Interactive network-based clustering and investigation of multimorbidity association matrices with associationSubgraphs.

MOTIVATION: Making sense of networked multivariate association patterns is vitally important to many areas of high-dimensional analysis. Unfortunately, as the data-space dimensions grow, the number of association pairs increases in O(n2); this means that traditional visualizations such as heatmaps quickly become too complicated to parse effectively. RESULTS: Here, we present associationSubgraphs: a new interactive visualization method to quickly and intuitively explore high-dimensional association datasets using network percolation and clustering. The goal is to provide an efficient investigation of association subgraphs, each containing a subset of variables with stronger and more frequent associations among themselves than the remaining variables outside the subset, by showing the entire clustering dynamics and providing subgraphs under all possible cutoff values at once. Particularly, we apply associationSubgraphs to a phenome-wide multimorbidity association matrix generated from an electronic health record and provide an online, interactive demonstration for exploring multimorbidity subgraphs. AVAILABILITY AND IMPLEMENTATION: An R package implementing both the algorithm and visualization components of associationSubgraphs is available at https://github.com/tbilab/associationsubgraphs. Online documentation is available at https://prod.tbilab.org/associationsubgraphs_info/. A demo using a multimorbidity association matrix is available at https://prod.tbilab.org/associationsubgraphs-example/.

Prospective Multicenter Evaluation of Pain Before and After Removal of Nonobstructing Renal Calculi: A CoRE Initiative.

PURPOSE: Flank pain associated with stone disease is typically caused by a stone that obstructs urine flow. However, it is plausible that nonobstructing kidney stones may still cause pain. We performed a multicenter, observational trial to evaluate whether treatment of small nonobstructing calyceal stones improves pain and kidney stone-specific health-related quality of life. MATERIALS AND METHODS: Patients aged 18 years or older with nonobstructing renal stone(s) up to 10 mm in longest diameter and moderate to severe pain were recruited. All participants completed 3 questionnaires: the Brief Pain Inventory (BPI), the Patient-Reported Outcomes Measurement Information System pain interference form 6a, and the Wisconsin Stone Quality of Life questionnaire. Thereafter, all participants underwent ureteroscopy for renal stone treatment. All 3 questionnaires were repeated at 2, 6 to 8, and at 12 weeks postprocedure. The primary outcomes were change in preoperative to 12-week postoperative mean BPI score and worst BPI pain score. RESULTS: A total of 43 patients with nonobstructing kidney stones and associated flank pain were recruited. All stones were removed. Preoperatively, BPI scores for mean pain and worst pain were 5.5 and 7.2, respectively which decreased to 1.8 and 2.8 respectively at 12 weeks postoperatively. Wisconsin Stone Quality of Life questionnaire mean score increased from 70.4 to 115.3 at 12 weeks postoperatively. A total of 86% and 69% of patients had at least a 20% and 50% reduction in their mean pain scores, respectively. CONCLUSIONS: This study determined that patients benefit significantly from the removal of calyceal nonobstructing kidney stones for at least 12 weeks with a reduction in pain and an increase in quality of life. Therefore, surgical removal of these stones in this patient population should be offered as a treatment option.

Real-World Effectiveness of Preventive Pharmacological Therapy in Patients With Urolithiasis: A Retrospective Cohort Study.

