Holmium: YAG laser endoureterotomy for ureterointestinal strictures

PURPOSE: The management of ureterointestinal stricture in patients who have undergone urinary diversion can be challenging. Endourological techniques have been increasingly used in recent years for ureteral stricture. While long-term results may not be as reliable or durable as those of traditional open reconstructive surgical techniques, associated morbidity is much less. The holmium (Ho):YAG laser, which has cutting and coagulating properties, has been demonstrated to have many applications in urology. We report our experience with and long-term results of Ho:YAG laser endoureterotomy for ureterointestinal strictures. MATERIALS AND METHODS: We reviewed the charts and followup history of 23 patients in whom the Ho:YAG laser was used to treat ureterointestinal anastomotic stricture. Strictures were treated percutaneously via the antegrade approach with flexible endoscopes and the holmium laser. A reversed 12/6Fr endopyelotomy stent was left indwelling for 6 weeks postoperatively. Success was defined as symptomatic improvement and radiographic resolution of obstruction. RESULTS: Between 1993 and 2000, 23 patients with a mean age of 61 years underwent endo-ureterotomy using the Ho:YAG laser for 24 ureterointestinal stricture. An overall success rate of 71% (17 of 24 cases) was achieved at a mean followup of 22 months. The success rate of holmium laser endoureterotomy for ureterointestinal stricture at 1, 2 and 3 years was 85%, 72% and 56%, respectively. Seven patients had recurrent strictures of which 4 developed 16 months or more postoperatively. No complications were noted. CONCLUSIONS: Ho:YAG laser endoureterotomy for ureterointestinal stricture disease is a minimally invasive endourological procedure that may provide more durable results than other modalities used for endoureterotomy. The Ho:YAG laser with its ability to cut tissue precisely and provide hemostasis combined with its versatility and compatibility with flexible endoscopes is an ideal instrument for safely performing endoureterotomy.     

Transplant ureter stricture: Acucise endoureterotomy and balloon dilation are effective

PATIENTS AND METHODS: Eight patients with ureteral stricture after renal transplantation underwent minimally invasive treatment with Acucise incision or balloon dilation. Acucise endoureterotomy was used to treat four patients with strictures at the ureterovesical anastomosis, and balloon dilation was used to treat four patients with a ureteroureterostomy stricture. Success was defined as an acceptable serum creatinine concentration in the absence of hydronephrosis with at least 1 year of follow-up. RESULTS: Acucise endoureterotomy for ureterovesical anastomosis stricture was successful in two of three patients (67%) with a mean follow-up of 20 months. One patient had an indeterminate outcome. Balloon dilation of strictured ureteroureterostomy was successful in three of four patients (75%) with a mean follow-up of 23.7 months. Three of the four patients with previously failed open revision were treated successfully with endourologic techniques. The two patients in whom treatment failed had strictures >/=1.5 cm and manifested comorbidities including diabetes mellitus. CONCLUSION: As our results are comparable to those of other published series, endourologic management of transplant ureteral stenosis is a reasonable strategy.     

输尿管镜钬激光内切开术治疗输尿管狭窄

目的探讨输尿管镜钬激光内切开术治疗输尿管狭窄的疗效。方珐本组10例输尿管狭窄，狭窄位于输尿管上段6例，中段1例，下段3例，输尿管狭窄段长度为0．3—1．8cm，采用输尿管镜钬激光（200μm激光光纤，输出能量0．8—1．0J，脉冲频率10-15Hz）内切开术治疗，术后留置1根或2根F5双J支架管，2～3个月后拔管。蛄杲手术时间30-50min，平均42min，无严重并发症，1例手术失败，余9例随访5—15个月，平均9．5个月，8例效果满意，1例术后3个月复发。站论输尿管镜钬激光内切开术治疗输尿管狭窄具有创伤小、并发症少、恢复快等优点，是一种安全、有效的微创手术方式。     

Percutaneous placement of permanent metal stents for treatment of ureteroenteric anastomotic strictures

