MP40-19 METABOLIC STONE WORK-UP IN CHILDREN: WHAT DOES IT TELL US AND HOW IS IT UTILIZED?

Abstract

INTRODUCTION AND OBJECTIVES: Lower pole renal stones in children, usually present as an incidental finding. In general the need for intervention is rare but the precise frequency is unknown. Here in we evaluate the outcome of lower pole renal stones in children. METHODS: After Research Ethics Board (REB) approval, we performed a retrospective review of charts and renal ultrasounds of children with lower pole stones seen in Urology clinic at The Hospital for Sick Children over a period of 14 years. Complex renal malformations as horseshoe kidney, solitary kidney, solitary functioning kidney and cross-fused ectopia were excluded. Our goals are: 1) to determine factors that might predict the need for stone intervention (type of stones, underlying metabolic disease, size, and growth rate); 2) to calculate the success rate of non-operative management. RESULTS: One hundred and eight children with nephrolithiasis were initially screened. Forty six (42.6%) found to have lower pole stones. Mean age at presentation was 112.6 61.5 months. Twenty six patients (56.5%) were boys. Thirty six children (78.2%) had only 1 or 2 lower pole stones. Mean time of follow-up was 4.3 3.7 years. The difference between mean size of the lower pole stones in ultrasound (US) at presentation vs. last visit for patients followed conservatively was not statistically significant (6.9 3.2 mm vs. 7.38 4.5 mm, respectively ; ANOVA p1⁄40.1). Twenty one patients (45.6%) were symptomatic (renal colic and/or gross hematuria). From those, 10 passed stones (2 calcium phosphate, 5 calcium oxalate, 1 cystine, 1 uric acid, and 1 struvite). Twenty five (54.3%) children had surgery for stone removal (9 had extracorporeal shock wave lithotripsy, 14 ureteroscopy, 1 open nephrolithotomy and 1 nephrectomy). From those, 16 (64%) had stone growth over-time and significantly larger stones (10.6 5.5 mm) at baseline US. Five had percutaneous nephrolithotomy as second surgical procedure. Vast majority (90.9%) were calcium phosphate or calcium oxalate stones. CONCLUSIONS: Our data suggests that lower pole stones could be followed conservatively. Initial stone size greater than 10.6 5.5 mm and stone growth over-time are significant risk factors that might predict the need for surgical intervention.