Epidemiological Trends in Pediatric Urolithiasis at United States Freestanding Pediatric Hospitals Jonathan C. Routh,*,† Dionne A. Graham and Caleb P. Nelson From the Department of Urology (JCR, CPN) and Clinical Research Program (DAG), Children’s Hospital Boston and Harvard Pediatric Health Services Research Fellowship Program (JCR), Harvard Medical School, Boston, Massachusetts Abbreviations and Acronyms ICD-9-CM = International Classification of Diseases, 9th revision, clinical modification KID = Kids’ Inpatient Database PHIS = Pediatric Health Information System Submitted for publication December 27, 2009. Study received institutional review board ap- proval from Children’s Hospital Boston and ad- ministrative approval from Pediatric Health Infor- mation System. * Supported by Grant T32-HS000063 from Agency for Healthcare Research and Quality. † Correspondence: Department of Urology, Children’s Hospital Boston, 300 Longwood Ave., HU-355, Boston, Massachusetts 02115 (tele- phone: 617-355-6526; FAX: 617-730-0474; e-mail: jon.routh@gmail.com). Purpose: Anecdotal and lay press reports suggest that the incidence of pediatric urolithiasis is increasing but reliable data are lacking. The objective of this study was to examine trends in the epidemiology of urolithiasis at pediatric hospitals nationwide. Materials and Methods: The Pediatric Health Information System database is a national database covering 42 freestanding United States pediatric hospitals that captures inpatient admissions, and emergency department and outpatient sur- gery visits. We searched the Pediatric Health Information System database to identify children (18 years old or younger) treated for urolithiasis between 1999 and 2008. Patients with urolithiasis were measured as a proportion of the total number of patients seen per hospital annually. Trends were verified by compar- ing results to 2 other common pediatric diagnoses—appendicitis and viral bron- chiolitis. Results: We identified 7,921 children diagnosed with urolithiasis during the study period. The total number of children with urolithiasis seen in Pediatric Health Information System hospitals increased from 125 in 1999 to 1,389 in 2008. Mean number of stone cases per hospital per year increased from 13.9 to 32.6. Compared to total hospital patients, the proportion of patients with pediatric urolithiasis increased from 18.4 per 100,000 in 1999 to 57.0 per 100,000 in 2008, an adjusted annual increase of 10.6% (p 0.0001). Urolithiasis also increased compared to appendicitis (p 0.0001) and bronchiolitis (p 0.0001). Conclusions: Even after correcting for increases in total patient volume at Pe- diatric Health Information System hospitals, there has been a significant in- crease in the number of children diagnosed with and treated for urolithiasis at these hospitals in the last decade. Key Words: epidemiology, nephrolithiasis, pediatrics, urolithiasis NUMEROUS lay press reports have re- cently suggested that the incidence of pediatric urolithiasis is increasing, based primarily on anecdotal evi- dence from large academic medical centers. 1,2 The mechanisms underly- ing this increase are purported to in- clude increased rates of overweight and obesity, excessive animal protein and caloric intake, and increased di- etary sodium intake in United States children, all of which have been linked to an increase in urolithiasis diagnoses among adults. 3–5 Several studies have shown an increased inci- dence of urolithiasis among adults, and these observations have often been assumed to be true for children as well. However, other than anec- dotal reports, few rigorous studies have demonstrated an increase in the number of stone diagnoses through 1100 www.jurology.com 0022-5347/10/1843-1100/0 Vol. 184, 1100-1105, September 2010 THE JOURNAL OF UROLOGY ® Printed in U.S.A. © 2010 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION AND RESEARCH,INC. DOI:10.1016/j.juro.2010.05.018