- Email: [email protected]
Endourologic Implants to Treat Complex Ureteral Stenosis After Kidney Transplantation
Other Problems
Endourologic Implants to Treat Complex Ureteral Stenosis After Kidney Transplantation F.J. Burgos, G. Bueno, R. Gonzalez, J.J. Vazquez, V. Diez-Nicolás, R. Marcen, A. Fernández, and J. Pascual ABSTRACT Objective. To evaluate the safety and efficacy of nitinol stents and the Detour extraanatomical 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. RETERAL STENOSIS incidence after kidney transplantation ranges from 1% to 10%. In 75% of patients, the stricture is located at the level of the distal ureter and is a predictor of graft survival.1 Open surgery with ureterobladder reimplantation or pyeloureterostomy using the native ureter has been the treatment of choice. However, advances in interventional radiology and endourologic techniques have enabled percutaneous treatment of post– kidney transplantation ureteral stenosis. Balloon dilation
U
followed by placement of a double-J catheter for 4 to 8 weeks is successful in 38% to 80% of patients at 1-year follow-up.2,3 From the Departments of Urology (F.J.B., G.B., R.G., J.J.V., V.D.-N.) and Nephrology (R.M., A.F., J.P.), Hospital Ramon y Cajal, Universidad de Alcalá, Madrid, Spain. Address reprint requests to Dr F.J. Burgos, C/Doña Juana I. de Castilla 34, 28027 Madrid, Spain. E-mail: [email protected]
© 2009 Published by Elsevier Inc. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/09/$–see front matter doi:10.1016/j.transproceed.2009.06.068
Transplantation Proceedings, 41, 2427–2429 (2009)
2427
2428
Use of self-expanding metallic stents in the vascular, bile, and gastrointestinal tracts is well established. However, their use in treatment of benign and malignant ureteral obstruction in the urinary tract of native kidneys has been reported only rarely.4 –7 In particular, reports of use of metallic stents for resolution of post– kidney transplantation ureteral stenosis are limited,8 –14 and extra-anatomical ureteral bypass graft implantation has been used even more infrequently.15–18 PATIENTS AND METHODS From 1995 to 2007, we performed 560 kidney transplantation procedures. Sixteen metallic stents and 3 extra-anatomical ureteral bypass grafts were implanted in 18 recipients (12 men and 6 women; mean [SD] age, 54 [10.2] years) with ureteral stenosis; in 1 patient, sequential use of both implants was required. Indications for stent or bypass graft implantation were complex stenosis with failure of primary treatment, high surgical risk, or pooly functioning graft (serum creatinine concentration ⬎2.5 mg/dl). Stent implantation was considered the first choice of treatment in 40% of patients. Ureteral stenosis was located at the site of ureterovesical reimplantation in 11 patients, midureter in 5 patients, ureteropelvic junction in 1 patient, and pyeloureterostomy with native ureter in 1 patient. The extent of stenosis varied from 1.0 to 3.5 cm. Nitinol metallic stents (Sinuflex Optimed, Ettlingen, Germany) were used in 16 patients. Stent diameter was 4 mm in the first 2 patients and 8 mm in the last 14 patients, and stent length ranged from 1 to 4 cm. Implantation was always antegrade through a previous nephrostomy tract after passing a guide wire across the stricture and dilation with a balloon catheter. When the stenosis was located at the level of the ureterovesical junction, transurethral endoscopic control was used to prevent stent migration into the bladder cavity. Ureteral patency after stent implantation was confirmed at antegrade pyelography. Extra-anatomical ureteral bypass grafts (Detour Mentor, Porges, UK), made of Silicone with Dacron sleeves and with 26F diameter, were implanted in the kidney and bladder through a previous nephrostomy tract. A subcutaneous tunnel was created between the nephrostomy and the suprapubic areas with the Detour tunneling device. The bladder was minimally opened for catheter insertion. The Dacron sleeves were anchored to the bladder wall and parenchymal kidney tract to prevent migration of the bypass graft. Both stent and bypass graft implantation were performed using sedation and local anesthesia. Implant patency was evaluated at the last follow-up, resumption of dialysis therapy, or death. Patency was considered with reference to renal function or findings at ultrasonography or antegrade pyelography. Determination of serum creatinine concentration, urine culture, and ultrasonography of the graft were performed at 3-month intervals.