PURPOSE: To evaluate the efficacy of permanent metal stent placement in the treatment of ureteroenteric anastomotic strictures following failed balloon dilation or laser endoureterotomy. PATIENTS AND METHODS: Metal stents were placed in six ureteroenteric anastomotic strictures in four patients presenting with recurrent obstruction after balloon dilation or laser endoureteromy. Patients were evaluated at 1 week postoperatively with antegrade ureterography and at 3 to 6 months with renal ultrasound or CT scans. Serum creatinine assays and physical examination were performed at serial postoperative clinic visits. RESULTS: At 1-week follow-up, antegrade studies demonstrated a patent anastomosis in all six strictures. With a mean follow-up of 10 months (range 7-12 months), no stricture recurrence has been seen. All patients have been clinically stable, without episodes of pyelonephritis, flank pain, or need for indwelling stents or nephrostomy tube placement. Serum creatinine concentrations have been stable in all patients. CONCLUSIONS: Metal stents offer a useful treatment option in patients who develop ureteroenteric anastomotic strictures after urinary diversion. Further, such stents may be used in patients failing balloon dilation or laser endoureterotomy. Further study to assess the long-term durability of metal stent placement is needed.     

腔内切开治疗移植肾输尿管膀胱吻合口梗阻

目的 探讨腔内切开处理移植肾输尿管膀胱吻合口梗阻的安全性与有效性. 方法 18例肾移植患者术后2～18个月出现尿量减少.实验室检查SCr 230～570/μmol/L.超声检查提示中重度肾积水.膀胱镜检查18例均无法逆行输尿管置管.经皮肾造瘘后行顺行造影显示输尿管膀胱吻合口梗阻,不完全梗阻14例、完全梗阻(闭锁)4例,梗阻长度0.5～1.3 cm.术中先经皮肾通道入镜,将斑马导丝顺行插过梗阻段达膀胱,再逆行经尿道将膀胱内导丝拉出尿道外,直视下用电刀或钬激光全层切开梗阻段;若斑马导丝无法通过梗阻段,则采用造影剂混合美蓝充盈膀胱,顺行入镜到达梗阻处,X线监视下用长针向膀胱内穿刺打通.术后留置2条双J管6～8周,定期行超声、肾图和肾功能检查. 结果 18例术中见吻合口黏膜苍白水肿,管壁僵硬、管腔狭窄、瘢痕组织增生明显,均成功将梗阻段切开,无手术并发症发生.术后夹闭肾造瘘管后排尿通畅,尿量正常.实验室复查SCr降至87～233μmol/L.超声检查提示肾血流正常,肾积水消失或仅轻度积水.随访4～90个月,平均51个月.8例1次治疗成功;5例因瘢痕组织切除不彻底经再次腔内切开(3例2次,2例3次)治疗后成功;5例拔管后梗阻复发无法逆行入镜,梗阻难以处理改开放手术治疗,其中4例治疗成功,1例仍需长期输尿管置管. 结论 肾移植术后输尿管膀胱吻合口梗阻采用腔内切开治疗安全、有效,梗阻复发者可考虑再次内切开或开放手术治疗.     

输尿管镜钬激光内切开术治疗输尿管狭窄疗效分析

目的:探讨输尿管镜下钬激光内切开术治疗输尿管狭窄的临床疗效.方法:采用经输尿管镜钬激光内切开术治疗输尿管狭窄患者31例,术中留置F8双J管,术后2～3个月拔取双J管.结果:术后共随访28例,时间3～28个月.23例治愈,治愈率为82.1%(23/28).结论:输尿管镜钬激光内切开术治疗输尿管狭窄是一种疗效确切、安全微创的手术方法.     

经皮肾穿刺顺行球囊扩张治疗移植肾输尿管梗阻

目的探讨经皮肾穿刺顺行球囊扩张治疗移植肾输尿管梗阻的安全性和疗效。方法回顾性分析2007年至2011年华中科技大学附属协和医院6例接受经皮肾穿刺顺行球囊扩张治疗移植肾输尿管梗阻的患者资料。所有患者先行B超引导移植肾穿刺造瘘,顺行造影确定梗阻的具体位置,顺行球囊扩张输尿管狭窄段,术后留置双J管和肾造瘘管,无效则改开放手术。结果6例患者中1例输尿管狭窄段〉1cm,球囊扩张失败,1例合并尿瘘,尿囊肿,扩张治疗无效,此2例均经开放手术治愈;其余4例一次扩张治愈,随访16～38个月,肾功能正常,无梗阻复发。结论经皮肾穿刺顺行球囊扩张安全、损伤小,可作为治疗移植肾输尿管梗阻的首选方法,对于合并有其他外科并发症或扩张治疗失败的患者,需开放手术治疗。     