RATIONALE & OBJECTIVE: Data supporting the efficacy of preventive pharmacological therapy (PPT) to reduce urolithiasis recurrence are based on clinical trials with composite outcomes that incorporate imaging findings and have uncertain clinical significance. This study evaluated whether the use of PPT leads to fewer symptomatic stone events. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: Medicare enrollees with urolithiasis who completed 24-hour urine collections that revealed hypercalciuria, hypocitraturia, low urine pH, or hyperuricosuria. EXPOSURE: PPT (thiazide diuretics for hypercalciuria, alkali for hypocitraturia or low urine pH, or uric acid lowering drugs for hyperuricosuria) categorized as (1) adherent to guideline-concordant PPT, (2) nonadherent to guideline-concordant PPT, or (3) untreated. OUTCOME: Symptomatic stone event occurrence (emergency department [ED] visit or hospitalization for urolithiasis or stone-directed surgery). ANALYTICAL APPROACH: Cox proportional hazards regression. RESULTS: Among 13,942 patients, 31.0% were prescribed PPT. Compared with no treatment, concordant/adherent PPT use was associated with a significantly lower hazard of symptomatic stone events for patients with hypercalciuria (HR, 0.736 [95% CI, 0.593-0.915]) and low urine pH (HR, 0.804 [95% CI, 0.650-0.996]) but not for patients with hypocitraturia or hyperuricosuria. These associations were largely driven by significantly lower rates of ED visits after initiating PPT among the concordant/adherent group versus untreated patients. Patients with hypercalciuria had adjusted 2-year predicted probabilities of a visit of 3.8% [95% CI, 2.5%-5.2%%] and 6.9% [95% CI, 6.0%-7.7%] for the concordant/adherent PPT and no-treatment groups, respectively. Among patients with low urine pH, these probabilities were 4.3% (95% CI, 2.9%-5.7%) and 7.3% (95% CI, 6.5%-8.0%) for the concordant/adherent PPT and no-treatment groups, respectively. LIMITATIONS: Potential bias from the possibility that patients prescribed PPT had more severe disease than untreated patients. CONCLUSIONS: Patients with urolithiasis and hypercalciuria who were adherent to treatment with thiazide diuretics as well as those with low urine pH adherent to prescribed alkali therapy had fewer symptomatic stone events than untreated patients. PLAIN-LANGUAGE SUMMARY: Despite multiple clinical trials demonstrating the efficacy of thiazide diuretics and alkali for secondary prevention of kidney stones, they are infrequently prescribed due in part to a lack of data about their effectiveness in real-world settings. We analyzed medical claims from older adults with kidney stones for whom urine chemistry data were available. We found that patients who took prescribed thiazide diuretics for elevated urine calcium levels or alkali for low urinary pH were less likely to experience symptomatic stone recurrences than untreated patients. This benefit was expressed as lower rates of emergency department visits after initiating therapy. Our findings should inform the prescription of and adherence to treatment with thiazide diuretics and alkali for the prevention of recurrent kidney stones.

The Uniform grading tooL for flexIble ureterorenoscoPes (TULIP-tool): a Delphi consensus project on standardised evaluation of flexible ureterorenoscopes.

OBJECTIVE: To develop a standardised tool to evaluate flexible ureterorenoscopes (fURS). MATERIALS AND METHODS: A three-stage consensus building approach based on the modified Delphi technique was performed under guidance of a steering group. First, scope- and user-related parameters used to evaluate fURS were identified through a systematic scoping review. Then, the main categories and subcategories were defined, and the expert panel was selected. Finally, a two-step modified Delphi consensus project was conducted to firstly obtain consensus on the relevance and exact definition of each (sub)category necessary to evaluate fURS, and secondly on the evaluation method (setting, used tools and unit of outcome) of those (sub)categories. Consensus was reached at a predefined threshold of 80% high agreement. RESULTS: The panel consisted of 30 experts in the field of endourology. The first step of the modified Delphi consensus project consisted of two questionnaires with a response rate of 97% (n = 29) for both. Consensus was reached for the relevance and definition of six main categories and 12 subcategories. The second step consisted of three questionnaires (response rate of 90%, 97% and 100%, respectively). Consensus was reached on the method of measurement for all (sub)categories. CONCLUSION: This modified Delphi consensus project reached consensus on a standardised grading tool for the evaluation of fURS - The Uniform grading tooL for flexIble ureterorenoscoPes (TULIP) tool. This is a first step in creating uniformity in this field of research to facilitate future comparison of outcomes of the functionality and handling of fURS.

Prospective randomized trial of 2 versus 12-weeks of postoperative antibiotics after percutaneous nephrolithotomy in complex patients with infection-related kidney stones.

PURPOSE: Treatment of struvite kidney stones requires complete surgical stone removal combined with antibiotic therapy to eliminate urinary tract infections and preventive measures to reduce stone recurrence. The optimal duration of antibiotic therapy is unknown. We sought to determine if 2- or 12-weeks of antibiotics post percutaneous nephrolithotomy (PNL) for infection stones resulted in better outcomes for stone recurrence and positive urine cultures. MATERIAL AND METHODS: This multi-center, prospective randomized trial evaluated patients with the clinical diagnosis of infection stones. Patients were randomized to 2- or 12-weeks of postoperative oral antibiotics (nitrofurantoin or culture-specific antibiotic) and included if residual fragments were ≤4 mm on computed tomography imaging after PNL. Imaging and urine analyses were performed at 3-, 6-, and 12-months post-procedure. RESULTS: Thirty-eight patients were enrolled and randomized to either 2-weeks (n = 20) or 12-weeks (n = 18) of antibiotic therapy post-PNL. Eleven patients were excluded due to residual fragments >4 mm, and 3 patients were lost to follow-up. The primary outcome was the stone-free rate (SFR) at 6 months post-PNL. At 3-, 6-, and 12-months follow-up, SFRs were 72.7% versus 80.0%, 70.0% versus 57.1%, 80.0% versus 57.1% (p = ns), between 2- and 12-week-groups, respectively. At 3-, 6-, and 12-months follow-up, positive urine cultures were 50.0% versus 37.5%, 50.0% versus 83.3%, and 37.5% versus 100% between 2- and 12-week groups, respectively (p = ns). CONCLUSIONS: For patients with stone removal following PNL, neither 2-weeks nor 12-weeks of postoperative oral antibiotics is superior to prevent stones and recurrent positive urine cultures.

