Login to Access Video or Poster Abstract: MP01-02
Sources of Funding: None

Introduction

Medical expulsive therapy (MET) is frequently used for patients with ureteral stones who present to the emergency department (ED). Our goal was to develop and validate a nomogram to predict the probability stone passage on MET for ureteral stones.

Methods

We reviewed ED visits within our health system with an ICD-9 diagnosis of urolithiasis, an associated CT scan, and discharged on MET between 2010-2013. CT's were reviewed to confirm stone size, location, and associated hydronephrosis. The primary outcome was spontaneous stone passage within 90-days of initial ED visit. Patients with no documented follow up in our system were called to collect data on stone passage. A nomogram was developed using variables chosen for clinical and statistical significance and validated internally using a bootstrapping technique.

Results

1,424 ED visits met the inclusion criteria and of these, 1,146 (80.4%) had confirmed ureteral stones on CT. Patients lost to follow up and who were unreachable by phone were excluded, leaving 661 patients to build the final model. The median age was 50 years (IQR 38-59) with 419 (63.4%) males and a median stone size of 4.0 mm (IQR 3.0-5.2). A majority of patients, 422 (64%), spontaneously passed their stone while the remaining underwent a procedure. On univariable analysis, patients who passed stones tended to have smaller stones (3.6 mm vs 5.2 mm, p < 0.001), stones in the distal ureter (73% vs. 41%, p < 0.001), and significantly higher WBC counts (9.49 vs. 8.57, p < 0.001). There were no associations between age (49 vs. 50, p = 0.831) or gender (64% male vs. 62% male, p = 0.451) on stone passage. In the multivariable model, stone size (per 1 mm increase; OR 0.49, 95% CI 0.43-0.57, p < 0.001), stone location (p < 0.0001), a prior history of stone passage (OR 1.74, 95% CI 1.04 - 2.93, p = 0.036), and WBC count (per 1k/uL increase, OR 1.12, 95% CI 1.04-1.21, p = 0.001) were significantly associated with spontaneous stone passage. The model was validated internally (bootstrap-adjusted concordance index, 0.80) and demonstrated excellent calibration.

Conclusions

For patients presenting with ureteral stones in the ED amenable to observation, we have developed a model to predict the probability of stone passage. Early follow-up or intervention for patients with a low probability of stone passage could improve patient satisfaction and prevent costly ED returns.

Funding

None