Determinants of treatment pathway in renal colic: a size-stratified analysis from the emergency department of a tertiary center.

Acute flank pain due to ureteral calculi is a common presentation in emergency departments (EDs). Decisions between conservative management and inpatient intervention remain difficult in the absence of absolute indications. This study aims to identify size-stratified predictors to assist ED decision-making in ureterolithiasis. This was a single-center retrospective study of patients presenting in the ED of a tertiary center with acute renal colic between October 2020 and November 2024. A total of 752 patients with CT-confirmed ureteral stones were included and analyzed. Receiver operating characteristic (ROC) analysis identified a 5.65-mm threshold; operationalized as 6 mm in the subsequent analyses. After size-based stratification, uni- and multivariate regression analyses were conducted to identify predictors for inpatient admission in the <6 mm subgroup and predictors for discharge in the ≥6 mm subgroup, respectively. Overall, 77% of 1,194 patients were discharged and managed conservatively, and 23% underwent inpatient intervention. In the < 6 mm subgroup (n = 514; 20% intervened), multivariable analysis identified larger stone diameter (OR 1.65 per mm, 95% CI 1.09–2.59; p = 0.021, lower eGFR (OR 0.95 per mL/min, 95% CI 0.91–0.98; p = 0.002) and younger age (OR 0.96 per year, 95% CI [0.92, 0.99]; p = 0.024) as independent predictors for intervention. In the ≥ 6 mm subgroup (n = 238; 45% discharged), a distal location was the only independent predictor of discharge (OR 5.33, 95% CI 1.12–31.3; p = 0.045). A pragmatic 6-mm threshold, complemented by basic presentation markers, refines ED management beyond size alone. For stones < 6 mm, greater diameter and reduced renal function independently signaled the need for inpatient intervention, whereas age was inversely associated. For stones ≥ 6 mm, predominantly distal location favored discharge.