and Realization and Evaluation of Its Prototype

Annually, there are many bladder cancer patients undergoing radical cystectomy (RC) with urinary diversion worldwide. Until 2019, intestinal cystoplasty is still the gold standard for bladder replacement, but this therapy is always associated with severe complications. An ideal bladder substitute without using intestinal tissue remains a challenge today. In this work, an artificial mechatronics bladder (AMB) as a brand new bladder replacement approach is developed. We studied the main physiological function characteristics of a natural urinary bladder from teaching books and relevant papers. According to these characteristics, we completed an overall design of AMB and made a prototype in lab. The prototype successfully realized the functions of a natural bladder in vitro. It can expand to store urine in real time when urine is flowing into it. It can send a urination alarm when it is fully filled and can void urine automatically after receiving remote control signals. According to relevant papers and our test experience, if the prototype could be smaller and lighter and manufactured with good biocompatibility materials such as PTFE, we think it is possible for AMB to be implanted in an animal's body, and we deduce AMB could realize the functions of a natural urinary bladder in vivo. After thorough validation from animal testing, we hope AMB can be a good clinical option for bladder removal patients in the future.

Spotlight - Management of pyelovesical bypass device stones

Pyelovesical bypass devices or artificial ureters have been described as a last resort in patients with long ureteral strictures that fail traditional endoscopic and open repair. Herein, we describe a 52-year-old female who had a Detour (Coloplast, Humlebaek, Denmark) pyelovesical bypass device inserted after an iatrogenic ischemic injury to the distal two-thirds of the left ureter during pelvic surgery for recurrent endometrial stromal sarcoma. Six months after placement of the device, she presented with gross hematuria and recurrent urinary tract infections (UTIs) and was found to have encrustation of the distal silicone tip of the Detour device within the bladder. This was managed with resection of the distal silicone tip and flexible ureteroscopy with holmium laser lithotripsy. Despite suppressive antibiotic therapy and medical therapy for hypercalciuria, she presented four years later with intraluminal encrustations in the proximal end of the device. This was successfully managed with flexible ureteroscopy with holmium laser lithotripsy. Therefore, this case illustrates the feasibility of flexible ureteroscopy and holmium laser lithotripsy of Detour device encrustations as long as the device is not kinked and it allows the passage of the flexible ureteroscope up to the calcifications. In addition, patients contemplating insertion of such devices should be counselled regarding the risk of recurrent infections and encrustations.

Optimal management of distal ureteric strictures following renal transplantation: a systematic review

Our objective was to define optimal management of distal ureteric strictures following renal transplantation. A systematic review on PubMed identified 34 articles (385 patients). Primary endpoints were success rates and complications of specific primary and secondary treatments (following failure of primary treatment). Among primary treatments (n = 303), the open approach had 85.4% success (95% CI 72.5-93.1) and the endourological approach had 64.3% success (95% CI 58.3-69.9). Among secondary treatments (n = 82), the open approach had 93.1% success (95% CI 77.0-99.2) and the endourological approach had 75.5% success (95% CI 62.3-85.2). The most common primary open treatment was ureteric reimplantation (n = 33, 81.8% success, 95% CI 65.2-91.8). The most common primary endourological treatment was dilation (n = 133, 58.6% success, 95% CI 50.1-66.7). Fourteen complications, including death (4 weeks post-op) and graft loss (12 days post-op), followed endourological treatment. One complication followed open treatment. This is the first systematic review to examine the success rates and complications of specific treatments for distal ureteric strictures following renal transplantation. Our review indicates that open management has higher success rates and fewer complications than endourological management as a primary and secondary treatment for post-transplant distal ureteric strictures. We also outline a post-transplant ureteric stricture evaluation and treatment algorithm.

Extra-anatomic stent (EAS) as a salvage procedure for transplant ureteric stricture

Ureteric stricture is the most common urological complication following renal transplantation. Management often involves endo-urological interventions and open surgery. The definitive treatment is surgical reconstruction to restore continuity. Where this is not possible or contra-indicated and a stent cannot be placed in the ureter, an extra-anatomic stent (EAS) could be used to bypass a complete ureteric obstruction. Using an existing nephrostomy tract, a percutaneous stent is placed in the kidney and is tunneled under the skin into the bladder establishing extra-anatomical urinary drainage. We report the use of a novel EAS system in a patient with transplant ureteric stricture when antegrade stent placement or surgical reconstruction was not possible.

