349 Comparison of Common Bile Duct Measurement by Point-of-Care Ultrasound to Radiology-Performed Ultrasound

Abstract

Exact incidence of common bile duct (CBD) stones is not known, but they have been found in 10-18% of patients undergoing cholecystectomies. They are associated with significant morbidity, resulting in pancreatitis or cholangitis if left untreated. Unfortunately, physical exam and lab tests are unreliable in detecting CBD stones. Limited data exists evaluating the use of point-of-care ultrasound (POCUS) in the emergency department (ED) to evaluate for CBD stones. Our objective was to evaluate the accuracy of CBD diameter measured on POCUS compared to radiology-performed ultrasound. In this retrospective chart review of one academic medical institution, we analyzed 4.5 years of POCUS data to find all cases where CBD dilation was measured and documented by an emergency physician in a POCUS report. We compared these results to radiology-performed ultrasound results of those same patients and compared the two values using paired Student’s T-test to test for significance, mean absolute error (MAE), and Pearson’s correlation coefficient. A total of 126 potential cases of CBD dilation were identified based on POCUS reports that had CBD dilation recorded. Of these, 53 (42%) had radiology imaging studies performed. Thirty-nine (74%) of those included were female. The mean CBD diameter measured on POCUS was 7.61mm (range: 1.3-16.8mm). The mean CBD diameter measured on formal radiology studies for these same patients was 7.34mm (range: 1.0-16.0mm). The two means were not significantly different by paired Student’s T-test (p = 0.63). However, mean absolute error between the two samples was 2.73mm. Pearson’s correlation coefficient was 0.27 (with +1/-1 indicating perfect correlation). While there was not a significant difference between the two samples’ means, there was poor agreement between POCUS and formal radiology US in the evaluation of CBD diameter. We cannot conclude that the two modalities are equivalent in their ability to accurately measure CBD diameter at this time. Limitations of this study include: retrospective chart review with small sample size and no standardization in the qualifications of the physicians performing the POCUS. Future work should include prospective cases and explore how ED providers who receive standardized POCUS training perform versus radiology-performed US for the measurement of CBD diameter.