Correction of Ureteropelvic Junction Obstruction in Children: National Trends and Comparative Effectiveness in Operative Outcomes

Abstract

Purpose:

To assess the national trends and comparative effectiveness of the various treatments for pediatric ureteropelvic junction obstruction (UPJO).

Patients and Methods:

Within the Nationwide Inpatient Sample, a weighted estimate of 35,275 pediatric patients (<19 years; 1998–2010) with UPJO underwent open pyeloplasty (OP), laparoscopic pyeloplasty (LP), robot-assisted pyeloplasty (RP, ≥October 2008) or endopyelotomy (EP). National trends in utilization and comparative effectiveness were evaluated.

Results:

Minimally invasive pyeloplasty (RP+LP, MIP) utilization began to increase in 2007; MIP accounted for 16.9% of cases (2008–2010). EP accounted for 1.4% of all cases from 1998 to 2010. On individual multivariate models (relative to OP): (a) no significant differences were noted between groups for intraoperative complications; (b) RP and LP had equivalent risks of postoperative complications developing (vs OP), but EP had a significantly higher risk of postoperative complications; (c) RP and EP had significantly higher risks of necessitating transfusions; (d) RP, LP, and EP had higher overall risks of greater hospital charges; (e) RP had a lower risk of greater length of stay, while EP had a higher risk (LP and OP were equivalent).

Conclusions:

OP continues to be the predominant treatment for patients with UPJO. RP was the most common MIP modality in every age group. Compared with OP patients, RP patients had equivalent risk for intraoperative and postoperative complications, lower risk for greater length-of-stay, but higher risks for transfusions and greater hospital charges. LP patients had higher overall hospital charges, but no mitigating benefits relative to OP. EP fared poorly on most outcomes.

Introduction

Anderson-Hynes open pyeloplasty (OP)¹ has traditionally been the gold standard for the treatment of patients with ureteropelvic junction obstruction (UPJO). While OP has demonstrated success rates of >90% in children, numerous minimally invasive treatments have gained popularity. This is particularly true of adults, where a dramatic increase in laparoscopic and (in particular) robot-assisted pyeloplasty has occurred; these techniques represented a significant majority of all pyeloplasties (55.3%) for the first time in 2009.² While equivalent success rates^3,4 are reported for minimally invasive pyeloplasty (MIP) and OP in pediatric patients, primary endopyelotomy (EP) has lower operative success rates than pyeloplasty.⁵

In a recent study on trends in pediatric pyeloplasty, Monn and associates⁶ reported increasing rates for minimally invasive procedures, especially in older children. More importantly, because the long-term MIP success rates have been reported to be equivalent to OP, comparative effectiveness differences of these newer treatments in terms of actual operative morbidity, cost, and length of stay will likely drive treatment adoption and reimbursement over the next decade.

The purpose of the current study was to evaluate contemporary comparative effectiveness outcomes of the different modalities of UPJO correction in terms of operative morbidity and cost in a large national pediatric patient population.

Patients and Methods

Data source

Nationwide Inpatient Sample (NIS) is one of a large constellation of databases developed for the Healthcare Cost and Utilization Project. The NIS is the largest publicly accessible all payer inpatient database in the United States and accrues information from approximately 8 million hospital stays annually.⁷

Study population

Patients <19 years who underwent UPJO correction (International Classification of Diseases, 9th ed, Clinical Modification [ICD-9-CM] 55.87) between 1998 and 2010 were examined. Sampling weights were used to obtain national estimates. MIP patients were recognized based on procedure codes for robot assistance (ICD-9-CM 17.4x) and laparoscopic exploration (ICD-9-CM 54.21). The robotic code was introduced in October 2008; hence, all analyses involving RP (including all comparative effectiveness analyses) are based on patients who were treated after October 1, 2008 (n=6112). EP patients were identified based on concurrent procedure codes: Pyelotomy (ICD-9-CM 55.11) or ureteroscopy (ICD-9-CM 56.31), in conjunction with the ICD-9-CM 55.87. All other patients were classified as having OP. The occurrence of any intraoperative or postoperative complication was captured using modifications of previous methodology (Appendix).^8
–10