Holmium: YAG laser endoureterotomy for treatment of ureteral stricture

Objectives

Endourologic techniques ranging from balloon dilation to endoincision with electrocautery, cold knife, and lasers have been increasingly used in recent years for the treatment of ureteral strictures. While the long-term results may not be as reliable or as durable as traditional reconstructive surgical techniques, they can be accomplished with much less morbidity. Recently, the holmium:yttrium-aluminum-garnet (YAG) laser, which possesses both cutting and coagulating properties, has been demonstrated to have many applications in urology. We report our experience with this laser in the endoscopic treatment of ureteral strictures.

Methods

We reviewed the charts and follow-up history of 22 patients in whom the holmium:YAG laser was used to treat ureteral strictures from a variety of causes and including those in ureteroenteric anastomoses. Strictures were either approached in a retrograde fashion with a 6.9F ureteroscope or antegrade with flexible instruments in the cases involving ureteroenteric strictures. The only energy source employed was the laser, followed by balloon dilation. Indwelling stents were left in place for at least 4 weeks postoperatively and follow-up was obtained with radiographic imaging.

Results

A minimum 9-month follow-up was available for 18 patients. There were 5 patients who had developed recurrent strictures and were therefore considered treatment failures. Each of these patients failed in less than 3 months and all had either lengthy or complex strictures noted at the time of surgery. One patient was lost to follow-up and three recent patients have follow-up of 3 to 6 months showing no evidence of recurrent stricture formation. Overall, 16 of 21 (76%) patients are clinically well with no evidence of stricture recurrence.

Conclusions

Endoureterotomy for ureteral stricture disease is a minimally invasive, less morbid, but ultimately less successful, alternative to open surgical reconstruction. Stricture length and etiology remain the most important determinants of success. The holmium:YAG laser, with its ability to precisely cut tissue and provide hemostasis and its multiuse potential and compatibility with small rigid and flexible endoscopic instruments, is an ideal tool for performing endoureterotomy.     

Minimally Invasive Approach to Ureteral Stricture in Transplant Kidney by Periodic Retrograde Ureteral Stent Placement and Exchange

Purpose

The aim of the study was to evaluate the effectiveness of minimally invasive treatment of ureteral strictures and describe the technique that we used for retrograde placement of ureteral stent in transplant kidneys.

Endoscopic treatment of ureteric strictures: acucise, cold-knife endoureterotomy and wall stents as a salvage approach

OBJECTIVE: To evaluate the factors influencing the results of endoureterotomy using cold-knife and cutting balloon dilatation, and permanent ureteral wall stents in patients with benign ureteral strictures after different operations affecting the ureter. MATERIALS AND METHODS: Over a 4-year period, in 18 patients, endoscopic cold-knife and Acucise endoureterotomies were performed in 13 and 7 renal units, respectively. Eight Memoterm permanent ureteral wall stents were inserted into 7 patients when endoureterotomy failed. Successful outcome was defined by the absence of re-stricture assessed both clinically and radiologically. RESULTS: The strictures were secondary to ureterolithotomy in 6, ureteroscopy in 3, gynecological procedures in 4, abdominal surgeries in 2, transplantation in 2 and continent urinary diversion in 1. The right and left ureters were unilaterally affected in 5 and 11 patients, respectively (5 of them had a solitary kidney), while the remaining 2 patients had bilateral ureteral strictures. We achieved total ureteral patency of 3 (43%) and 7 (54%) renal units with Acucise and cold-knife incision, respectively. Obstructive uropathy was resolved in 6 renal units (75%) of 8 using ureteral wall stents. CONCLUSION: Endoureterotomy with cold-knife or Acucise cutting balloon dilatation is effective in the treatment of iatrogenic ureteral strictures, but only in a selected group. Based on our results, the favorable prognostic criteria for endoureterotomy are the length (< or =1.5 cm), the nonischemic nature of the stricture and adequate renal function. As a salvage approach, permanent self-expanding ureteral wall stents with a 75% success rate may provide a satisfactory outcome for decompression of an obstructed system.     

