Quantifying the Additional Difficulty of Pediatric Robot-Assisted Laparoscopic Re-Do Pyeloplasty: A Comparison of Primary and Re-Do Procedures

Abstract

Background:

Re-do pyeloplasty after failed open or laparoscopic ureteropelvic junction (UPJ) obstruction correction can be a challenging procedure because of scar formation at the previous anastomosis site and decreased vascularity of the ureter. This study compared the perioperative parameters for pediatric robot-assisted laparoscopic (RAL) primary and re-do pyeloplasties with an emphasis on the intra-operative parameters.

Materials and Methods:

We compared the perioperative parameters of pediatric RAL procedures performed by a single surgeon at a tertiary care children's hospital for both primary ureteropelvic junction obstruction (UPJO) and recurrent UPJO after a previous open or laparoscopic procedure over 2013–2015. The operative time was subdivided as total operative time, console time, port placement time, dissection time to UPJ, and anastomosis time.

Results:

A total of 65 pediatric RAL pyeloplasty procedures for UPJO were performed (55 primary and 10 re-do pyeloplasties) during the study period. The console times were 43.3% longer for re-do pyeloplasties than for primary pyeloplasties (133.0 ± 30.7 versus 92.8 ± 24.0 minutes, respectively, P < .01). The re-do cases had longer operative times, especially for UPJ exposure (52.2 ± 21.0 versus 28.0 ± 14.0 minutes, P < .01). There were no conversions to open surgery or significant perioperative complications. There was no difference in hospital pain medication usage and hospital length of stay between the 2 groups. The treatment success rates were 98.2% (54/55) and 100% (10/10), respectively.

Conclusions:

RAL re-do pyeloplasty is associated with significantly longer operative times as compared with primary pyeloplasties, especially during the exposure of the UPJ, but it is overall a safe and effective surgical modality for persistent/recurrent UPJO in children. As surgeons are increasingly asked for more accurate predictions of operative time lengths when scheduling cases, this information can be helpful for surgeons when scheduling these cases and with counseling families.

Introduction

Persistent or recurrent ureteropelvic junction obstruction (UPJO) is reported to have an incidence of 3%–6% after open or laparoscopic pyeloplasty in the pediatric population.^1,2 Re-operation for persistent/recurrent UPJO can be a challenging procedure because of scar formation at the previous anastomosis site and decreased vascularity of the ureter.

Robot-assisted laparoscopic (RAL) procedures using the da Vinci system (Intuitive Surgical, Inc., Sunnyvale, CA) provide a minimally invasive option for many reconstructive procedures in children. In particular, robotic surgery is particularly suited for pediatric re-do pyeloplasty, which has several demanding procedural steps that can be challenging with conventional laparoscopy. There have been previous reports of robotic pediatric re-do pyeloplasties using the da Vinci robot system, but none described a comparison of RAL re-do pyeloplasty with a control group.^3–6

Therefore, we investigated the efficacy and safety of RAL re-do pyeloplasty by comparing the perioperative surgical outcomes with those of RAL primary pyeloplasty with an emphasis on intra-operative parameters.

Patients and Methods

We retrospectively reviewed and compared the perioperative parameters of pediatric primary and re-do RAL pyeloplasties performed by a single surgeon over a 2-year period (September 2013 to October 2015). Patient demographics, operative times, intra- and postoperative complications, hospital pain medication usage, hospital length of stay, and treatment success rates were included in the analysis. Patients were excluded from the analysis if the peri- or postoperative data were incomplete.

For preoperative imaging studies, we performed renal ultrasounds in all patients and diuretic renal scans in most patients if indicated. These imaging studies, along with history and physical exam, were used to determine surgical indications. Indications for pediatric pyeloplasty were worsening of hydronephrosis, obvious anatomic obstruction on diuretic renal scan, renal function deterioration, recurrent flank pain, or acute pyelonephritis related to UPJO.