Patient and hospital-level characteristics

Age categories were as follows: Infants (<1), preschool (2–5), grade school (6–9), preadolescent (10–13), and adolescent (14–18). The Charlson Comorbidity Index (CCI) was calculated according to the Charlson and colleagues¹¹ classification, as modified by Deyo and coworkers.¹² We relied on median household income of the patient's ZIP code of residence, derived from the US Census, and the resulting data were divided into quartiles: <$25,000, $25,000–$34,999, $35,000–$44,999, and ≥$45,000. The rates of concurrent stent placement were also assessed. Hospital characteristics evaluated included annual hospital volume, teaching status, hospital region, and hospital location. The annual hospital volume was divided into quartiles for each procedure. Hospital region and hospital teaching status were obtained as described previously.²

Statistical analysis

The chi-square test was used for categorical comparisons. Individual binary logistic regression models were used to evaluate predictors of intraoperative and postoperative complications, homologous blood transfusions, greater length of stay (≥75th percentile), and greater hospital charges (≥75th percentile of total hospital charges after adjustment for inflation). Analyses were conducted using the R statistical package (the R foundation for Statistical Computing, version 2.15.2). Statistical significance was set at a P=value of 0.05.

Results

National trends in utilization

A weighted estimate of 35,275 pediatric patients (<19 years) with UPJO underwent OP, laparoscopic pyeloplasty (LP), robot-assisted pyeloplasty (RP), or EP between 1998 and 2010 (Fig. 1). OP, MIP, and EP represented 93.7%, 5%, and 1.4% of all procedures. A substantial rise in MIP utilization was noted beginning in 2007 (Fig. 2), mostly driven by RP. The rates of RP and LP in 2008 (last quarter only), 2009, and 2010 were RP: 4.6%, 12.6%, 11%, and LP: 4.2%, 5.4%, 4%, respectively. With the proliferation of RP, the national rates for OP dipped in 2009 below 80% for the first time. In contrast, after initial increases, LP rates have remained relatively stable in the 3% to 5% range since 2003. EP rates remained stable at 1% to 2% over the entire study, with no substantial upward trend noted at any point during the study period.

FIG. 1.

Trends in the total number of cases of ureteropelvic junction obstruction correction in the United States (1998–2010; n=35,275)

FIG. 2.

Trends in correction of ureteropelvic junction obstruction in the United States (1998–2010): proportion of patients undergoing open pyeloplasty, minimally invasive pyeloplasty and endopyelotomy.

Baseline characteristics

Younger patients were more likely to undergo OP (infants 96.5%) whereas older patients showed a higher rate of RP (adolescents 35.1%), LP (preadolescents 9.2%), and EP (preadolescents 4.3%, P<0.001). Female patients were more likely to undergo EP (66.7%) and less likely to be treated with OP (25.2%, P<0.001). Moreover, Caucasian patients were more likely to undergo OP (56.6%) and RP (57.7%), whereas African American patients were mostly treated with LP (7.7%) and Hispanic patients with LP (23.4%) and EP (23.1%, P<0.001). Patients with a higher comorbidity profile (CCI ≥1, 8.1%), who were treated at urban (100%) and nonteaching hospitals (29.5%, all P<0.001) were more likely to undergo EP. Furthermore, patients who resided in areas with the highest ZIP code income were more likely to undergo LP (36%, P<0.001). Finally, patients who came from the western part of the United States were more likely to be treated with RP (42.3%, P<0.001). All baseline characteristics are shown in Table 1.

Table 1.

Weighted Descriptive Characteristics of 6113 Patients <19 Years Old Undergoing Correction of Ureteropelvic Junction Obstruction, Nationwide Inpatient Sample, 10/2008–2010

Variables	Overall (%)	OP (%)	RP (%)	LP (%)	EP (%)	P
Weighted number	6113 (100)	4977 (81.4)	758 (12.4)	272 (4.5)	106 (1.7)	—
			% per row
Age (years)						<0.001
Infants (<1)	100	96.5	2.1	0.8	0.6
Preschool (2–5)	100	82.9	11.0	5.3	0.8
Grade school (6–9)	100	73.8	17.8	6.7	1.7
Preadolescent (10–13)	100	72.1	14.4	9.2	4.3
Adolescent (14–18)	100	52.5	35.1	8.2	4.2
			% per column
Sex						<0.001
Male	72.6	74.8	67	64.3	33.3
Female	27.4	25.2	33	35.7	66.7
Race						<0.001
Caucasian	56.2	56.6	57.7	48.7	48.1
African American	6	6	5.5	7.7	4.8
Hispanic	17.4	17.5	14	23.4	23.1
Other	10.4	11	5.2	13.2	9.6
Unknown	9.9	8.8	17.6	7	14.4
CCI						<0.001
0	95.4	96.2	93	92.6	81.9
1	4.1	3.4	6.3	5.5	18.1
2	0.3	0.2	0	1.8	0
≥3	0.2	0.2	0.7	0	0
Insurance status						<0.001
Private	56	53.4	70	59.6	66.7
Medicaid	38.5	40.9	26.8	29.4	28.6
Medicare	0.1	0	0.7	0	0
Other	5.5	5.6	2.5	11	4.8
Median household income						<0.001
1st quartile	19.2	19.6	18	16.5	14.3
2nd quartile	22.9	23.4	18.8	24.6	28.6
3rd quartile	29.7	29.2	35.5	21	33.3
4th quartile	26.1	25.4	27.7	36	23.8
Hospital location						0.007
Rural	4	4.1	5.3	1.5	0
Urban	96	95.9	94.7	98.5	100
Hospital region						<0.001
Northeast	15.4	15.3	17.7	12.1	14.3
Midwest	18.9	17.9	25.3	15.8	28.6
South	29.6	31.6	14.7	35.7	22.9
West	36.1	35.2	42.3	36.4	34.3
Academic status						<0.001
Nonteaching	13.7	11.6	25.9	12.5	29.5
Teaching	86.3	88.4	74.1	87.5	70.5