Endourologic management of malignant ureteral strictures

PURPOSE: This retrospective analysis assessed the efficacy of balloon dilatation, endoureterotomy, percutaneous ureteroneocystostomy with stenting, and insertion of Wallstents in the management of malignant ureteral strictures with an intact or compromised vascular supply. PATIENTS AND METHODS: A series of 127 patients with ureteral strictures secondary to malignancies were assessed after at least 2-year follow-up (range 2-5 years; mean 3.5 years). Balloon dilation (antegrade approach) was applied in 46 patients, endoureterotomy with temporary stenting in 37, percutaneous ureteroneocystostomy with stenting in 34, bougie and stents in 13, and Wallstents in 31. RESULTS: Balloon dilatation was successful in only two of four malignant midureteral stenoses with intact vascular supplies and was even less successful (10%) in midureteral strictures with a compromised vascular supply. Endoureterotomy failed in all cases to prevent ureteral obstruction. Percutaneous ureteroneocystostomy achieved patency in 11 of 34 patients (33%) having a compromised ureteral vascular supply. Wallstents were successful in 18 of 31 patients (58%) with stenoses of the pelvic ureter. CONCLUSIONS: Percutaneous ureteroneocystostomy with stenting meets the requirement for palliation in patients with obstruction secondary to pelvic neoplasms. Wallstents proved to be most successful when used in the pelvic ureter.     

Endoscopic treatment of benign ureteral strictures

BACKGROUND: The traditional choice of procedure for treatment of ureteral stricture is open surgical repair. Advances in endourology have provided the urological surgeon with an alternative to open surgery for the treatment of benign ureteral stricture. METHODS: Twenty-seven benign ureteral strictures in 24 patients were treated by the endourological method. Twelve endoureterotomies were performed using a cold knife via a 9.5Fr Storz ureteroscope and 15 high pressure balloon dilations were performed. The ureters were stented with 7 Fr double-J stents for 6 weeks. RESULTS: The success rate was 9/12 (75%) in the endoureterotomy group and 9/15 (60%) in the balloon dilation group after follow-up for more than 6 months. CONCLUSIONS: Endoscopic treatment of ureteral strictures appeared to be a safe and reasonably effective modality for the treatment of ureteral strictures, especially for the short type that are non-ischaemic in origin and not associated with radiation therapy. Endourological treatment of ureteral strictures is the procedure of choice for initial management of benign ureteral strictures and has high success rates and fewer complications.     

微创经皮肾穿刺造瘘术治疗上尿路疾病

目的　探讨微创经皮肾穿刺造瘘术 (PCN)治疗上尿路疾病的可行性。　方法　肾结石90 6例 ,输尿管上段结石 132例 ,肾盂 输尿管连接处 (UPJ)狭窄 87例 ,移植肾结石 2例 ,马蹄肾结石 7例 ,放疗后双侧输尿管狭窄 19例 ,孤立肾结石 2 8例 ,肾结石合并肾囊肿 2例 ,肾脓肿 4 1例 ,利用微创PCN技术治疗。　结果　肾结石取净率 93% (84 2 /90 6 ) ;输尿管上段结石一期 1次取净率 10 0 % (132 /132 ) ;UPJ狭窄平均随诊 7个月 ,成功率 89% (77/87) ;2例移植肾结石和 7例马蹄肾结石均一次取净 ;放疗后输尿管狭窄治疗成功率 89% (17/19) ;孤立肾肾结石 1次取净率 86 % (2 4 /2 8) ;治疗肾结石合并肾囊肿 2例 ,术后随访 6个月囊肿无复发 ;治疗肾脓肿成功率 90 % (37/41)。　结论　微创PCN具有创伤小、出血少的优点 ,扩大了PCN治疗泌尿系疾病的范围 ,疗效良好。     

Long-term results of antegrade endoureterotomy using the holmium laser in patients with ureterointestinal strictures