A Randomized Controlled Trial of Preoperative Prophylactic Antibiotics for Percutaneous Nephrolithotomy in Moderate to High Infectious Risk Population: A Report from the EDGE Consortium.

PURPOSE: Postoperative infectious related complications are not uncommon after percutaneous nephrolithotomy. Previously, we noted that 7 days of antibiotics did not decrease sepsis rates compared to just perioperative antibiotics in a low risk percutaneous nephrolithotomy population. This study aimed to compare the same regimens in individuals at moderate to high risk for sepsis undergoing percutaneous nephrolithotomy. MATERIALS AND METHODS: Patients were prospectively randomized in this multi-institutional study to either 2 days or 7 days of preoperative antibiotics. Enrolled patients had stones requiring percutaneous nephrolithotomy and had either a positive preoperative urine culture or existing indwelling urinary drainage tube. Primary outcome was difference in sepsis rates between the groups. Secondary outcomes included rate of nonseptic bacteriuria, stone-free rate and length of stay. RESULTS: A total of 123 patients at 7 institutions were analyzed. There was no difference in sepsis rates between groups on univariate analysis. Similarly, there were no differences in nonseptic bacteriuria, stone-free rate and length of stay. On multivariate analysis, 2 days of antibiotics increased the risk of sepsis compared to 7 days of antibiotics (OR 3.1, 95% CI 1.1-8.9, p=0.031). Patients receiving antibiotics for 2 days had higher rates of staghorn calculus than the 7-day group (58% vs 32%, p=0.006) but post hoc subanalysis did not demonstrate increased sepsis in the staghorn only group. CONCLUSIONS: Giving 7 days of preoperative antibiotics vs 2 days decreases the risk of sepsis in moderate to high risk percutaneous nephrolithotomy patients. Future guidelines should consider infectious risk stratification for percutaneous nephrolithotomy antibiotic recommendations.

Recurrence- and progression-free survival in intermediate-risk non-muscle-invasive bladder cancer: the impact of conditional evaluation and subclassification.

OBJECTIVES: To assess the change in rates of recurrence-free survival (RFS) and progression-free survival (PFS) based on the duration of survival without recurrence or progression among patients with intermediate-risk (IR) non-muscle-invasive bladder cancer (NMIBC), and to examine the predictive factors for recurrence at different time points by assessing conditional RFS and PFS. PARTICIPANTS AND METHODS: A cohort of 602 patients treated with transurethral resection of bladder tumour and histopathologically diagnosed with IR NMIBC was included in this retrospective study. RESULTS: The conditional RFS rate at 1, 2, 3, 4 and 5 years improved with increased duration of RFS; however, the conditional PFS rate did not improve over time. Multivariable analyses showed that recurrent tumour, multiple tumours, tumour size (>3 cm), immediate postoperative instillation of chemotherapy, and administration of BCG were independent predictive factors for recurrence at baseline. The predictive ability of these factors disappeared with increasing recurrence-free survivorship. Subclassification of these patients with IR NMIBC into three groups using clinicopathological factors (recurrent tumour, multiple tumours, tumour size) demonstrated that the high IR group (two factors) had significantly worse RFS than the intermediate (one factor, P < 0.001) and low IR groups (no factor, P = 0.005) at baseline. This subclassification stratified conditional risk of RFS also at 1, 3 and 5 years, which provides the basis for distinct surveillance protocols among patients with IR NMIBC. CONCLUSION: Conditional survival analyses of patients with IR NMIBC demonstrate that RFS changes over time, while PFS does not change. These data support distinct surveillance protocols based on the subclassification of IR NMIBC.

Celiac plexus block for chronic flank pain: a case series.