OP=open pyeloplasty; RP=robot-assisted pyeloplasty; LP=laparoscopic pyeloplasty; EP=endopyelotomy; CCI=Charlson Comorbidity Index.

Comparative effectiveness of perioperative outcomes

Tables 2 and 3 show the univariable and multivariable results of the comparative effectiveness assessment of perioperative outcomes, respectively. First, no patient died from any of the procedures used for the correction of UPJO. Patients who were treated with EP were more likely to experience overall complications (18.1% compared with OP with 9.1%, RP with 11.2%, and 11.1% with LP, P<0.001). Moreover, patients who underwent EP were more likely to experience respiratory (8.6%, P<0.001) and genitourinary (9.5%, P<0.001) complications, as well as to receive blood transfusions (4.8, P<0.001), whereas RP patients were more likely to experience wound complications (1.2%, P<0.001). Mean length of stay for OP, RP, LP, and EP were 2.5, 1.9, 2.7, and 3.1 days, respectively (median 2 days for each procedure).

Table 2.

Weighted Operative Outcomes of 6113 Patients <19 Years Old Undergoing Correction of Ureteropelvic Junction Obstruction, Nationwide Inpatient Sample, 2008 (Last Quarter)–2010

Variables	Overall (%)	OP (%)	RP (%)	LP (%)	EP (%)	P
In-hospital mortality	–	–	–	–	–	–
Intraoperative complications	0.5	0.5	0.8	–	–	0.351
Postoperative complications
Overall	9.6	9.1	11.2	11.1	18.1	0.004
Cardiac	0.1	0.1	–	–	–	0.767
Respiratory	1	1	–	–	8.6	<0.001
Genitourinary	6.0	5.4	8.6	9.2	9.5	<0.001
Gastrointestinal	1.7	1.6	2.1	1.8	–	0.437
Wound	0.3	0.2	1.2	–	–	<0.001
Vascular	0.1	0.1	–	–	–	0.767
Infectious	0.2	0.3	–	–	–	0.330
Miscellaneous	1.3	1.3	1.2	1.8	–	0.554
Homologous transfusion	0.6	0.4	1.2	–	4.8	<0.001
Greater length of stay^a	26	27.1	14.7	27.9	46.7	<0.001
Greater hospital charges^a	25	20.0	47.9	36.1	62.9	<0.001

≥75th percentile.

OP=open pyeloplasty; RP=robot-assisted pyeloplasty; LP=laparoscopic pyeloplasty; EP=endopyelotomy.

Table 3.

Multivariable Risks for Operative Outcomes in 6113 Patients <19 Years Old Undergoing Correction of Ureteropelvic Junction Obstruction, 2008 (Last Quarter)–2010

		RP			LP			EP
Outcome^a	OP	OR	95% CI	P	OR	95% CI	P	OR	95% CI	P
In-hospital mortality	–	–	–	–	–	–	–	–	–	–
Intraoperative complications	Ref	0.690	0.22–2.21	0.533	–	–	0.993	–	–	0.996
Postoperative complications	Ref	0.906	0.68–1.20	0.494	0.962	0.63–1.46	0.858	1.961	1.15–3.36	0.014
Homologous transfusion	Ref	11.99	2.66–54.10	0.001	–	–	0.994	44.82	4.92–408.5	0.001
Greater length of stay^b	Ref	0.423	0.34–0.53	<0.001	0.832	0.62–1.11	0.214	2.125	1.40–3.22	<0.001
Greater hospital charges^b	Ref	2.436	1.99–2.97	<0.001	1.652	1.23–2.23	0.001	4.859	3.03–7.78	<0.001

Individual multivariable models were generated for each outcome, but only the results for operative technique (OP, RP, LP, EP) are shown here. Variables in each model: Operative technique, age, sex, race, insurance status, Charlson Comorbidity Index, median household income quartiles, year of surgery, hospital region, location, academic status, and hospital volume quartiles.