Objectives. To investigate the effectiveness and morbidity of percutaneous laser endoureterotomy in the management of ureterointestinal anastomotic strictures after radical cystectomy and urinary diversion.Methods. Between May 1997 and August 2000, 19 percutaneous endoureterotomy incisions, including 3 repeated incisions, were performed on 15 patients with a mean age of 61 years (range 41 to 80) to treat ureterointestinal strictures. A total of 16 renal units were treated (9 left, 7 right), including one bilateral procedure. All procedures were performed using a 200-μm holmium laser fiber in antegrade fashion with a 7.5F flexible ureteroscope. A nephroureteral stent was left in place for 4 to 6 weeks postoperatively. Success was defined as radiologic improvement and/or the ability to return to full activity in the absence of flank pain, infection, or the need for ureteral stents or nephrostomy tubes.Results. With a median follow-up of 20.5 months (range 9 to 41), the overall success rate was 57% (8 of 14 renal units). Two patients were lost to follow-up. The mean operative time was 91 minutes, and no perioperative complications occurred. Three patients required repeated endoureterotomies, with two requiring open reimplantation. Overall, the endoureterotomy failed in 6 patients in the series, with five of the six failures involving left-sided strictures.Conclusions. Percutaneous endoureterotomy is an effective, minimally invasive treatment option for patients with ureterointestinal strictures after urinary diversion. Better visualization and a more precise incision may make the holmium laser a safer cutting modality than alternative methods in patients with ureteroenteric strictures. Patients with left-sided ureterointestinal strictures should be cautioned that endourologic management might have a lower success rate.     

输尿管镜联合钬激光治疗输尿管上段结石:附205例报告

目的 探讨输尿管镜联合钬激光治疗输尿管上段结石的效果和安全性.方法 回顾性分析205例输尿管上段结石患者行输尿管硬镜钬激光碎石治疗的临床资料,其中男91例,女114例,结石位于单侧188例,双侧17例,炎性息肉引起输尿管腔明显狭窄者12例.结石长径0.8～1.4 cm.结果 192例一次性碎石成功,单次碎石成功率为93.7%(192/205).9例有较大结石碎片(4～6 mm)残留于肾或输尿管内,4例在碎石过程中结石冲入肾内,其中1例较大结石(1.4 cm)移位至肾盂后改行PCNL,其余3例留置双J管改行ESWL,均治愈.19例合并炎性息肉同期行激光烧灼.手术时间15~90min,平均30 min.住院时间2~9 d,平均3.5 d.198例患者在门诊获得随访,随访时间3～24个月,平均6个月,结石均排尽.结论 输尿管镜联合钬激光治疗输尿管上段结石的一种比较理想的腔内碎石技术,其碎石成功率高,并发症发生率低,创伤小,患者术后恢复快,而且可同期处理结石合并炎性息肉和狭窄.     

Treatment of uretero-intestinal and ureterovesical strictures by Acucise balloon catheter

OBJECTIVE: Acucise balloon catheter has been proposed as an alternative to open surgery for the treatment of strictures of the ureteropelvic junction because of its low morbidity and the short hospital stay following the endoscopic procedure. The objective of this study was to evaluate the results of this technique applied to patients developing strictures after surgical reimplantation of the ureterovesical (UV) or uretero-intestinal (UI) junction. MATERIAL AND METHODS: Between March 1997 and January 2000, 12 strictures (11 patients) were treated by Acucise balloon catheter via an antegrade and/or retrograde approach with double J stenting for an average of 6 weeks (range: 4-12 weeks): six uretero-ileal strictures (three Bricker, one uretero-ileoplasty, one enterocystoplasty and one Kock pouch) and six ureterovesical strictures (Lich-Grégoir or Paquin UV reimplantations after gynaecological, vascular or endoscopic surgery). The median postoperative follow-up was 16 months (range: 10-36 months). A good result was defined by the absence of recurrence of the stricture evaluated both clinically and radiologically (regression of stasis measured by IVU and/or ultrasonography). RESULTS: The mean operating time was 70 minutes and the mean hospital stay was 4.8 days (range: 3-14 days). Only one intraoperative complication was observed (migration of the double J stent to the kidney). The operation was successful in eight patients (75%). The success rate was 83% for ureterovesical strictures and 50% for uretero-ileal strictures. A history of previous irradiation appeared to be a factor of failure. CONCLUSION: The Acucise procedure is a minimally invasive and effective (75% success rate) treatment option for the treatment of postoperative stricture after ureteric reimplantations. In our department, this option is considered to be first-line treatment, as surgical reimplantation is reserved for failures of the endoscopic technique.     