RESULTS
Mean (range) follow-up of ureteral stents was 51.2 (3–118) months. Twelve of 16 stents (75%) were patent, and 4 (25%) were obstructed at 2, 3, 4, and 6 months, respectively, after timplantation. In 2 patients, insertion of a double-J catheter enabled repermeabilization of the stent until resumption of dialysis therapy or death. In the other 2 patients, pyeloureterostomy with the recipient’s native ureter after stent removal or extra-anatomical bypass grafting was required. Mean creatinine concentration decreased by
BURGOS, BUENO, GONZALEZ ET AL
41% (14%– 63%). In 2 of 16 patients (12.5%), urine culture revealed an asymptomatic urinary tract infection caused by Escherichia coli or Pseudomonas aeruginosa. Significant hematuria developed in 1 patient, which resolved with conservative treatment. Mean follow-up of extra-anatomical ureteral bypass grafts was 32 (8 – 64) months. Two of 3 grafts (66%) remained patent at 8 and 64 months, respectively. In the third patient, obstruction developed secondary to an infected stone encrustation of the graft at 24 months. This obstruction was treated using laser lithotripsy via a cystoscopic approach. The patient who was followed up longest developed a urinary tract infection caused by P aeuroginosa that required prolonged antibiotic therapy. The 3 extra-anatomical ureteral bypass grafts currently are functioning. DISCUSSION
Ureteral obstruction develops in 1% to 10% of patients post– kidney transplantation. The treatment of choice is surgical repair with a new ureterocystostomy or ureteropyeloureterostomy to the recipient’s native ureter.1 Advances in percutaneous endourology have made transluminal treatment of ureteral structures safe and effective. Some patients at high surgical risk or with severe graft dysfunction who are not candidates for surgery can be treated with endourologic techniques. Balloon dilation followed by double-J catheter placement has a reported success rate of 38% to 80%.2,3,19 In the present study, use of nitinol (an alloy of nickel and titanium) stents to treat ureteral stenosis was effective in 75% of patients, with mean follow-up of 51 months. Implantation was always antegrade through a previous nephrostomy tract after passing a Terumo guide wire across the stenosis to dilate it with a balloon catheter. In patients with distal stenosis, it is mandatory that implantation be performed under bladder endoscopic control to prevent stent protrusion below the ureteral orifice, which, in theory, would increase the risk of encrustation.13,14 Obstruction of the stent from urothelial hyperplasia developed in 25% of our patients, usually early after implantation, and occurred more frequently with 4-mm stents than with 8-mm stents. Use of metallic stents for treatment of benign strictures has been reported rarely. The patency rate is approximately 70% at mean follow-up of 18 months.6,7,10 To our knowledge, few reports describe treatment of posttransplantation ureteral stenosis using metallic stents. Herrero et al8 first reported use of a 40-mm long, 6-mm-diameter Wallstent (Boston Scientific Corp, Natick, Mass) after balloon dilation to treat posttransplantation ureteral stenosis. They observed no incidence of obstruction, encrustration, or infection; however, they did not specify the duration of follow-up. Peregrin and Lacha9 reported the case of 1 patient with distal ureteral stenosis 10 mm in length that was treated using a Gianturco-Rosch double-segment 8-mm-diameter biliary metallic stent (Cook Medical Inc, Bloomington, Ind). After almost 3-year follow-up, the stent was patent. Kulkarni and Bellamy10 reported treatment of a
ENDOUROLOGIC IMPLANTS IN URETERAL STENOSIS