Simultaneous bilateral subcutaneous pyelovesical bypass as a salvage procedure in refractory retroperitoneal fibrosis

Ureteral obstruction causing renal failure is the most common complication associated with retroperitoneal fibrosis (RPF). Initial management includes steroid therapy together with ureteral stenting. When these fail, ureterolysis is the recommended surgical procedure. However, this could be challenging and recurrence is common. The aim of the present case series was to assess the feasibility of inserting simultaneous bilateral subcutaneous pyelovesical bypass grafts (SPBGs) in patients presenting with RPF who had failed initial endourologic/surgical management.

Use of mitrofanoff and yang-monti techniques as ureteric substitution for severe schistosomal bilateral ureteric stricture: a case report and review of the literature

Distal ureteric stricture is a common complication of urinary schistosomiasis which is a disease more prevalent in the tropics and subtropics. The surgical management of this complication is more challenging when it affects more than half of both ureters. We report the case of a 17-year-old Nigerian with a long standing recurrent painless terminal hematuria associated with bilateral colicky loin pains. Ultrasound scan showed bilateral hydro ureters and hydro nephrosis with deranged biochemical renal function. The patient had bilateral tube nephrostomy and antibiotic therapy. Definitive bilateral ureteric substitution was done using Mitrofanoff technique for the right ureter and Yang-Montie technique for the left ureter. The patient′s renal function became normal and he was discharged home without complication. The related literatures were reviewed. Surgical nonurothelial ureteral substitution is necessary for long, extensive, severe bilateral ureteric strictures so as to prevent progressive renal damage and end stage renal failure.

Endourological management of ureteric strictures after kidney transplantation: Stenting the stent

The incidence of ureteric obstruction after kidney transplantation is 3–12.4%, and the most common cause is ureteric stenosis. The standard treatment remains open surgical revision, but this is associated with significant morbidity and potential complications. By contrast, endourological approaches such as balloon dilatation of the ureter, ureterotomy or long-term ureteric stenting are minimally invasive treatment alternatives. Here we discuss the available minimally invasive treatment options to treat transplant ureteric strictures, with an emphasis on long-term stenting. Using an example patient, we describe the use of a long-term new-generation ureteric metal stent to treat a transplant ureter where a mesh wire stent had been placed 5 years previously. The mesh wire stent was heavily encrusted throughout, overgrown by urothelium and impossible to remove. Because the patient had several previous surgeries, we first considered endourological solutions. After re-canalising the ureter and mesh wire stent by a minimally invasive procedure, we inserted a Memokath® (PNN Medical, Kvistgaard, Denmark) through the embedded mesh wire stent. This illustrates a novel method for resolving the currently rare but existing problem of ureteric mesh wire stents becoming dysfunctional over time, and for treating complex transplant ureteric strictures.

Successful salvage of kidney allografts threatened by ureteral stricture using pyelovesical bypass

Ureteral stricture is the most common urologic complication after renal transplantation. When endourologic management fails, open ureteral reconstruction remains the standard treatment. The complexity of some of these procedures makes it necessary to explore other means of repair. This study evaluated the intermediate-term outcome of subcutaneous pyelovesical bypass graft (SPBG) on renal transplant recipients. We reviewed 8 patients (6 male and 2 female; mean age 52 years) with refractory ureteral strictures postrenal transplantation, who received SPBG as salvage therapy. All patients failed endourologic management and half failed open management of their strictures. After a mean follow-up of 19.4 months, 7 out of 8 renal grafts have good function with mean GFR of 58.5 mL/min/1.73 m(2), without evidence of obstruction or infection. One patient lost his graft due to persistent infection of the SPBG and one patient developed a recurrent urinary tract infection managed with long-term antibiotics. SPBG offers a last resort in the treatment of ureteral stricture after renal transplantation refractory to conventional therapy.

Pyelovesical bypass graft for palliative management of malignant ureteric obstruction: optimizing the technique by percutaneous access to the bladder using a split Amplatz sheath

OBJECTIVES

To introduce a simple modification to the original technique of pyelovesical bypass graft placement to make the procedure more minimally invasive.

METHODS

During the study period 2 patients with malignant ureteric obstruction underwent pyelovesical bypass graft placement using Detour stent (Mentor-Porges). The technique simply comprised tract dilatation of the previously placed percutaneous nephrostomy to place the proximal end of the graft in the renal collecting system, making a subcutaneous tunnel from a 1-cm suprapubic incision to the flank area, percutaneous access to the bladder under fluoroscopic guide and placement of the distal end of the stent into the bladder through a split Amplatz sheath. The operative outcome was analyzed prospectively.

