Renal colic is generally considered a diagnosis appropriate for discharge home once pain is adequately controlled and no other admission criteria are met. The increasing prevalence of ED observation units (EDOU) represent another disposition option for patients with renal colic. In this study, we sought to describe the rates of 14-day revisits for renal colic among patients placed in an EDOU as compared to those discharged from the ED.

This is a retrospective observation study of ED patients with renal colic between 2016 and 2024. Adult patients 21 years and older with renal colic were included. Patients were excluded if they were admitted to the hospital during their ED visit. The cohort was divided into those who were discharged from the ED and those who were placed in an EDOU. The primary outcome was the rate of 14-day ED revisits for renal colic after discharge. We also describe the rate of 14-day “serious” ED revisits, defined as a revisit that required admission to the hospital or required urological intervention.

N = 1836 patients were included; 1376 in the ED discharge cohort and 460 in the EDOU cohort. Patients in the ED observation cohort were more likely to have a larger stone size (>5 mm), moderate-severe hydronephrosis, and a proximal stone location (ureteropelvic junction or ureteral) but were otherwise demographically similar. The overall rate of 14-day revisits in the cohort was 162 (8.8 %), 119 (8.6 %) in the discharge cohort and 43 (9.3 %) in the EDOU cohort (difference = −0.7 %, 95 % confidence interval −3.7 % to 2.3 %). The rate of serious 14-day revisits was 64 (3.8 %), 47 (3.4 %) in the discharge cohort and 17 (3.7 %) in the EDOU cohort (difference = −0.3 %, 95 % confidence interval −2.2 % to 1.7 %).

We did not identify a difference in 14-day revisits or serious revisits for patients with renal colic who were placed in an EDOU compared to those who were discharged from the ED. However, we found that patients placed in the EDOU had higher-risk stone features (size, location, degree of obstruction), and yet despite this, had similar rates for revisits.