Temporal Trends in the Use of Percutaneous Nephrolithotomy David S. Morris, John T. Wei,* David A. Taub, Rodney L. Dunn, J. Stuart Wolf, Jr. and Brent K. Hollenbeck† From the Department of Urology and Division of Clinical Research and Quality Assurance, University of Michigan, Ann Arbor, Michigan Purpose: Treatment for nephrolithiasis has evolved because of the dissemination of less invasive techniques, such as ureteroscopy and shock wave lithotripsy. We examined temporal trends in PCNL use and characterized the determinants of a prolonged LOS and in-hospital mortality to provide insight into the evolution of practice patterns for nephrolithiasis treatment. Materials and Methods: We abstracted data on 12,948 patients undergoing percutaneous procedures for urinary calculi between 1988 and 2002 from the Nationwide Inpatient Sample using International Classification of Disease, 9th revision, Clinical Modification procedure and diagnostic codes. A weighted sample was used to estimate national PCNL use rates. Adjusted models were constructed to measure the association of hospital structure and patient demographics with mortality and a prolonged LOS (greater than 90th percentile). Results: Annual PCNL use increased temporally during the study from 1.2/100,000 to 2.5/100,000 United States residents (p 0.0001). The in-hospital mortality rate was low at 0.2%, although a volume-outcome relationship was still evident (high and low volume 0.1% and 0.2%, respectively, p = 0.002). Treatment at hospitals with lower hospital PCNL volume and lower discharge volume (all diagnoses) was associated with an increasing likelihood of in-hospital mortality (each p 0.01). Conclusions: Despite the advent of less invasive techniques PCNL remains a popular means of managing stone disease. Although mortality was rare, it was significantly lower at high than at low volume hospitals. Low short-term mortality rates coupled with shorter LOS and high success rates may make PCNL increasingly palatable from a patient perspective and provide a potential basis for its increasing use. Key Words: urinary calculi, physician’s practice patterns, quality of health care U rolithiasis is a common disease with a lifetime prev- alence of 6% and 4% in men and women, respec- tively, in the United States. 1 The significance of the disease is further underscored by its increasing prevalence 1 and the economic impact of its treatment, which was esti- mated to cost approximately $2 billion in 2000. 1,2 The dissemination of less invasive treatments, including percu- taneous, 3 endoscopic 4 and resonance based techniques, 5 has revolutionized the contemporary management of urolithia- sis. Relative to open stone surgery these less invasive therapies are associated with lower morbidity and hospital- ization requirements. 6,7 However, their use must be bal- anced with variable stone-free rates and the need for outpatient convalescence. Guidelines and recommendations for PCNL have been largely based on nonrandomized studies. 8,9 Thus, significant practice variation and its inherent implications on the vari- ability of the quality of care delivered are of great concern. 10 Relative to other minimally invasive stone therapies, eg ureteroscopy and SWL, PCNL is more likely to result in postoperative morbidity 11 and yet it is also more likely to result in successful treatment when used as monotherapy. 12 Given this potential trade-off, we characterized practice pat- tern variation in the use of PCNL and in its short-term outcomes using a nationally representative data set to iden- tify potential gaps in the quality of care. Such information would be uniquely advantageous for developing future qual- ity improvement initiatives and potentially characterizing quality of care indicators. MATERIALS AND METHODS Subjects From the NIS Data from the Healthcare Cost and Utilization Project NIS were abstracted for 1988 though 2002. The NIS represents a 20% stratified sample of all hospital discharges in the United States and it is maintained by the Agency for Health- care Research and Quality. Data on eligible subjects were abstracted using diagnostic and procedural terminology based on ICD-9 codes in 2 steps. Patients with primary diagnostic codes for urolithiasis (274.11 for uric acid neph- rolithiasis, 592 for calculus of the kidney and ureter, 592.0 for calculus of the kidney and 592.9 for unspecified urinary calculus) were identified. In this cohort those undergoing PCNL were selected using the appropriate ICD-9 procedural codes (5504 for percutaneous nephrostomy with fragmenta- tion and 5503 for percutaneous nephrostomy in combination with 5521 for nephroscopy). Secondary ICD-9 diagnostic codes were abstracted to enumerate comorbid conditions according to the Romano modification of the Charlson co- Submitted for publication July 1, 2005. * Financial interest and/or other relationship with Sanofi, Laser- scope, Calypso and Boehringer Ingelheim. † Correspondence: Department of Urology, Taubman Health Care Center 3875-0330, University of Michigan Health System, 1500 East Medical Center Dr., Ann Arbor, Michigan 48109-0330 (tele- phone: 734-615-0563; FAX: 734-936-9127; e-mail: bhollen@umich. edu). 0022-5347/06/1755-1731/0 Vol. 175, 1731-1736, May 2006 THE JOURNAL OF UROLOGY ® Printed in U.S.A. Copyright © 2006 by AMERICAN UROLOGICAL ASSOCIATION DOI:10.1016/S0022-5347(05)00994-8 1731