Research Original Investigation

Shock Wave Lithotripsy and Ureteroscopy

Invited Commentary

Why Does Anyone Get Shock Wave Lithotripsy? John L. Gore, MD, MS

Urinary stone disease is an important public health burden. Concomitant with other obesity-related conditions on the rise in the United States, this onus is increasing,1 and understanding best practices for effective management of kidney and ureteral stones would promote high-quality care for millions of Americans. In this issue of JAMA Surgery, Scales et al2 applied instrumental variable analysis—an econometric technique that addresses confounding by the variables you can measure, such as age and comorbidity, as well as the unmeasured variRelated article page 648 ables whose confounding can typically be addressed only through randomization—to compare the effectiveness of ureteroscopy (URS) and shock wave lithotripsy (SWL). The authors found that URS was associated with lower rates of retreatment within 4 months of the initial surgery. So does this answer the question whether URS is better than SWL for treating urinary tract stones? The answer is no.


The need for retreatment of urinary tract stones affected less than one-quarter of the patients identified; for many patients, SWL was successful. This comparison applies to the marginal patient, a concept unique to instrumental variable analysis, in which treatment effects are estimated for patients for whom the instrument determines the treatment received.3 So, URS was clearly superior among patients in whom treatment was determined by their differential distance to an SWL provider or by the density of urologists or surgeons in their geographic area. However, the work by Scales et al indicates that SWL is an overused modality. The motivations likely derive more from provider factors than from patient preferences, drivers such as surgeon inexperience with URS and surgeon ownership stake in SWL machines. Most important, the study by Scales et al indicates that we need to better identify the treatments that work for patients with urinary tract stone disease based on their personal characteristics and the size, location, and composition of their stones.


Conflict of Interest Disclosures: None reported.

Author Affiliation: Department of Urology, University of Washington, Seattle.


Corresponding Author: John L. Gore, MD, MS, Department of Urology, University of Washington, 1959 NE Pacific St, PO Box 356510, Seattle, WA 98195 ([email protected]).

1. Scales CD Jr, Smith AC, Hanley JM, Saigal CS; Urologic Diseases in America Project. Prevalence of kidney stones in the United States. Eur Urol. 2012; 62(1):160-165.

Published Online: May 16, 2014. doi:10.1001/jamasurg.2014.340.

2. Scales CD Jr, Lai JC, Dick AW, et al; Urologic Diseases in America Project. Comparative effectiveness of shock wave lithotripsy and

ureteroscopy for treating patients with kidney stones [published online May 16, 2014]. JAMA Surg. doi:10.1001/jamasurg.2014.336. 3. Stukel TA, Fisher ES, Wennberg DE, Alter DA, Gottlieb DJ, Vermeulen MJ. Analysis of observational studies in the presence of treatment selection bias: effects of invasive cardiac management on AMI survival using propensity score and instrumental variable methods. JAMA. 2007;297(3):278-285.

JAMA Surgery July 2014 Volume 149, Number 7

Copyright 2014 American Medical Association. All rights reserved.

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Why does anyone get shock wave lithotripsy?

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