ureteral stricture using a 10F Memokath metallic stent (Pnn Medical A/S, Kvistgaard, Denmark). Boyvat et al12 observed 4 patients with recurrent ureteral stenosis that was treated using implantation of a Memokath stent. After 20 months of follow-up, 2 stents were removed because of migration and chronic infection, respectively. Cantasdemir et al11 reported resolution at 3-year follow-up of ureteral stenosis unresponsive to balloon dilation after living-donor transplantation using a Memotherm stent (Angiomed GmbH & Co). However, metallic ureteral stents should not be considered the first option for treatment of ureter obstruction. Inasmuch as long-term patency has not been clearly established, only kidney transplant recipients with severe chronic graft obstruction or patients at high surgical risk should be treated using these stents. Extra-anatomical diversion using a subcutaneously placed tunneled stent has been reported.15–18 Our limited experience in 3 cases with 32-month follow-up demonstrated that long-term use of these implants is associated with urinary tract infection and encrustation, although the 3 bypass grafts are currently patent. Desgrandchamps et al16 also reported posttransplantation ureteral necrosis in 3 patients that was treated using subcutaneous artificial ureteral replacement as a pyelovesical bypass graft. The device was composed of an inner Silicone layer and an outer polytetrafluoroethylene layer. After a mean follow-up of 32 months, no obstruction or encrustation had developed. Andonian et al17 reported ureteral strictures in 2 kidney transplant recipients with ureteral strictures that were treated using Siliconepolyester pyelovesical bypass grafts. After 15-month followup, there was no evidence of obstruction, and renal function was stable. In conclusion, surgery is always the first choice for treatment of ureteral stenosis. However, in patients at high surgical risk with chronic deterioration of graft function or after previous failed surgery, alternative treatment with implantation of a metallic stent or an extra-anatomical bypass graft is safe and effective. REFERENCES 1. Gibbons WS, Barry JM, Hefty TR, et al: Complications following unstented parallel incision extravesical ureteroneocystostomy in 1000 kidney transplants. J Urol 148:38, 1992
2429 2. Kim KC, Banner MP, Ramchamdami P, et al: Balloon dilatation of ureteral strictures after renal transplantation. Radiology 186:717, 1993 3. Jones JW, Hunter DR, Matas AJ, et al: Successful percutaneous treatment of ureteral stenosis after renal transplantation. Transplant Proc 25:1038, 1993 4. Lugmayr HF, Pauer W: Wallstents for the treatment of extrinsic malignant ureteral obstruction: midterm results. Radiology 198:1051, 1996 5. Pauer W, Lugmayr HF: Metallic Wallstent: a new therapy for extrinsic ureteral obstruction. J Urol 148:281, 1992 6. Arya M, Mostafid HR, Patel MJ, et al: The self-expanding metallic ureteric stent in the long-term management of benign ureteric strictures. BJU Int 88:339, 2001 7. Burgos FJ, Linares A, Gómez V, et al: Efficacy of selfexpanding metallic stents for treatment of ureteral obstruction. Eur Urol 39(suppl 5):86, 2001 8. Herrero JA, Lezana A, Gallego J, et al: Self-expanding metallic stent in the treatment of ureteral obstruction after renal transplantation. Nephrol Dial Transplant 11:887, 1996 9. Peregrin JH, Lacha J: Successful treatment of renal transplant ureter stenosis with use of biliary Z stent. J Vasc Intervent Radiol 9:741, 1998 10. Kulkarni R, Bellamy E: Nickel-titanium shape memory alloy Memokath 051 ureteral stent for managing long-term ureteral obstruction: 4-year experience. J Urol 166:1750, 2001 11. Cantasemir M, Kantarci F, Numan F, et al: Renal transplant ureteral stenosis: treatment by self-expanding metallic stent. Cardiovasc Intervent Radiol 26:85, 2003 12. Boyvat F, Aytekin C, Colak T, et al: Memokath metallic stent in the treatment of transplant kidney ureter stenosis or occlusion. Cardiovasc Intervent Radiol 28:326, 2005 13. Pozo B, Burgos FJ, Linares A, et al: Estenosis ureteral postrasplante renal: tratamiento con prótesis metálica autoexpandible. Actas Urol Esp 27:190, 2003 14. Burgos FJ, Pascual J, Marcen R, et al: Self-expanding ureteral stents for treatment of ureteral stenosis after kidney transplantation. Transplant Proc 37:3828, 2005 15. Perez P, Pozo B, Burgos FJ, et al: Derivación urinaria extraanatomica mediante catéter subcutáneo. Actas Urol Esp 28:314, 2004 16. Desgrandchamps F, Paulhac P, Fornairon S, et al: Artificial ureteral replacement for ureteral necrosis alter renal transplantation: Report of 3 cases. J Urol 159:1830, 1998 17. Andonian S, Zom K, Paraskevas S, et al: Artificial ureters in renal transplantation. Urology 66:1109, 2005 18. Minhas S, Irving H, Lloyd S, et al: Extra-anatomic stents in ureteric obstruction: experience and complications. BJU Int 84: 762, 1999
