Prediction for spontaneous passage of ureteral stones with indwelling ureteral stent: PASS score

To develop a predictive model for the spontaneous passage of ureterolithiasis in patients with indwelling ureteral stents.

In this retrospective cohort study, we reviewed all patients with ureterolithiasis who underwent ureteral stent placement at our institution from 2015 to 2021. Stone Characteristics, including stone location, density, shape, and diameter, were evaluated using computed tomography (CT). Low-density was defined as < 1000 Hounsfield units (HU). Spontaneous stone passage (SSP) was determinded by follow-up CT imaging or ureteroscopy. Multivariable logistic regression with backward selection was applied to identify predicts of SSP and to construct a predictive model.

Among 401 patients, 97 (24.2%) experienced SSP after a median follow-up of 26 days (Interquartile Range [IQR] 23-32). Independent predictors for SSP included low stone density < 1000 (Odds Ratio [OR] 7.45, 95% Confident Interval [CI] 2.79-25.94, p = < 0.001), location at the ureterovesical junction (OR 5.28, 95% CI 2.66-10.93, p = < 0.001), mid to distal ureteral location (OR 2.08, 95% CI 1.03-4.31, p = 0.013) and stone diameter ≤ 5 mm (OR 3.42, 95% CI 1.58-7.94, p = < 0.001). Using these predictors, we developed a three-item PASS Score to estimate the probability of SSP.

Approximately a quarter of ureteral stones passed spontaneously within 4 weeks of stent placement. The PASS score provides a practical tool for clinicians to estimate the likelihood of SSP and guide personalized treatment planning. External validation is required to confirm its clinical utility.