A single surgeon performed all the operations. At the time of surgery, retrograde pyelography was often performed to delineate the ureteral anatomy and the length of the stricture segment. Port placement was via a conventional multiport approach.⁷ The surgical procedure steps that we used have been previously described.^8,9 An 8.5-mm camera port and two 5-mm robotic ports were used, as well as an optional 5-mm accessory laparoscopic port in the contralateral upper quadrant.

Left-sided primary RAL cases were usually performed via a transmesenteric approach. However, if the transmesenteric approach was not possible due to a thickened mesentery or non-visualization of the dilated renal pelvis through the mesentery, a retrocolic approach was used. Right-sided primary RAL cases were performed via a retrocolic approach. All RAL re-do pyeloplasties in this series were performed via a retrocolic approach. Double J stents were used in all primary and re-do pyeloplasty cases, and the stents were removed via cystoscopy at the 1-month mark. Patients were followed with renal ultrasounds at 1, 3–6, 12, and 24 months postoperatively.

Definitions and outcome measurements

The indications for the operation were categorized as worsening hydronephrosis, symptoms related to UPJO including flank/abdominal pain, or acute pyelonephritis. The operative times were recorded as the total operative time (from skin incision until wound closure), console time, port placement time, dissection time to ureteropelvic junction (UPJ), and anastomosis time. Postoperative complications were categorized according to the Clavien grading system.¹⁰ Hospital pain medication usage was calculated as morphine sulfate equivalents (mg/kg). Treatment success was defined as an improvement of hydronephrosis on postoperative ultrasounds, symptom relief, or improvement of drainage on MAG-3 renal scan.

Statistical analysis

Statistical analyses were performed with SPSS for Windows version 21.0 (IBM Corporation, Armonk, NY). Descriptive statistics are expressed as mean ± standard deviation. A Mann-Whitney U test was used to compare the operative times. P < .05 was considered statistically significant.

Ethics statement

This study was approved by the local institutional review board (Protocol H-33575). As a retrospective review, written informed consent was exempted for all study participants.

Results

A total of 65 pediatric RAL procedures for UPJO were performed during the study period, including 55 primary pyeloplasties and 10 re-do pyeloplasties. Of the 10 persistent/recurrent UPJO cases, 8 were referred cases in which the initial pyeloplasties were performed at other institutions, and the remaining 2 cases underwent initial open pyeloplasty at our institution.

There were no statistical differences between the primary and re-do pyeloplasty groups in terms of patient age, gender, laterality, preoperative hydronephrosis grade, and indication for surgery (Table 1). The total operative times were 31.1% longer for the re-do pyeloplasty cases (187.7 ± 28.5 minutes for re-do cases versus 143.2 ± 25.4 minutes for primary cases, P < .01), and the console times were 43.3% longer for re-do cases as well (133.0 ± 30.7 versus 92.8 ± 24.0 minutes, respectively, P < .01). There were longer segmental operative times for the re-do cases, especially for the exposure of the UPJ, which was 86.4% longer for re-do cases than primary cases (52.2 ± 21.0 versus 28.0 ± 14.0 minutes, respectively, P < .01). There were no conversions to open surgery or significant perioperative complications.

Table 1.

Patient Demographics

	Primary (n = 55)	Re-do (n = 10)	P
Age at surgery (years)	5.1 ± 5.1	8.2 ± 7.2	.11
Gender, n (%)			.24
Male	40 (72.7)	9 (90.0)
Female	15 (27.3)	1 (10.0)
Laterality, n (%)			.92
Right	23 (41.8)	4 (40.0)
Left	32 (58.2)	6 (60.0)
Preoperative HN grade (SFU grade), n (%)			.56
Grade III	33 (60.0)	5 (50.0)
Grade IV	22 (40.0)	5 (50.0)
Indication for operation, n (%)			.48
Worsening HN	32 (58.2)	7 (70.0)
Symptoms related to UPJO	23 (41.8)	3 (30.0)

HN, hydronephrosis; SFU, Society of Fetal Urology; UPJO, ureteropelvic junction obstruction.