Endourologic Implants to Treat Complex Ureteral Stenosis After Kidney Transplantation F.J. Burgos, G. Bueno, R. Gonzalez, J.J. Vazquez, V. Diez-Nicolás, R. Marcen, A. Fernández, and J. Pascual ABSTRACT Objective. To evaluate the safety and efficacy of nitinol stents and the Detour extraanatomical 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. RETERAL STENOSIS incidence after kidney transplantation ranges from 1% to 10%. In 75% of patients, the stricture is located at the level of the distal ureter and is a predictor of graft survival.1 Open surgery with ureterobladder reimplantation or pyeloureterostomy using the native ureter has been the treatment of choice. However, advances in interventional radiology and endourologic techniques have enabled percutaneous treatment of post– kidney transplantation ureteral stenosis. Balloon dilation
U
followed by placement of a double-J catheter for 4 to 8 weeks is successful in 38% to 80% of patients at 1-year follow-up.2,3 From the Departments of Urology (F.J.B., G.B., R.G., J.J.V., V.D.-N.) and Nephrology (R.M., A.F., J.P.), Hospital Ramon y Cajal, Universidad de Alcalá, Madrid, Spain. Address reprint requests to Dr F.J. Burgos, C/Doña Juana I. de Castilla 34, 28027 Madrid, Spain. E-mail: [email protected]
© 2009 Published by Elsevier Inc. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/09/$–see front matter doi:10.1016/j.transproceed.2009.06.068
Transplantation Proceedings, 41, 2427–2429 (2009)
2427
2428
Use of self-expanding metallic stents in the vascular, bile, and gastrointestinal tracts is well established. However, their use in treatment of benign and malignant ureteral obstruction in the urinary tract of native kidneys has been reported only rarely.4 –7 In particular, reports of use of metallic stents for resolution of post– kidney transplantation ureteral stenosis are limited,8 –14 and extra-anatomical ureteral bypass graft implantation has been used even more infrequently.15–18 PATIENTS AND METHODS From 1995 to 2007, we performed 560 kidney transplantation procedures. Sixteen metallic stents and 3 extra-anatomical ureteral bypass grafts were implanted in 18 recipients (12 men and 6 women; mean [SD] age, 54 [10.2] years) with ureteral stenosis; in 1 patient, sequential use of both implants was required. Indications for stent or bypass graft implantation were complex stenosis with failure of primary treatment, high surgical risk, or pooly functioning graft (serum creatinine concentration ⬎2.5 mg/dl). Stent implantation was considered the first choice of treatment in 40% of patients. Ureteral stenosis was located at the site of ureterovesical reimplantation in 11 patients, midureter in 5 patients, ureteropelvic junction in 1 patient, and pyeloureterostomy with native ureter in 1 patient. The extent of stenosis varied from 1.0 to 3.5 cm. Nitinol metallic stents (Sinuflex Optimed, Ettlingen, Germany) were used in 16 patients. Stent diameter was 4 mm in the first 2 patients and 8 mm in the last 14 patients, and stent length ranged from 1 to 4 cm. Implantation was always antegrade through a previous nephrostomy tract after passing a guide wire across the stricture and dilation with a balloon catheter. When the stenosis was located at the level of the ureterovesical junction, transurethral endoscopic control was used to prevent stent migration into the bladder cavity. Ureteral patency after stent implantation was confirmed at antegrade pyelography. Extra-anatomical ureteral bypass grafts (Detour Mentor, Porges, UK), made of Silicone with Dacron sleeves and with 26F diameter, were implanted in the kidney and bladder through a previous nephrostomy tract. A subcutaneous tunnel was created between the nephrostomy and the suprapubic areas with the Detour tunneling device. The bladder was minimally opened for catheter insertion. The Dacron sleeves were anchored to the bladder wall and parenchymal kidney tract to prevent migration of the bypass graft. Both stent and bypass graft implantation were performed using sedation and local anesthesia. Implant patency was evaluated at the last follow-up, resumption of dialysis therapy, or death. Patency was considered with reference to renal function or findings at ultrasonography or antegrade pyelography. Determination of serum creatinine concentration, urine culture, and ultrasonography of the graft were performed at 3-month intervals.
