Diagnostic Imaging for Suspected Nephrolithiasis in United States Emergency Departments

CT and ultrasound (US) are primary imaging modalities for evaluating flank pain and suspected nephrolithiasis in emergency departments (EDs). Prior evidence suggests that initial US instead of CT reduces radiation exposure without serious clinical consequences. We investigated trends in imaging used for evaluating flank pain in United States EDs.

ED encounters for flank pain were identified in the National Hospital Ambulatory Medical Care Survey (2014-2022). National estimates were generated through multistage survey weighting. Multivariate logistic regression models controlling for demographic and visit characteristics were used to calculate adjusted odds ratios (aORs) and α = .01.

Among an estimated 25.4 million ED encounters for flank pain, 24.2% resulted in a nephrolithiasis diagnosis. The annual rate of nephrolithiasis diagnoses was similar throughout the study period. Imaging utilization included CT-exclusive (53.3%), US-exclusive (5.6%), combined CT and US (4.6%), and neither CT nor US (36.4%) workups. CT-exclusive (aOR: 1.050, P = .009) and combined CT and US (aOR: 1.175, P = .001) workups increased over time, while encounters without imaging declined (aOR: 0.945, P = .006). US-exclusive workup remained constant over time. Revisit status (aOR: 0.447, P < .001), Black race (aOR: 0.631, P = .002), and care at teaching hospitals (aOR: 0.721, P = .004) were significantly negatively associated with CT-exclusive workup. Younger age (aOR: 0.973, P < .001) and care at teaching hospitals (aOR: 1.982, P = .005) were significantly associated with US-exclusive workup.

CT remains the predominant imaging modality for flank pain evaluation and has increased in use since 2014, while US-exclusive evaluation remains limited to select settings and patient populations.