输尿管结石ESWL失败改腔内钬激光碎石术的疗效观察

目的 探讨输尿管结石ESWL失败后采用腔内钬激光碎石术的临床疗效。方法 自2001年10月至2002年8月，对28例输尿管结石(ESWL失败)行输尿管镜下钬激光碎石术。结果 26例经输尿管镜下钬激光碎石术治愈，治愈率92．8％(26／28)；1例结石上移，辅以ESWL治愈；1例因输尿管纤维性扭曲改开放手术。结论 输尿管镜下钬激光碎石术安全、有效、方便，可以作为输尿管结石的首选治疗。     

Modified extravesical ureteral reimplantation and routine stenting in kidney transplantation

In the past, extravesical ureteroneocystostomy has been technically modified several times, with varying results. In this study, we evaluate our experience with modified extravesical re-implantation and routine stenting. From January 1988 to September 2001, 411 consecutive renal transplantations (220 LRD/LUD, 191 CAD) were performed at our institutions. Of 220 kidneys utilized for living related transplantation, 39 were retrieved laparoscopically and 181 were retrieved by open nephrectomy. The ureteroneocystostomy performed was a modified Lich-Gregoir re-implantation with routine stenting, using the upper transplant ureter. A double ureter was encountered in 11 patients and was managed with a conjoint ureteral ostium-to-mucosa anastomosis, using two stents. In two patients with graft ureteropelvic junction (UPJ) stenosis, a double ipsilateral drainage was performed, applying modified extravesical reimplantation with concomitant ureteroneocystostomy. There were no ureteral leaks. Five (1.22%) patients developed temporary ureterovesical junction (UVJ) obstruction/edema following stent removal, which necessitated re-stenting for 4-6 weeks. Two patients (0.49%) developed delayed stenosis and were successfully treated with retrograde balloon dilatation.(One at the UPJ of a pediatric kidney, and one at UVJ). All patients with functioning grafts in this series are currently stent-free. We conclude that the modified extravesical reimplantation with routine stenting is an effective and safe technique in renal transplantation, associated with almost no complications.     

Holmium: Yttrium-Aluminum-Garnet Laser Endoureterotomy for Benign Ureteral Strictures: a Single-Centre Experience

Purpose: This study aimed to report the results of endoureterotomy for benign ureteral strictures using the holmium: yttrium-aluminum-garnet laser.

Material and methods: Nineteen patients (8 men and 11 women, mean age 51.47 years) underwent holmium: yttrium-aluminum-garnet laser endoureterotomy for benign ureteral strictures (8 proximal, 3 middle, and 8 distal) using semirigid ureteroscopy and 360-μm fibre at 1.2 J/pulse and 10 Hz. After completion of the incision, a 7-Fr double-J ureteral stent was left for 6 weeks. Thereafter, the patients were followed-up by ultrasound and/or intravenous urography at 36 monthly intervals.

Results: Success was defined as the absence of symptoms plus radiographic resolution of obstructions as assessed by diuretic renography and/or intravenous urography. With a mean follow-up of 40.2 months, success was achieved in 10 (52.6%) of the 19 patients. Nine patients developed recurrent strictures and were considered treatment failures. The stricture length and severity of hydronephrosis correlated with successful outcome, but gender, aetiology, side and location of strictures did not predict outcome.

Conclusions: Although endoureterotomy using a holmium: yttrium-aluminum-garnet laser has an equivocal outcome, the procedure is recommended as a safe, less invasive therapeutic option for the initial management of benign ureteral strictures.     

Ureteric obstruction in renal transplants: the role of percutaneous balloon dilatation.

With widespread use of balloon dilatation catheters outside the vascular system, percutaneous balloon dilatation has become an accepted alternative to surgery. Seventeen patients who developed ureteric stenosis following renal transplantation underwent 21 transrenal angioplastic balloon dilatations. Fifteen patients had lower ureteric strictures (2-22 mm long), and two had multiple strictures. The time interval between transplantation and obstruction ranged from 11 to 1370 days (median 71, mean 228.9 days). Nine patients were treated successfully (53%) with no stricture recurrence during the follow-up period, which ranged from 3 to 44 months (median 16, mean 17.8 months). In eight of nine patients in this group, the stricture impression on the inflation balloon was eliminated, and this appears to correlate best with a successful outcome. The eight patients who failed balloon dilatation and restenosed, did so within 7-42 days in seven patients; one patient had late stricturing at 238 days. Serious complications occurred in only one patient, who developed an A-V fistula not amenable to correction and necessitating transplant nephrectomy.