Postoperative complications occurred in 3 patients: 2 experienced a postoperative urinary tract infection (Clavien grade II), and the remaining patient experienced postoperative ileus without the need for additional pharmacological treatment (Clavien grade I). There was no difference in hospital pain medication usage, hospital length of stay, and postoperative double J catheter duration between the 2 groups. The treatment success rates were 98.2% (54/55) and 100% (10/10), respectively (Table 2). In addition, low hospital pain medication usage and short hospital lengths of stay were noted for both the primary pyeloplasty group and the re-do pyeloplasty group (Table 2).

Table 2.

Operative and Postoperative Parameters

	Primary (n = 55)	Re-do (n = 10)	P
Operative time (minutes)
Operative time (excluding cystoscopy and RGP)	143.2 ± 25.4	187.7 ± 28.5	<.01
Console time	92.8 ± 24.0	133.0 ± 30.7	<.01
Port placement time	20.2 ± 5.1	23.6 ± 7.7	.08
Dissection time to UPJ	28.0 ± 14.0	52.2 ± 21.0	<.01
Anastomosis time	44.8 ± 16.2	55.1 ± 23.0	.09
Intraoperative complication, n (%)	0	1 (9.1)^a	.02
Conversion to open pyeloplasty	0	0	1
Postoperative complication, n (%)	2 (3.6)^b	1 (10.0)^c	.38
Postoperative narcotics (morphine equivalents, mg/kg)
Oral	0.36 ± 0.32	0.26 ± 0.19	.36
Intravenous	0.05 ± 0.08	0.02 ± 0.03	.20
Overall	0.41 ± 0.36	0.28 ± 0.19	.27
Postoperative intravenous ketololac (mg/kg)	0.60 ± 0.85	0.78 ± 0.87	.55
Hospital length of stay (hours)	34.6 ± 12.0	29.6 ± 3.1	.20
Postoperative DJ stent duration (days)	33.5 ± 7.6	36.3 ± 6.4	.28
Postoperative follow-up (months)	10.5 ± 7.8	13.6 ± 5.6	.23
Treatment success, %	98.2 (54/55)	100 (10/10)	.67

Inferior epigastric vessel injury during port placement.

One urinary tract infection and 1 ileus.

Urinary tract infection.

DJ, double J; RGP, retrograde pyelography; UPJ, ureteropelvic junction.

The patient characteristics and the operative times of the re-do operations are shown in Table 3. A 15-year-old male patient (patient No. 7) underwent staged bilateral pyeloplasties because of worsening bilateral hydronephrosis, so a total of 10 re-operations were performed in 9 patients. The mean age of the patients at the time of the re-operations was 8.2 ± 7.2 (range 0.5–17.3) years. Initial pyeloplasties were performed via open pyeloplasty in nine renal units and via laparoscopic pyeloplasty for one renal unit. Interventions before RAL re-do pyeloplasty that included balloon dilation, percutaneous nephrostomy, or double J catheter insertion were performed in five renal units. The time between the initial and re-do operations varied from 0.2 to 14.8 years.

Table 3.

Patient Characteristics and Operative Time of Re-Do Pyeloplasties

							Operative time (minutes)
No. of patients	Age (years)	Gender	Laterality	Initial operation and post-pyeloplasty interventions	Time from initial operation (years)	Indication	Total	Console	From console start to UPJ exposure	Anasto-mosis
1	0.5	M	Right	Open+PCN	0.2	Worsening HN	169	118	56	43
2	0.6	F	Right	Open+PCN+DJ	0.4	Worsening HN	224	167	48	82
3	1.2	M	Left	Open	0.6	Worsening HN	231	188	82	71
4	1.5	M	Left	Open+balloon dilation+PCN	0.6	Worsening HN	201	134	45	41
5	5.7	M	Right	Open	0.5	Worsening HN	146	78	23	49
6	8.4	M	Left	Open	14.8	Flank pain	156	111	47	49
7	15.0	M	Right	Open+several interventions	>10	Worsening HN	197	138	84	36
	15.6		Left	Open+several interventions	>10	Worsening HN	218	146	40	66
8	16.6	M	Left	Laparoscopic	7	Flank pain	171	114	70	19
9	17.3	M	Left	Open	5	Flank pain	174	136	27	95