RESULTS

Both patients tolerated the procedures well with no intra- and postoperative complications. Renal function remained stable during the follow-up period with acceptable urine output through the urethra. Abdominal wall complications such as fistula formation or pain along the subcutaneous tract as well as stent encrustation did not occur during the follow-up period.

CONCLUSIONS

Despite our small sample size and short follow-up period, percutaneous access to the bladder using a split Amplatz sheath during placement of the Detour stent, may be considered as a promising simple modification to optimize the technique by obviating the need for open cystostomy incision.

Endourologic implants to treat complex ureteral stenosis after kidney transplantation

OBJECTIVE

To evaluate the safety and efficacy of nitinol stents and the Detour extra-anatomical ureteral bypass graft in treatment of ureteral stenosis after kidney transplantation.

PATIENTS AND METHODS

Eighteen kidney transplant recipients with complex stenosis caused by failure of primary treatment or with high surgical risk or a poorly functioning graft (serum creatinine concentration >2.5 mg/dL) were treated using antegrade percutaneous implantation of nitinol stents (n = 16) or extra-anatomical ureteral bypass grafts (n = 3); 1 patient was treated with both techniques.

RESULTS

Mean (range) follow-up of ureteral stents was 51.2 (3-118) months. Patency rate at last follow-up, resumption of dialysis therapy, or death was 75% (12 of 16 patients). In 4 patients (25%), stent occlusion developed, which was treated using a double-J catheter in 2 patients, stent removal and pyeloureterostomy using the native ureter in 1 patient, and implantation of an extra-anatomical bypass graft in 1 patient. Mean follow-up in patients with extra-anatomical ureteral bypass grafts was 32 (8-64) months. One patient developed a urinary tract infection, and another had encrustation with obstruction.

CONCLUSIONS

Use of nitinol ureteral stents and extra-anatomical ureteral bypass grafts is a safe and effective alternative to surgery for treatment of post-kidney transplantation ureteral stenosis in patients with chronic graft dysfunction, those at high surgical risk, and those in whom previous surgical treatment has failed.

[Surgical treatment of ureteral stenosis after kidney transplantation]

Ureteral stenosis is the most frequent complication after kidney transplantation. The diagnosis is based on an elevated creatinine level and a dilatation of the urinary cavity. The first step of the management is a urinary diversion with endo-ureteral prosthesis or a nephrostomy placement. The surgical gold standard is the pyelo-ureterostomy. This is a safe and efficient technique in the treatment of this complication. We describe the different surgical alternatives and the endo-urologic management of the stenosis.

Subcutaneous pyelovesical bypass as replacement for standard percutaneous nephrostomy for palliative urinary diversion: prospective evaluation of patient's quality of life

PURPOSE

To improve the quality of life of patients with palliative definitive percutaneous nephrostomy, we prospectively evaluated a subcutaneous ureteral bypass using a newly designed ureteral prosthesis.

PATIENTS AND METHODS

A series of 19 patients receiving 27 subcutaneous tubes in replacement for percutaneous nephrostomy were evaluated. The ureteral prosthesis (Detour), a silicone tube glued inside a polyester tube, is inserted percutaneously into the renal pelvis to replace an established nephrostomy, tunneled subcutaneously, and introduced into the bladder through a small incision. All patients were followed every 3 months for 18 months or until death from tumor. Quality of life was assessed using the EORTC QLC-30 questionnaire; ultrasonography, intravenous urography, or both were used to assess the position and patency of the tubes.

RESULTS

There was no failure of insertion and no operative or immediate complication. The mean follow-up was 7.8 months, 6.6 months for the 15 patients who died from their tumors and 1 year for the 4 patients still alive at the end of the study. Suprapubic parietal infection occurred in three patients with altered bladders (radiation cystitis or tumor progression). There was an improvement of the function scale as a result of the elimination of the external percutaneous tube and a parallel worsening of the symptom scale secondary to the progression of disease. Patient ratings of the global quality of life and satisfaction with the urinary diversion were improved because of the absence of the percutaneous tube.

CONCLUSION

The subcutaneous pyelovesical bypass provides a better quality of life than a standard percutaneous nephrostomy tube in terminally ill patients by making them external-tube free.

Extraanatomic stents for transplant ureteric stenosis

Surgical and standard endourology options are limited in transplant patients with severe ureteric stenosis, particularly when access to the transplant renal pelvis is limited. The use of a silicone-polytetrafluoroethelene (PTFE)-bonded extraanatomic urinary tract stent for urinary tract drainage is described in two patients. This technique of ureteric reconstruction in renal transplantation may be considered when standard approaches have failed. It appears to be safe when performed by radiologists and urologists with expertise in percutaneous renal access.