Predictors of spontaneous ureteral stone passage in the presence of an indwelling ureteral stent

Abstract

Patients presenting acutely with obstructing stones often have a ureteral stent placed as a temporizing solution. Ureteroscopy is then commonly performed in a staged fashion, but occasionally the stone is found to have passed. We aimed to identify the frequency and predictors of ureteral stone passage with a stent in place. Records were reviewed to identify patients who had a stent placed for a single ureteral stone. Subsequent ureteroscopy or CT scan was used to ascertain stone passage. Effect of age, gender, BMI, stone diameter, alpha blocker use, urinary tract infection, hydronephrosis, and stent duration on stone passage was assessed. Inclusion and exclusion criteria were met in 209 patients. Mean maximum stone diameter was 6.5 ± 2.5 mm. Passage rates for stones < 3 mm, 3–4.9 mm, 5–6.9 mm, and ≥ 7 mm were 50%, 13%, 10%, and 0%, respectively. The overall rate of passage was 8%. Stone passage was associated with smaller maximum stone diameter, more distal stone location, and longer duration of stent before ureteroscopy/CT on univariate analysis (p < 0.01). Stone diameter and stent duration remained significantly associated on multivariable analysis (p = 0.001 and p = 0.05, respectively). Our findings suggest ureteral stone passage with a concurrent ureteral stent is not a rare event as it occurred in 14% of stones less then 7 mm in maximum diameter. Stone size and duration of stent before ureteroscopy or CT were found to be independent predictors of passage. Select patients with small ureteral stones who have been stented should be considered for a trial of urine straining or repeat imaging before subsequent ureteroscopy.