DJ, double J; HN, hydronephrosis; PCN, percutaneous nephrostomy; UPJ, ureteropelvic junction.

When the 10 re-do pyeloplasties were divided into 2 groups according to the presence of a post-pyeloplasty intervention after the primary surgery (patients No. 1, 2, 4, and 7 versus patients No. 3, 5, 6, 8 and 9) and compared with respect to the operative time, the mean console time of the patients who underwent post-pyeloplasty intervention was longer than that of patients without post-pyeloplasty interventions but the difference was not statistically significant (140.6 ± 17.9 versus 125.4 ± 40.7 minutes, respectively, P = .47). When patients were divided into two different age groups (infants and toddlers <2 years old versus children 5 years and older and adolescents), the mean console time for the infants and toddlers was longer than the mean console time for the children and the adolescents, but this difference was not statistically significant (151.8 ± 31.6 versus 120.5 ± 25.0 minutes, respectively, P = .12).

Discussion

The incidence of persistent or recurrent UPJO is reported to be 3%–6% after primary pyeloplasty in the pediatric population.^1,2 Re-do pyeloplasty after open or laparoscopic UPJO correction can be a challenging procedure because of scar formation at the previous anastomosis site and decreased vascularity of the ureter.

The use of RAL pyeloplasty has expanded in recent years, and pyeloplasty has been reported as the most common RAL procedure in children.¹¹ Because of its minimal invasive nature as well as its efficacy that is comparable to open pyeloplasty, RAL pyeloplasty is a viable alternative to open surgery for the treatment of UPJO in children.^12–14 Several reports of RAL re-do pyeloplasty for persistent/recurrent UPJO have demonstrated a high success rate and a low complication rate.^3–6,15

This is the first article to directly compare the perioperative parameters for pediatric RAL primary and re-do pyeloplasties, where specific attention was placed on the operative times as a surrogate marker for complexity of the procedure, as more difficult surgeries are often associated with longer operative times. Although longer operating room times are often assumed for re-do cases, our study is one of the first to demonstrate that the operative times from console start to UPJ exposure were significantly longer in the re-do pyeloplasty group than in the primary pyeloplasty group.

Since the time from skin incision to console start as well as the anastomosis time was similar between the 2 groups, there appeared to be no difference in difficulty of trocar placement, robot docking, and anastomosis for RAL re-do pyeloplasty as compared with RAL primary pyeloplasty. As with open re-do pyeloplasty, the most challenging step during RAL re-do pyeloplasty was dissecting the ureter and renal pelvis from the scar tissue that formed after the previous failed primary pyeloplasty.

Our study results provide evidence that longer operative times are associated with re-do pyeloplasties, as little evidence that supports this is available in the literature, although it is a widespread assumption. We used objective and quantified parameters of subdivided operative times, and our results confirm that the most challenging surgical step in RAL re-do pyeloplasties is related to the dissection around UPJ rather than port placement or anastomosis. We believe that these results will provide better information to surgeons who are performing RAL re-do pyeloplasties, especially as they discuss the procedure with families before surgery.

Although a trans-mesenteric RAL approach is possible for many pediatric left-sided cases, all of the RAL re-do pyeloplasties in our series were performed via a retrocolic approach. Since a trans-mesenteric approach often allows for a small surgical window and may limit a wide dissection of the UPJ area, we prefer the retrocolic approach for the re-do cases. We did not experience any intraoperative complications related with dissection around the UPJ, or any conversions to open surgery.

