Systematic radiologic detection of kidney stones in Canadian children: a new era of asymptomatic stones?

INTRODUCTION: Asymptomatic, or incidental, pediatric kidney stones detected on abdominal imaging pose a clinical challenge as their significance and expected outcome are not well described. OBJECTIVE: Our primary objective was to estimate the incidence of nephrolithiasis in pediatric patients undergoing abdominal ultrasound (US) or computerized tomography (CT), for all indications, in a pediatric tertiary care hospital. Our secondary objective was to determine the clinical outcome of these radiographically detected stones. METHODS: All abdominal US or CT radiology reports for patients younger than 18 years between January 1, 2011, and December 31, 2016, were retrieved. Reports were automatically flagged using textual analysis if they contained one of the 32 keywords potentially indicating nephrolithiasis. Flagged reports, as well as 10% of unflagged reports, were reviewed to confirm the radiologist impression of presence or absence of stones. Patient and stone-related clinical data were extracted. RESULTS: Two thousand four hundred forty-nine (5%) of 53 235 imaging reports cited at least one of the keywords. Manual review of flagged reports identified 498 studies having a radiologist impression of stones (244 unique patients). Stone incidence in children undergoing abdominal imaging more than doubled between 2011 and 2016. Medical record review found that 140 patients (57%) were symptomatic, while the other 104 patients (43%) were asymptomatic. Spontaneous resolution was greater (57% vs 34%) in asymptomatic patients compared to symptomatic patients. Asymptomatic patients were younger with a median age of 0.6 compared to 12.3 years. Asymptomatic and symptomatic stones were followed up for similar lengths of time (2.3 vs 2.0 years, p > 0.05) and had a similar number of follow-up USs (3.9 vs 4.6 studies, p > 0.05). CONCLUSIONS: The incidence of radiologically identified stones in children undergoing abdominal imaging at our center increased over time. Asymptomatic stones follow a benign course with minimal need for intervention; however, they were detected almost as frequently as symptomatic stones. Asymptomatic stones may represent increased healthcare resource utilization due to similar follow-up compared to symptomatic stones. Further research regarding the optimal imaging intervals and long-term follow-up for asymptomatic stones is warranted.