≥75th percentile.

OP=open pyeloplasty; RP=robot-assisted pyeloplasty; LP=laparoscopic pyeloplasty; EP=endopyelotomy; OR=odds ratio; CI=confidence interval; Ref=Referent.

With regard to intraoperative complications, there was no difference between the treatment groups on univariable or multivariable analyses. On multivariable analysis, RP and LP patients were at no higher risk to have a postoperative complication (vs OP). Patients undergoing EP were at a significantly higher risk of experiencing a postoperative complication (vs OP, odds ratio [OR]: 1.961, 95% confidence interval [CI]: 1.15–3.36; P=0.014). Patients undergoing RP (vs OP; OR: 11.997, 95% CI: 2.66–54.09; P=0.001) and EP (vs OP; OR: 44.819, 95% CI: 4.92–408.54, P=0.001) were more likely to need a blood transfusion. LP patients were not at a significantly higher or lower risk for a blood transfusion compared with OP patients.

Mean and median total hospital charges (adjusted for inflation) for OP, RP, LP, and EP were: $31, 282 and $25,735; $39,745 and $35,966; $45,524 and $33,002; $40,118 and $37,165, respectively. The rates of concurrent stent placement were 45.8%, 61.8%, 46.3%, and 71.7%, respectively, for OP, RP, LP, and EP (P<0.001). On multivariable analysis (including adjustment for rates of concurrent stent placement), RP (vs OP; OR: 2.436, 95% CI: 1.99–2.97; P<0.001), LP (vs OP; OR: 1.652, 95% CI: 1.23–2.23; P=0.001), and EP (vs OP; OR: 4.859, 95% CI: 3.03–7.78; P<0.001) each incurred a higher risk for greater hospital charges.

On multivariable analysis, RP patients had a significantly lower risk for greater length of stay relative to OP patients (vs OP; OR: 0.423, 95% CI: 0.34–0.53, P<0.001); in contrast, EP patients (vs OP; OR: 2.125, 95% CI: 1.40–3.22; P<0.001) were at a higher risk for greater length of stay. LP patients did not have a significantly lower risk of greater length of stay relative to OP patients.

Discussion

Large studies informing the comparative effectiveness debate on UPJO correction and its trends are rare. In a seminal report on pediatric pyeloplasty trends, Nelson and colleagues¹³ identified important variations in treatment patterns between 1988 and 2000: The rates of early intervention were decreasing with more newborns undergoing observation. Differences in timing of surgery were also noted between Caucasian and non-Caucasian patients, with a higher proportion of the latter undergoing surgery in the first 6 months of life. Evaluating the Pediatric Health Information Database in another pivotal study, Vemulakonda and associates¹⁴ reported that LP utilization increased with time until 2003, and that LP is associated with higher charges with equivalent length of stay. Using the same dataset, Tanaka and coworkers¹⁵ reported that LP was associated with shorter hospital stay and less narcotic use in patients >10 years (vs OP).

In spite of these reports, no study has reported national trends in OP, RP, LP, and EP utilization or undertaken a comprehensive comparative effectiveness analysis of the morbidity and costs of these treatments. In an era when OP is becoming “minimally invasive” with smaller incisions¹⁶ and stent-less techniques,¹⁷ and the novel treatments do not have higher operative success rates, comparative effectiveness assessments of operative morbidity and cost become paramount.

Our study has a number of novel findings. While OP remains the predominant treatment modality for UPJO, a substantial increase in MIP utilization has been observed after 2007, mostly driven by RP. LP rates have remained stable since 2003, and EP rates remained stable throughout the study period. RP was the most common MIP modality in every single age group and has superseded LP at the national level.