RESULTS
Mean (range) follow-up of ureteral stents was 51.2 (3–118) months. Twelve of 16 stents (75%) were patent, and 4 (25%) were obstructed at 2, 3, 4, and 6 months, respectively, after timplantation. In 2 patients, insertion of a double-J catheter enabled repermeabilization of the stent until resumption of dialysis therapy or death. In the other 2 patients, pyeloureterostomy with the recipient’s native ureter after stent removal or extra-anatomical bypass grafting was required. Mean creatinine concentration decreased by
BURGOS, BUENO, GONZALEZ ET AL
41% (14%– 63%). In 2 of 16 patients (12.5%), urine culture revealed an asymptomatic urinary tract infection caused by Escherichia coli or Pseudomonas aeruginosa. Significant hematuria developed in 1 patient, which resolved with conservative treatment. Mean follow-up of extra-anatomical ureteral bypass grafts was 32 (8 – 64) months. Two of 3 grafts (66%) remained patent at 8 and 64 months, respectively. In the third patient, obstruction developed secondary to an infected stone encrustation of the graft at 24 months. This obstruction was treated using laser lithotripsy via a cystoscopic approach. The patient who was followed up longest developed a urinary tract infection caused by P aeuroginosa that required prolonged antibiotic therapy. The 3 extra-anatomical ureteral bypass grafts currently are functioning. DISCUSSION
Ureteral obstruction develops in 1% to 10% of patients post– kidney transplantation. The treatment of choice is surgical repair with a new ureterocystostomy or ureteropyeloureterostomy to the recipient’s native ureter.1 Advances in percutaneous endourology have made transluminal treatment of ureteral structures safe and effective. Some patients at high surgical risk or with severe graft dysfunction who are not candidates for surgery can be treated with endourologic techniques. Balloon dilation followed by double-J catheter placement has a reported success rate of 38% to 80%.2,3,19 In the present study, use of nitinol (an alloy of nickel and titanium) stents to treat ureteral stenosis was effective in 75% of patients, with mean follow-up of 51 months. Implantation was always antegrade through a previous nephrostomy tract after passing a Terumo guide wire across the stenosis to dilate it with a balloon catheter. In patients with distal stenosis, it is mandatory that implantation be performed under bladder endoscopic control to prevent stent protrusion below the ureteral orifice, which, in theory, would increase the risk of encrustation.13,14 Obstruction of the stent from urothelial hyperplasia developed in 25% of our patients, usually early after implantation, and occurred more frequently with 4-mm stents than with 8-mm stents. Use of metallic stents for treatment of benign strictures has been reported rarely. The patency rate is approximately 70% at mean follow-up of 18 months.6,7,10 To our knowledge, few reports describe treatment of posttransplantation ureteral stenosis using metallic stents. Herrero et al8 first reported use of a 40-mm long, 6-mm-diameter Wallstent (Boston Scientific Corp, Natick, Mass) after balloon dilation to treat posttransplantation ureteral stenosis. They observed no incidence of obstruction, encrustration, or infection; however, they did not specify the duration of follow-up. Peregrin and Lacha9 reported the case of 1 patient with distal ureteral stenosis 10 mm in length that was treated using a Gianturco-Rosch double-segment 8-mm-diameter biliary metallic stent (Cook Medical Inc, Bloomington, Ind). After almost 3-year follow-up, the stent was patent. Kulkarni and Bellamy10 reported treatment of a
ENDOUROLOGIC IMPLANTS IN URETERAL STENOSIS