Of note, the peri- and postoperative parameters, hospital pain medication usage, and the hospital stay length did not differ between the primary and the re-do pyeloplasty group. The success rates were 98.2% and 100%, respectively. These results demonstrate that both RAL primary pyeloplasty and RAL re-do pyeloplasty are safe and effective surgical options in the pediatric population. In previous reports, the complication rate after open re-do pyeloplasty was reported to be as high as 80%, hospital pain medication usage was 7.18 mg/kg morphine equivalents, the mean hospital stay length was 4.6 days, and the success rate was 83%–100%. Our experience with RAL re-do pyeloplasties demonstrated higher success rates, less hospital pain medication usage, and shorter hospital stays as compared with historical controls of open re-do pyeloplasty.

For the 10 re-do cases, there were no differences in operative time between patients with or without post-pyeloplasty intervention before re-do surgery. Although the failure of both pyeloplasty and post-pyeloplasty intervention can lead to difficulty with dissection around the UPJ area, the operative times were similar between the 2 groups in our series, implying that the RAL procedure can be safely performed even in patients who experienced failed pyeloplasty and failed post-pyeloplasty interventions. In addition, the mean operative time was noted to be longer in the younger age group (infants and toddlers <2 years old) than in the older age group (children 5 years and older and adolescents), although this difference was not statistically significant. RAL re-do pyeloplasty may potentially be more difficult in younger children due to a limited working space or smaller caliber of the ureter.

The limitation of this study is mostly due to the retrospective design and small case volume of re-do pyeloplasty patients. As a result, it is difficult to compare the relative difficulty of redo pyeloplasty after open primary pyeloplasty with laparoscopic primary pyeloplasty. However, RAL re-do pyeloplasty after an open pyeloplasty may be associated with a reduced need for extensive dissection through scar tissue since the transmesenteric approach of the RAL re-do pyeloplasty involves the dissection of virgin tissue except at the level of the UPJ.

Another factor that can affect the study results is trainee involvement in these cases, similar to most academic tertiary care institutions. However, trainee involvement is usually widespread among academic teaching institutions, and we assumed that the effects were distributed among all patients.

Recording the segmental operative times of the RAL pyeloplasty and re-do pyeloplasty procedures allowed us to use these times as a surrogate for the difficulty of each step. Further, in the United States, where coding modifiers as the 22-modifier of Current Procedural Terminology (CPT^®; American Medical Association) can be used for the billing of difficult procedures, this analysis can provide evidence to payers that operative times are, indeed, significantly longer for re-do pyeloplasties when compared with primary pyeloplasties.

Until now, several modalities have been applied for the surgical treatment of persistent/recurrent UPJO in the pediatric population (Table 4). Open re-do pyeloplasty has traditionally been the standard surgical treatment option with a high success rate.^16–18 However, it requires a larger surgical incision, a longer hospital stay, and significant hospital pain medication usage when compared with minimally invasive surgical modalities, such as endopyelotomy and laparoscopic re-do pyeloplasty with or without robot assistance. Endopyelotomy has been reported to have a variable success rate of 39%–94%,^17,19–21 which does not seem suitable for the treatment of pediatric patients who need long-term successful solutions. Several reports of the laparoscopic approach without robot assistance for failed UPJO cases in adults have shown high success rates.^22–25 However, only a few reports of laparoscopic re-do pyeloplasty in pediatric populations exist, and mostly in adolescents.^16,17,24,25

Table 4.