Non-obstructive, chronic flank pain in urologic patients can be a challenging problem to manage. In this series, we examined the efficacy of celiac plexus blockade in providing pain relief and reducing opiate use in 14 adult urology patients with non-obstructive flank pain for > 1 year. Demographic, clinical, and procedural variables were collected from the medical record for retrospective analysis. Subjective improvement in pain occurred in 11 individuals (79%), and 5 (50%) were able to reduce their daily morphine equivalent dose (MED). Celiac plexus blockade is a viable option for symptomatic relief in urologic patients with non-obstructive chronic flank pain.

Urological In-Flight Medical Events on Commercial Airlines.

PURPOSE: In-flight medical events are rare but may cause significant distress as access to care is limited. There is a paucity of data on in-flight urological medical events. We describe urological in-flight medical emergencies and report clinical and flight outcomes. MATERIALS AND METHODS: We reviewed all in-flight urological medical emergencies between 2015 and 2017 from MedAire®, a ground based medical support center that provides remote medical advisory services to approximately 35% of commercial airline passenger traffic worldwide. Our primary end point was the incidence rates of in-flight urological medical events. We also characterized the types of in-flight medical emergencies, in-flight management and their impact on flight status. Statistical analyses included Student's t-tests, chi-square analysis and analysis of variance. RESULTS: We identified 1,368 (1%) urological in-flight medical emergencies from a total of 138,612 in-flight medical emergencies, with an incidence of 0.5 per million passengers. The most common in-flight medical emergencies were lower urinary tract symptoms (35%), urinary retention (30%) and flank pain (21%). Among in-flight medical emergencies 883 (60%) resolved in flight, 273 (28%) required on-arrival medical evaluation and 21 (1.5%) resulted in flight diversions. Of the flight diversions the majority were due to urinary retention (12, 57%) and less commonly flank pain (6, 28%) and testicular/abdominal pain (3, 15%). CONCLUSIONS: The most common causes of urological in-flight medical emergencies are lower urinary tract symptoms, urinary retention and renal colic, the majority of which resolved in flight. These data are useful for informing flight personnel and emergency kit equipment needs to minimize the impact of these events when they occur.

Linking 24-h urines to clinical phenotypes: what alternatives does the future bring?

PURPOSE OF REVIEW: The 24-h urine test is recommended as part of the metabolic evaluation for patients with nephrolithiasis to guide preventive interventions. However, this test may be challenging to interpret and has limits in its predictive ability. In this review, we summarize and discuss the most recent research on the opportunities and challenges for utilizing urinary biomarkers for kidney stone prevention. RECENT FINDINGS: Contemporary studies utilizing the 24-h urine test have improved our understanding of how to better administer testing and interpret test results. Beyond the standard panel of 24-h urine parameters, recent applications of proteomics and metabolomics have identified protein and metabolic profiles of stone formers. These profiles can be assayed in future studies as potential biomarkers for risk stratification and prediction. Broad collaborative efforts to create large datasets and biobanks from kidney stone formers will be invaluable for kidney stone research. SUMMARY: Recent advances in our understanding of kidney stone risk have opened opportunities to improve metabolic testing for kidney stone formers. These strategies do not appear to be mutually exclusive of 24-h urine testing but instead complementary in their approach. Finally, large clinical datasets hold promise to be leveraged to identify new avenues for stone prevention.

Postoperative Opiate Use in Urological Patients: A Quality Improvement Study Aimed at Improving Opiate Disposal Practices.

PURPOSE: We aimed to determine trends in postoperative opiate management among urological patients, identify associations with opiate keeping and foster appropriate opiate disposal after surgery via introduction of an educational handout. MATERIALS AND METHODS: We retrospectively analyzed opiate practices in 68 patients who had undergone urological surgery. In a separate consecutive cohort of 59 patients we distributed a handout detailing FDA (Food and Drug Administration) approved disposal methods. Patient opiate obtainment, use and disposal were assessed via telephone interviews with prescription filling data verified using the Tennessee CSMD (Controlled Substances Monitoring Database). Opiate keeping was defined as possessing any opiates more than 3 weeks after surgery or more than 4 times the duration of the postoperative prescription, whichever was longer. RESULTS: Opiate keeping was observed in 41 patients (72%) in our initial cohort. Of these patients 68% left the medication unsecured at home. Major barriers to opiate disposal included concern for return of disease specific pain in 44% of patients and unrelated pain in 29%. As assessed on a short test, opiate keepers were less knowledgeable about safe disposal practices compared to nonkeepers (72% vs 85%, p = 0.005). Among opiate keepers there was an improvement in knowledge scores after the intervention (66% to 77%, p = 0.03). When comparing pre-education to post-education, there was no detectable improvement in the rate of opiate keeping (72% vs 68%, p = 0.66) or proper disposal (9% vs 8%, p = 1.0). CONCLUSIONS: Opiate keeping is common following urological surgery and a major barrier to disposal is concern for the return of disease specific pain. Future interventions aimed at limiting opiate keeping should combine evidence-based prescription practices and targeted patient education.