ureteral stricture using a 10F Memokath metallic stent (Pnn Medical A/S, Kvistgaard, Denmark). Boyvat et al12 observed 4 patients with recurrent ureteral stenosis that was treated using implantation of a Memokath stent. After 20 months of follow-up, 2 stents were removed because of migration and chronic infection, respectively. Cantasdemir et al11 reported resolution at 3-year follow-up of ureteral stenosis unresponsive to balloon dilation after living-donor transplantation using a Memotherm stent (Angiomed GmbH & Co). However, metallic ureteral stents should not be considered the first option for treatment of ureter obstruction. Inasmuch as long-term patency has not been clearly established, only kidney transplant recipients with severe chronic graft obstruction or patients at high surgical risk should be treated using these stents. Extra-anatomical diversion using a subcutaneously placed tunneled stent has been reported.15–18 Our limited experience in 3 cases with 32-month follow-up demonstrated that long-term use of these implants is associated with urinary tract infection and encrustation, although the 3 bypass grafts are currently patent. Desgrandchamps et al16 also reported posttransplantation ureteral necrosis in 3 patients that was treated using subcutaneous artificial ureteral replacement as a pyelovesical bypass graft. The device was composed of an inner Silicone layer and an outer polytetrafluoroethylene layer. After a mean follow-up of 32 months, no obstruction or encrustation had developed. Andonian et al17 reported ureteral strictures in 2 kidney transplant recipients with ureteral strictures that were treated using Siliconepolyester pyelovesical bypass grafts. After 15-month followup, there was no evidence of obstruction, and renal function was stable. In conclusion, surgery is always the first choice for treatment of ureteral stenosis. However, in patients at high surgical risk with chronic deterioration of graft function or after previous failed surgery, alternative treatment with implantation of a metallic stent or an extra-anatomical bypass graft is safe and effective. REFERENCES 1. Gibbons WS, Barry JM, Hefty TR, et al: Complications following unstented parallel incision extravesical ureteroneocystostomy in 1000 kidney transplants. J Urol 148:38, 1992
2429 2. Kim KC, Banner MP, Ramchamdami P, et al: Balloon dilatation of ureteral strictures after renal transplantation. Radiology 186:717, 1993 3. Jones JW, Hunter DR, Matas AJ, et al: Successful percutaneous treatment of ureteral stenosis after renal transplantation. Transplant Proc 25:1038, 1993 4. Lugmayr HF, Pauer W: Wallstents for the treatment of extrinsic malignant ureteral obstruction: midterm results. Radiology 198:1051, 1996 5. Pauer W, Lugmayr HF: Metallic Wallstent: a new therapy for extrinsic ureteral obstruction. J Urol 148:281, 1992 6. Arya M, Mostafid HR, Patel MJ, et al: The self-expanding metallic ureteric stent in the long-term management of benign ureteric strictures. BJU Int 88:339, 2001 7. Burgos FJ, Linares A, Gómez V, et al: Efficacy of selfexpanding metallic stents for treatment of ureteral obstruction. Eur Urol 39(suppl 5):86, 2001 8. Herrero JA, Lezana A, Gallego J, et al: Self-expanding metallic stent in the treatment of ureteral obstruction after renal transplantation. Nephrol Dial Transplant 11:887, 1996 9. Peregrin JH, Lacha J: Successful treatment of renal transplant ureter stenosis with use of biliary Z stent. J Vasc Intervent Radiol 9:741, 1998 10. Kulkarni R, Bellamy E: Nickel-titanium shape memory alloy Memokath 051 ureteral stent for managing long-term ureteral obstruction: 4-year experience. J Urol 166:1750, 2001 11. Cantasemir M, Kantarci F, Numan F, et al: Renal transplant ureteral stenosis: treatment by self-expanding metallic stent. Cardiovasc Intervent Radiol 26:85, 2003 12. Boyvat F, Aytekin C, Colak T, et al: Memokath metallic stent in the treatment of transplant kidney ureter stenosis or occlusion. Cardiovasc Intervent Radiol 28:326, 2005 13. Pozo B, Burgos FJ, Linares A, et al: Estenosis ureteral postrasplante renal: tratamiento con prótesis metálica autoexpandible. Actas Urol Esp 27:190, 2003 14. Burgos FJ, Pascual J, Marcen R, et al: Self-expanding ureteral stents for treatment of ureteral stenosis after kidney transplantation. Transplant Proc 37:3828, 2005 15. Perez P, Pozo B, Burgos FJ, et al: Derivación urinaria extraanatomica mediante catéter subcutáneo. Actas Urol Esp 28:314, 2004 16. Desgrandchamps F, Paulhac P, Fornairon S, et al: Artificial ureteral replacement for ureteral necrosis alter renal transplantation: Report of 3 cases. J Urol 159:1830, 1998 17. Andonian S, Zom K, Paraskevas S, et al: Artificial ureters in renal transplantation. Urology 66:1109, 2005 18. Minhas S, Irving H, Lloyd S, et al: Extra-anatomic stents in ureteric obstruction: experience and complications. BJU Int 84: 762, 1999