Review of the Literature of Surgical Outcomes for Recurrent Ureteropelvic Junction Obstruction in the Pediatric Population (18-Year-Olds or Younger)

							Complication according to Clavien grade system
Authors	Year	Treatment option	No. of renal units	Mean age in years (range)	Mean operative time (minutes)	Mean length of stay (days)	I	II	III	IV	Hospital pain medication usage (mg/kg morphine equivalent)	Conversion to open surgery	Success rate (%)
Piaggio et al.¹⁶	2007	ORP	5	13.3 (8.7–15.5)	203	4.6	1	2	1	0	7.18	NA	83
		LRP	6	7.5 (1.3–18)	253	2.5	0	0	0	0	0.46	0	80
Braga et al.¹⁷	2007	ORP+LRP	14^a	7.2 (1–17)	NA	2.0	0	0	0	0	NA	0	100
		EP	18	6 (2–14)	NA	1.3	0	0	1	0	NA	0	39
Veenboer et al.¹⁹	2011	EP	11	6.8 (0.1–15.3)	69	2.8	1	0	0	0	NA	0	64
Kim et al.²⁰	2012	EP	31	6.5 (0.25–16)	165	3	2	1	0	0	NA	0	94
Parente et al.²¹	2015	EP	9	5.8 (0.3–3.2)	61	3.8	1	1	1	0	NA	0	78
Hemal et al.³	2008	RLRP	6	13.3 (10–16)	106	3.4	1	0	0	0	NA	0	100
Lindgren et al.⁴	2012	RLRP	16^b	5.6 (1.2–15.3)	303	1.6	1	2	0	0	0.2	1	88
Asensio et al.⁵	2015	RLRP	5	13.8 (8–18)	144	2.6	0	0	0	0	NA	0	100
Powell et al.²⁴	2015	LRP	5	3.8 (1.1–9.3)	190	1.4	0	0	0	0	NA	0	100
Davis et al.⁶	2016	RLRP	23	4.0 (1.2–19)	198	2.3	0	6	0	0	NA	0	78
Moscardi et al.²⁵	2017	LRP	11^c	6.9 (2.0–16.0)	205	4	NA	NA	0	0	NA	0	90
Current study	—	RLRP	10	8.2 (0.5–17.3)	188	1.0	0	1	0	0	0.41	0	100

Ten open re-do pyeloplasties, 2 open UCs, and 2 laparoscopic re-do pyeloplasties.

Thirteen RAL re-do pyeloplasties and 3 RAL UCs.

Eight laparoscopic re-do pyeloplasties and 3 laparoscopic UCs.

EP, endopyelotomy; LRP, laparoscopic re-do pyeloplasty; ORP, open re-do pyeloplasty; RAL, robot-assisted laparoscopic; RLRP, robot-assisted laparoscopic re-do pyeloplasty; UC, ureterocalycostomy.

Robot-assisted laparoscopy has advantages over conventional laparoscopy due to the technical benefits during several demanding procedural steps of pediatric re-do pyeloplasty, including dissection of the scarred tissue around the UPJ, ureteric spatulation, and uretero-pelvic anastomosis within the small anatomical working space of children. Since Passerotti et al. first reported on pediatric RAL re-do pyeloplasty in 2007,¹⁵ several articles about the experiences with RAL procedures for failed pyeloplasties in children have reported a high success rate with its minimal invasive nature.

Hemal et al. reported the surgical outcomes of 9 re-do pyeloplasties, with 6 of the 9 children between the ages of 10 and 16 years.³ Complications associated with the operation were minimal, the mean hospital stay length was 3.4 days, and postoperative imaging studies showed hydronephrosis improvement in all 9 patients. Lindgren et al. reported their experience of 15 RAL re-do pyeloplasties and 1 RAL ureterocalycostomy in children aged 1.1–15.4 years with an 88% success rate.⁴ Asensio et al. reported performing 153 pediatric pyeloplasties over a 14-year period, with 9 of them (6%) being re-do pyeloplasties. Five of the 9 total re-do pyeloplasties were performed with RAL procedures, and the success rate was 100%.⁵ Davis et al. reported their experience of re-do RAL pyeloplasties over an 8-year period from two institutes. Of the total 23 children who underwent re-do RAL pyeloplasty, 18 patients >12 months of follow-up were analyzed for success; 13 demonstrated improved (76%), 3 unchanged (18%), and 1 worse hydronephrosis (6%).⁶

Our current study includes 10 RAL re-do pyeloplasties over a 2-year period. All have shown improvement in the hydronephrosis. Of note, compared with previous reports of RAL re-do pyeloplasties, our study population included several infants and toddlers. Four children were <2 years old, including 2 infants who were 6 and 8 months of age, respectively. The relatively large number of successful procedures in children <2 years old indicates that RAL re-do pyeloplasty can be safely performed in small children, including infants.

