Radiological imaging of patients with suspected urinary tract stones: national trends, diagnoses, and predictors

Abstract

Objectives: Overutilization of computed tomography (CT) is a growing public health concern due to increasing health care costs and exposure to radiation; these must be weighed against the potential benefits of CT for improving diagnoses and treatment plans. The objective of this study was to determine the national trends of CT and ultrasound (US) utilization for assessment of suspected urolithiasis in emergency departments (EDs) and if these trends are accompanied by changes in diagnosis rates for urolithiasis or other significant disorders and hospitalization rates.

Methods: This was a retrospective cross-sectional analysis of ED visits from the National Hospital Ambulatory Medical Care Survey (NHAMCS) between 1996 and 2007. The authors determined the proportion of patient visits for flank or kidney pain receiving CT or US testing and calculated the diagnosis and hospitalization rates for urolithiasis and other significant disorders. Patient-specific and hospital-level variables associated with the use of CT were examined.

Results: Utilization of CT to assess patients with suspected urolithiasis increased from 4.0% to 42.5% over the study period (p < 0.001). In contrast, the use of US remained low, at about 5%, until it decreased beginning in 2005 to 2007 to 2.4% (p = 0.01). The proportion of patients diagnosed with urolithiasis (approximately 18%, p = 0.55), with other significant diagnoses (p > 0.05), and admitted to the hospital (approximately 11%, p = 0.49) did not change significantly. The following characteristics were associated with a higher likelihood of receiving a CT scan: male sex (odd ratio [OR] = 1.83, 95% confidence interval [CI] = 1.22 to 2.77), patients presenting with severe pain (OR = 2.96, 95% CI = 1.14 to 7.65), and those triaged in 15 minutes or less (OR = 2.41, 95% CI = 1.08 to 5.37). CT utilization was lower for patients presenting to rural hospitals (vs. urban areas; OR = 0.34, 95% CI = 0.19 to 0.61) and those managed by a nonphysician health care provider (OR = 0.19, 95% CI = 0.07 to 0.53).

Conclusions: From 1996 to 2007, there was a 10-fold increase in the utilization of CT scan for patients with suspected kidney stone without an associated change in the proportion of diagnosis of kidney stone, diagnosis of significant alternate diagnoses, or admission to the hospital.