Predictive Factors for Ureteral Stone Passage in Children

Objective: To determine if transverse or longitudinal ureteral stone length is associated with the rate of spontaneous stone passage in a pediatric population. Methods: A retrospective cohort study was performed of children presenting with a ureteral calculus to a single institution from 2010 to 2020. Inclusion criteria included a symptomatic ureteral stone diagnosed by CT. Images were independently reviewed by two pediatric radiologists. An effective stone passage was defined if a patient did not require surgical intervention and follow-up imaging within 6 weeks confirmed the absence of the stone. Univariate and multivariate logistic regression analysis was performed. Results: A total of 66 subjects (34 female) with a mean age of 14.5 years were included. Fifty-one (77%) were treated with medical expulsive pharmacotherapy. A total of 31/66 (47%) patients passed the stone spontaneously, whereas 35 underwent surgical intervention within 6 weeks. Both longitudinal (odds ratio [OR] = 1.9, 95% confidence interval [CI]: 1.2-3.0) and transverse (OR = 2.6, 95% CI: 1.5-4.7) stone dimensions were associated with likelihood of spontaneous passage on univariable logistic regression. On multivariable regression, transverse stone diameter (OR = 2.5, 95% CI: 1.3-4.5) and history of nephrolithiasis (OR = 4.3, 95% CI: 1.1-17) were the only independent predictors of stone passage. Based on Receiver Operator Curve (ROC) analysis, a transverse diameter of 3.5 mm was optimal to predict stone passage (area under the curve = 0.82, sensitivity = 84%, specificity = 77%). Conclusions: A ureteral stone measuring less than 3.5 mm in transverse dimension is more likely to pass spontaneously in children. CT scans should report ureteral stone dimensions in the transverse plane.