Based on our experience and a review of the literature, RAL re-operative repair for failed pyeloplasty is a safe and highly effective treatment option. Similar to how RAL primary pyeloplasty is being suggested as the new standard surgical treatment option,^13,14 RAL re-do pyeloplasty may eventually replace the traditionally open surgical standard as well.

However, one should be careful before directly applying our study results to general clinical practice. All the operations were performed by an experienced pediatric robotic surgeon with a decade of pediatric urological robotic surgery experience. A recent study suggested that a novice surgeon should perform more than 30–40 cases to overcome the learning curve in RAL pyeloplasty.²⁶ Our study results can be especially helpful for surgeons who have overcome this learning curve and are planning to perform challenging cases of re-do pyeloplasty.

Conclusions

RAL re-do pyeloplasties are associated with significantly longer operative times as compared with RAL primary pyeloplasties, especially during the exposure of the UPJ. No significant differences in other perioperative surgical outcomes between RAL re-do and RAL primary pyeloplasties were noted. This can be helpful for surgeons when scheduling for these cases and for family counseling.

Footnotes

Disclosure Statement

This project was supported by a grant from the Auxiliary to Texas Children's Hospital Denton Cooley Innovation Award. C.J.K. is a consultant and course director for Intuitive Surgical, Inc. All other authors have no competing financial interests.

References

Helmy

, Sarhan

, Hafez

, Elsherbiny

, Dawaba

, Ghali

. Surgical management of failed pyeloplasty in children: Single-center experience. J Pediatr Urol, 2009; 5:87–89.

Romao

, Koyle

, Pippi Salle

, Alotay

, Figueroa

, Lorenzo

, Bagli

, Farhat

. Failed pyeloplasty in children: Revisiting the unknown. Urology, 2013; 82:1145–1147.

Hemal

, Mishra

, Mukharjee

, Suryavanshi

. Robot assisted laparoscopic pyeloplasty in patients of ureteropelvic junction obstruction with previously failed open surgical repair. Int J Urol, 2008; 15:744–746.

Lindgren

, Hagerty

, Meyer

, Cheng

. Robot-assisted laparoscopic reoperative repair for failed pyeloplasty in children: A safe and highly effective treatment option. J Urol, 2012; 188:932–937.

Asensio

, Gander

, Royo

, Lloret

. Failed pyeloplasty in children: Is robot-assisted laparoscopic reoperative repair feasible?. J Pediatr Urol, 2015; 11:69.e61–e66.

Davis

, Burns

, Corbett

, Peters

. Reoperative robotic pyeloplasty in children. J Pediatr Urol, 2016; 12:394.e1–e7.

Chandrasoma

, Kokorowski

, Peters

, Koh

. Straight-arm positioning and port placement for pediatric robotic-asisted laparoscopic renal surgery. J Robotic Surg, 2010; 4:29–32.

Peters

. Pediatric robot-assisted pyeloplasty. J Endourol, 2011; 25:179–185.

Kokorowski

, Chandrasoma

, De Filippo

, Chang

, Peters

, Koh

. Pediatric robot-assisted laparoscopic pyeloplasty using a transmesenteric approach. J Endourol Part B Videourol, 2010; 24. DOI: 10.1089/vid.2010.0044.

10.

Dindo

, Demartines

, Clavien

. Classification of surgical complications: A new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg, 2004; 240:205–213.

11.

