Association of magnetic resonance imaging for back pain on seven-day return visit to the Emergency Department.

BACKGROUND: The prevalence of back pain is rising, as is the use of high-cost imaging in the ED. The objective of our study was to determine if an MRI in the ED for patients with back pain resulted in a lower incidence of ED return visit and to determine if these patients had longer ED length of stay (LOS) and use of ED observation.

METHODS: A retrospective cohort study of consecutive patients seen with back pain was conducted at an urban, university-affiliated ED between 1 January 2012 and 11 July 2014. The association of MRI on return within 7 days was assessed using a χ2 test and a multivariable logistic regression model and the difference in median ED LOS was compared using a Wilcoxon rank-sum test.

RESULTS: During the study period, 6094 patients were evaluated in the ED with back pain as the primary diagnosis. Of these, 797 (13%) received an MRI. Among all patients with back pain, 277 (4.5%) returned within 7 days. Univariate analysis found that patients who received an MRI were no less likely to return within 7 days than patients who did not (4.3% vs 4.6%; p=0.68). Patients who had an MRI were more likely to be admitted to observation (74.2% vs 10.8%; p<0.0001) and had a longer ED LOS (median 4.8 hours vs 2.7; p<0.0001). Multivariable regression confirmed that MRI did not decrease the rate of a 7-day return visit (OR=0.98; 95% CI 0.68 to 1.42).

CONCLUSIONS: In patients with uncomplicated back pain, performing an MRI will not mitigate their likelihood of return; however, it leads to a longer ED LOS and more ED observation admissions.