The use of additional imaging studies after biliary point-of-care ultrasound in the emergency department

We sought to determine the test characteristics of biliary point-of-care ultrasound (POCUS) and to assess the usefulness of obtaining radiology ultrasound (RUS) or cholescintigraphy (HIDA) after biliary POCUS.

We conducted a retrospective review of emergency department patients who underwent biliary POCUS between May 4, 2018 and November 28, 2021. To be included, patients had to have at least one of the following confirmatory evaluations (considered in this order): surgery, HIDA, RUS, or abdominal CT scan. When a discrepancy existed between the POCUS and the RUS or HIDA, they were compared to a higher criterion standard (if available).

Using 348 patients who had a confirmatory evaluation after biliary POCUS, we found the sensitivity and specificity of biliary POCUS for gallstones to be 97.0% (95% CI 92.6 to 99.2%) and 99.5% (95% CI 97.3 to 100%), respectively. For cholecystitis, the sensitivity and specificity were 83.8% (95% CI 72.9 to 91.6%) and 98.6% (95% CI 96.4 to 99.6%), respectively. RUS and POCUS were concordant in 72 (81.8%) of 88 cases in which the patient had both studies while HIDA and POCUS were concordant in 24 (70.6%) of 34 cases. POCUS was deemed correct in at least 50% of discrepant cases with RUS and at least 30% of discrepant cases with HIDA.

Biliary POCUS has excellent sensitivity and specificity for cholelithiasis; it has lower sensitivity for cholecystitis, but the specificity remains high. Performing a confirmatory RUS or cholescintigraphy after a positive biliary POCUS adds little value, but additional imaging may be useful when POCUS is negative for cholecystitis.