Cundy

, Shetty

, Clark

, Chang

, Sriskandarajah

, Gattas

, Najmaldin

, Yang

, Darzi

. The first decade of robotic surgery in children. J Pediatr Surg, 2013; 48:858–865.

12.

Barbosa

, Kowal

, Onal

, Gouveia

, Walters

, Newcomer

, Chow

, Nguyen

. Comparative evaluation of the resolution of hydronephrosis in children who underwent open and robotic-assisted laparoscopic pyeloplasty. J Pediatr Urol, 2013; 9:199–205.

13.

Sukumar

, Roghmann

, Sood

, Abdo

, Menon

, Sammon

, Sun

, Varda

, Trinh

, Elder

. Correction of ureteropelvic junction obstruction in children: National trends and comparative effectiveness in operative outcomes. J Endourol, 2014; 28:592–598.

14.

Cundy

, Harling

, Hughes-Hallett

, Mayer

, Najmaldin

, Athanasiou

, Yang

, Darzi

. Meta-analysis of robot-assisted vs conventional laparoscopic and open pyeloplasty in children. BJU Int, 2014; 114:582–594.

15.

Passerotti

, Nguyen

, Eisner

, Lee

, Peters

. Laparoscopic reoperative pediatric pyeloplasty with robotic assistance. J Endourol, 2007; 21:1137–1140.

16.

Piaggio

, Noh

, Gonzalez

. Reoperative laparoscopic pyeloplasty in children: Comparison with open surgery. J Urol, 2007; 177:1878–1882.

17.

Braga

, Lorenzo

, Skeldon

, Dave

, Bagli

, Khoury

, Pippi Salle

, Farhat

. Failed pyeloplasty in children: Comparative analysis of retrograde endopyelotomy versus redo pyeloplasty. J Urol, 2007; 178:2571–2575; discussion 2575.

18.

Chung

, Hong

, Im

, Lee

, Kim

, Han

. Delayed redo pyeloplasty fails to recover lost renal function after failed pyeloplasty: Early sonographic changes that correlate with a loss of differential renal function. Korean J Urol, 2015; 56:157–163.

19.

Veenboer

, Chrzan

, Dik

, Klijn

, de Jong

. Secondary endoscopic pyelotomy in children with failed pyeloplasty. Urology, 2011; 77:1450–1454.

20.

Kim

, Tanagho

, Traxel

, Austin

, Figenshau

, Coplen

. Endopyelotomy for pediatric ureteropelvic junction obstruction: A review of our 25-year experience. J Urol, 2012; 188:1628–1633.

21.

Parente

, Angulo

, Burgos

, Romero

, Rivas

, Ortiz

. Percutaneous endopyelotomy over high pressure balloon for recurrent ureteropelvic junction obstruction in children. J Urol, 2015; 194:184–189.

22.

Levin

, Herrell

. Salvage laparoscopic pyelo plasty in the worst case scenario: After both failed open repair and endoscopic salvage. J Endourol, 2006; 20:808–812.

23.

Basiri

, Behjati

, Zand

, Moghaddam

. Laparoscopic pyeloplasty in secondary ureteropelvic junction obstruction after failed open surgery. J Endourol, 2007; 21:1045–1051; discussion 1051.

24.

Powell

, Gatti

, Juang

, Murphy

. Laparoscopic pyeloplasty for ureteropelvic junction obstruction following open pyeloplasty in children. J Laparoendosc Adv Surg Tech A, 2015; 25:858–863.

25.

Moscardi

, Barbosa

, Andrade

, Mello

, Cezarino

, Oliveira

, Srougi

, Dénes

, Lopes

. Reoperative laparoscopic ureteropelvic junction obstruction repair in children: Safety and efficacy of the technique. J Urol, 2017; 197:798–804.

26.

Tasian

, Wiebe

, Casale

. Learning curve of robotic assisted pyeloplasty for pediatric urology fellows. J Urol, 2013; 190:1622–1626.