Plant and Animal Protein Intake and Risk of Incident Kidney Stones: Results from the Shanghai Men's and Women's Health Studies.

PURPOSE: High animal protein intake is a risk factor for nephrolithiasis. Whether plant based sources of protein are associated with kidney stone risk is not well studied. We examined the association of animal and plant protein intake with the risk of incident kidney stones in Shanghai, China. MATERIALS AND METHODS: Dietary intakes were obtained from a validated food frequency questionnaire at baseline. Self-reported stone events were ascertained at baseline and at followup visits. Multivariable Cox regression models were used to evaluate the associations of protein intake with the incident stone risk. RESULTS: During 319,211 and 696,950 person-years of followup 1,451 men and 1,202 women, respectively, reported incident stones. The average ± SD intake of animal and plant protein standardized to 2,000 kcal was 31.3 ± 13.7 and 48.4 ± 7.2 gm per day in women, and 30.8 ± 13.3 and 51.3 ± 7.6 gm per day, respectively, in men. On multivariable analysis participants in the highest quintiles of animal and nondairy animal protein intake showed an increased risk of incident stones compared to those in the lowest quintiles (HR 1.16, 95% CI 1.01-1.32, p=0.03 vs HR 1.14, 95% CI 1.01-1.30, p=0.04). Compared to the lowest quintile the highest intake quintiles of the animal-to-plant protein ratios and the nondairy animal-to-plant protein ratios were positively associated with stone risk (HR 1.17, 95% CI 1.03-1.33, p=0.02 and HR 1.20, 95% CI 1.06-1.36, p=0.005, respectively). No association was observed with plant protein intake (ptrend=0.14). CONCLUSIONS: In this population with a relatively low animal protein intake and a high plant protein intake, a greater animal protein intake was associated with a kidney stone risk. Increasing the proportion of plant protein relative to animal protein appeared protective against the risk.

Green tea intake and risk of incident kidney stones: Prospective cohort studies in middle-aged and elderly Chinese individuals.

OBJECTIVES: To investigate the association between green tea intake and incident stones in two large prospective cohorts. METHODS: We examined self-reported incident kidney stone risk in the Shanghai Men's Health Study (n = 58 054; baseline age 40-74 years) and the Shanghai Women's Health Study (n = 69 166; baseline age 40-70 years). Information on the stone history and tea intake was collected by in-person surveys. Multivariable Cox proportional hazards models were adjusted for baseline demographic variables, medical history and dietary intakes including non-tea oxalate from a validated food frequency questionnaire. RESULTS: During 319 211 and 696 950 person-years of follow up, respectively, 1202 men and 1451 women reported incident stones. Approximately two-thirds of men and one-quarter of women were tea drinkers at baseline, of whom green tea was the primary type consumed (95% in men, 88% in women). Tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69-0.88; women: hazard ratio 0.8, 95% confidence interval 0.77-0.98) and specifically green tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69-0.88; women: hazard ratio 0.84, 95% confidence interval 0.74-0.95) had lower incident risk than never/former drinkers. Compared with never/former drinkers, a stronger dose-response trend was observed for the amount of dried tea leaf consumed/month by men (hazard ratiohighest category 0.67, 95% confidence interval 0.56-0.80, Ptrend  < 0.001) than by women (hazard ratiohighest category 0.87, 95% confidence interval 0.70-1.08, Ptrend  = 0.041). CONCLUSIONS: Green tea intake is associated with a lower risk of incident kidney stones, and the benefit is observed more strongly among men.

The Role of the 24-Hour Urine Collection in the Prevention of Kidney Stone Recurrence.

