Emergency department non-contrast computed tomography for suspicion of obstructive urolithiasis: Yield and consequences

Introduction: We aimed to analyze patterns of referral, yield, and clinical implications of noncontrast computed tomography (NCCT) in the acute evaluation of flank pain suspected as obstructive urolithiasis (OU) in a high-volume emergency department (ED). Methods: The study comprised 506 consecutive NCCTs performed in the ED over four months. Detection rates of OU, incidental, and alternative findings were calculated. Imaging signs suspicious for recent passage of stones were considered positive for OU, while renal stones without signs of obstruction were considered unrelated to the acute presentation. OU, other findings requiring hospitalization, and incidental findings warranting further workup were considered situations in which NCCTs were warranted. Results: NCCTs confirmed an OU diagnosis in 162 (32%) patients and non-clinically significant nephrolithiasis in 125 (25%). They revealed other findings in 108 (21%) patients, including 42 (8%) with clinically significant incidental findings and 26 (5%) with alternative diagnoses requiring hospitalization. NCCTs were entirely negative in 111 (22%) patients. Corroboration of these outcomes, together with overlapping of OU, incidental, and alternative significant findings in some patients resulted in an overall justified NCCT request rate of 44%. Conclusions: The yield of NCCT performed in acute presentations of flank pain suspected as OU is relatively low, and over one-half of the scans are unwarranted. The pattern of requesting NCCT in the ED needs refinement to avoid abuse that may lead to radiation overexposure, psychological burden, physical harm, and financial overload.