We also report comprehensive comparative effectiveness outcomes for the each of the treatments. Relative to OP patients, RP patients had equivalent risk for intraoperative and postoperative complications, lower risk for greater length of stay, but higher risks for transfusions and greater hospital charges. Usually, robotic surgery is associated with a lower likelihood of blood transfusion compared with the open approach.¹⁸

Nevertheless, despite the favorable association of the robotic approach with the necessity of blood transfusions in other fields, the opposite seems to be true for RP. This might be caused by the very narrow operation site, especially in children, which could prolong the learning curve for this robotic intervention. Moreover, it is likely that most of the robotic cases were performed by surgeons in their learning phase, which could explain the relatively high transfusion rate in RP patients. Alternatively, it may reflect increased caution on the surgeon's part during adoption of the new technique of LP/RP. In addition, patients treated with RP or LP were more likely to have comorbidities relative to OP patients, which may put these patients at risk for bleeding or possibly lower their threshold for transfusion.

Given the higher rates of concurrent stent placement in patients undergoing RP, LP, and EP and the probable need for a second procedure to remove the stents in a significant number of these patients (resulting in additional charges after the index admission that are not recorded in the current study), the rates of greater charges might indeed be higher with these treatments. Consistent with previous studies, LP patients had higher overall hospital charges,¹⁴ with no other significant benefits relative to OP (particularly length of stay).^14,19

Kim and associates⁵ have shown that EP has lower long-term operative success rates than pyeloplasty. The current report is the first to show that EP also performs the poorest in terms of comparative effectiveness of perioperative outcomes: EP conferred higher risks of postoperative complications, transfusions, greater length of stay, and greater hospital charges.

Apart from the traditional drawbacks of using administrative databases (retrospective nature, miscoding, underreporting, and inadequate risk-stratification), the lack of information regarding disease-level factors (e.g., anomalous vessels, location of constriction), subclassification of the procedure type (e.g., dismembered vs flap pyeloplasty), and operative indications (e.g., primary vs redo procedure), represent the major limitations of the present study within which our findings should be viewed. Moreover, the code for robot-assisted surgery was introduced in October 2008 and could have been underreported once it was introduced (lack of knowledge of the specific coding, insurance-related), at least in the initial phase.

In the absence of a widely used risk-stratification scheme for evaluating pediatric comorbidities, we opted to use CCI in our study. While this is not uncommon in the assessment of pediatric surgical outcomes,²⁰ patients <19 years were not the target population in the initial development of CCI. The NIS also lacks follow-up information after the index admission, and this is another limitation, because readmissions and additional procedures are not accounted for in our study. Furthermore, to achieve comparability between studies, researchers analyzing claims-based datasets should use established coding systems in future projects on pyeloplasty.

Conclusions

While OP remains the predominant treatment for patients with UPJO, a substantial increase in MIP utilization has been noticed after 2007, mostly driven by RP. RP was the most common MIP modality in every age group and has superseded LP at the national level. Compared with OP patients, RP patients had equivalent risk for intraoperative and postoperative complications, lower-risk for greater length of stay, but higher risks for transfusions and greater hospital charges. LP patients had higher overall hospital charges, but no other mitigating benefits relative to OP. EP fared poorly on almost every outcome.

Disclosure Statement

Quoc-Dien Trinh is a consultant for Intuitive Surgical.

Footnotes

Abbreviations Used

Appendix 1.

List of ICD-9-CM Codes Used

Variable	Codes
Intraoperative complications	41511, 4582, 45821, 45829, 5121, 9982, 9991, 900, 901, 902, 903, 904
Postoperative complications
Cardiac	40201, 40211, 40291, 410, 411, 4275, 4278, 9971, 4294
Respiratory	466, 480, 481, 482, 483, 485, 486, 5070, 514, 5184, 5185, 51881, 7991, 9973
Vascular	4151, 41511, 430, 431, 433, 434, 435, 436, 4442, 4448, 451, 453, 4599, 9972, 9977, 9992
Wound	567, 5688, 5967, 6088, 9981, 9983, 99832, 9986, 99813, 99851
Genitourinary	590, 5933, 595, 597, 604, 7882, 9963, 9975
Gastrointestinal	5311, 5312, 5321, 5322, 5323, 5401, 558, 560, 7876, 9974, 5651, 5692, 5693, 5695, 5696, 5793, 00845
Neurologic	9970, 99700, 99701, 99702, 99709, 436, 951, 952, 953, 954, 955, 956, 3446, 3530, 354, 355, 7234
Infectious	53641, 51901, 9985, 9993, 038, 0545, 7907, 99591, 99592
Miscellaneous	0418, 2768, 4589, 584, 7823, 7824, 7855, 9950, 9954, 9994, 9996, 9997, 9984, 9987, 9988, 9989, 53640, 53642, 53649, 5793, 99586
Transfusions	9902, 9904

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