Category: Clinical Stones: Outcomes

MP8-20 - Retreatment after Ureteroscopy and Shockwave Lithotripsy: A Population-based Pseudo-Randomized Comparative Effectiveness Study

Fri, Sep 21
10:00 AM - 12:00 PM

Introduction & Objective :

Ureteroscopy (URS) and shockwave lithotripsy (SWL) are the most commonly performed surgical interventions for kidney and ureteral stones. However, the comparative effectiveness of these interventions at the population level is unclear as prior studies have been performed in younger, commercially insured populations and have estimated retreatment for the marginal rather than the average patient. We sought to determine the risk of retreatment after SWL and URS among all patients undergoing these surgeries in South Carolina.


Methods :

Using all payer billing data from 74 hospitals in South Carolina, we performed a series of pseudo-randomized trials to determine the risk of retreatment within 6 months of URS or SWL between 1994 and 2016. To account for confounding between surgical interventions, we first fit a propensity score model for each year’s data to predict the probability of undergoing SWL conditional on hospital-level and patient-level covariates. Next, a discrete time failure model was fit using inverse probability weighted logistic regression which accounted for repeated observations of the same patient across multiple trials and balanced measured confounders across treatment groups. Odds Ratios (OR), 95% confidence intervals, and probabilities of retreatment were estimated.


Results :

From 1997-2016, 123,970 children and adults underwent SWL (n=74,235; 59.9%) or URS (n=49,735; 40.1%), of whom 12,208 patients (9.9%) underwent retreatment with SWL and/or URS within 6 months. 73% of retreatments occurred within 2 months of the original surgery. The probability of retreatment was 7.5% for URS and 10.4% for SWL (number of SWL needed to retreat, 33). Compared to initial URS, initial SWL was associated with a 44% increased odds of retreatment (95% CI 1.36, 1.51) within 6 months of initial surgery. SWL (vs. URS) was always associated with a greater odds of retreatment over the 6-month period, but the magnitude of the association varied significantly across the follow-up time. SWL had the greatest risk for retreatment compared to URS at months 2 (OR 2.09, 95% CI 1.86, 2.35) and 3 (OR 1.98, 95% CI 1.70, 2.31).  Of those patients who had retreatment, patients who had initial SWL were more likely to have SWL for retreatment (84.6%) than were patients who had initial URS to have URS for retreatment (29.3%).


Conclusions : Compared to URS, SWL was associated with a substantially increased odds of retreatment among the population of South Carolina over a 20 year period. However, the probability of retreatment for the average patient was modest for both URS (7.5%) and SWL (10.4%).

Gregory E. Tasian

Assistant Professor of Urology and Epidemiology
The Children's Hospital of Philadelphia
Philadelphia, Pennsylvania

Gregory Tasian, MD, MSc, MSCE is an Assistant Professor of Urology and Epidemiology and a Senior Scholar in the Center for Clinical Epidemiology and Biostatistics at the University of Pennsylvania Perelman School of Medicine. His clinical practice and research program are based at the Children’s Hospital of Philadelphia (CHOP), where he has faculty appointments in the Division of Urology and the Center for Pediatric Clinical Effectiveness. He is a practicing pediatric urologist with a clinical focus on kidney stone disease, and is Surgical Director of the Pediatric Kidney Stone Center at CHOP. His research is devoted to decreasing the lifetime burden of kidney stone disease, with a particular emphasis on clinical trials of interventions to improve health behaviors to decrease kidney stone recurrence, comparative effectiveness of surgical interventions for kidney stones, the environmental epidemiology of nephrolithiasis, and understanding the role of the gut microbiome in kidney stone disease. He also has an active research program in imaging classification and predictors of chronic kidney disease (CKD) progression for children with congenital abnormalities of the kidney and urinary tract.

John Kim

Medical Student
SUNY Downstate
New York, New York

Lihai Song


Philadelphia, Pennsylvania

Jennifer Faerber


Philadelphia, Pennsylvania