PURPOSE: Kidney stone prevention relies on the 24-hour urine collection to diagnose metabolic abnormalities and direct dietary and pharmacological therapy. While its use is guideline supported for high risk and interested patients, evidence that the test can accurately predict recurrence or treatment response is limited. We sought to critically reassess the role of the 24-hour urine collection in stone prevention. MATERIALS AND METHODS: In addition to a MEDLINE® search to identify controlled studies of dietary and pharmacological interventions, evidence supporting the AUA (American Urological Association) and EAU (European Association of Urology) guidelines for metabolic stone prevention were evaluated. Additionally, the placebo arms of these studies were examined to assess the stone clinic effect, that is the impact of regular office visits without specific treatment on stone recurrence. RESULTS: The 24-hour urine test has several limitations, including the complexity of interpretation, the need for repeat collections, the inability to predict stone recurrence with individual parameters and supersaturation values, the unclear rationale of laboratory cutoff values and the difficulty of determining collection adequacy. Only 1 prospective trial has compared selective dietary recommendations based on 24-hour urine collection results vs general dietary instructions. While the trial supported the intervention arm, significant limitations to the study were found. Placebo arms of intervention trials have noted a 0% to 61% decrease in stone recurrence rate and a remission rate during the study of 20% to 86%. CONCLUSIONS: Whether all recurrent stone formers benefit from 24-hour urine collection has not been established. Additional comparative effectiveness trials are needed to determine which stone former benefits from selective therapy, as guided by the 24-hour urine collection.

The origins of urinary stone disease: upstream mineral formations initiate downstream Randall's plaque.

OBJECTIVES: To describe a new hypothesis for the initial events leading to urinary stones. A biomechanical perspective on Randall's plaque formation through form and function relationships is applied to functional units within the kidney, we have termed the 'medullo-papillary complex' - a dynamic relationship between intratubular and interstitial mineral aggregates. METHODS: A complete MEDLINE search was performed to examine the existing literature on the anatomical and physiological relationships in the renal medulla and papilla. Sectioned human renal medulla with papilla from radical nephrectomy specimens were imaged using a high resolution micro X-ray computed tomography. The location, distribution, and density of mineral aggregates within the medullo-papillary complex were identified. RESULTS: Mineral aggregates were seen proximally in all specimens within the outer medulla of the medullary complex and were intratubular. Distal interstitial mineralisation at the papillary tip corresponding to Randall's plaque was not seen until a threshold of proximal mineralisation was observed. Mineral density measurements suggest varied chemical compositions between the proximal intratubular (330 mg/cm3 ) and distal interstitial (270 mg/cm3 ) deposits. A review of the literature revealed distinct anatomical compartments and gradients across the medullo-papillary complex that supports the empirical observations that proximal mineralisation triggers distal Randall's plaque formation. CONCLUSION: The early stone event is initiated by intratubular mineralisation of the renal medullary tissue leading to the interstitial mineralisation that is observed as Randall's plaque. We base this novel hypothesis on a multiscale biomechanics perspective involving form and function relationships, and empirical observations. Additional studies are needed to validate this hypothesis.

National Trends in Secondary Procedures Following Pediatric Pyeloplasty.

PURPOSE: Although reported success rates after pediatric pyeloplasty to correct ureteropelvic junction are high, failure may require intervention. We sought to characterize the incidence and timing of secondary procedures after pediatric pyeloplasty using a national employer based insurance database. MATERIALS AND METHODS: Using the MarketScan® database we identified patients 0 to 18 years old who underwent pyeloplasty from 2007 to 2013 with greater than 3 months of postoperative enrollment. Secondary procedures following the index pyeloplasty were identified by CPT codes and classified as stent/drain, endoscopic, pyeloplasty, nephrectomy or transplant. The risk of undergoing a secondary procedure was ascertained using Cox proportional hazards models adjusting for demographic and clinical characteristics. RESULTS: We identified 1,976 patients with a mean ± SD followup of 23.9 ± 19.8 months. Overall 226 children (11.4%) had undergone at least 1 post-pyeloplasty procedure. The first procedure was done within 1 year in 87.2% of patients with a mean postoperative interval of 5.9 ± 11.1 months. Stents/drains, endoscopic procedures and pyeloplasties were noted in 116 (5.9%), 34 (1.7%) and 71 patients (3.1%), respectively. Length of stay was associated with undergoing a secondary procedure. Compared with 2 days or less the HR of 3 to 5 and 6 days or greater was 1.65 and 3.94 (p = 0.001 and <0.001, respectively). CONCLUSIONS: Following pediatric pyeloplasty 1 of 9 patients undergoes at least 1 secondary procedure with the majority performed within the first year. One of 11 patients undergoes intervention more extensive than placement of a single stent or drain, requiring management strategies that generally signify recurrent or persistent obstruction. Estimates of pyeloplasty success in this national data set are lower than in other published series.