Utility of Common Bile Duct Identification on Biliary Ultrasound in Emergency Department Patients

Background: Biliary ultrasound is often utilized in the evaluation of abdominal pain in the Emergency Department (ED). Common bile duct (CBD) identification is traditionally a standard component of the biliary ultrasound examination but can be challenging to perform for the novice sonographer. Previous work has demonstrated that CBD dilatation is rare in cases of cholecystitis with normal liver function tests (LFTs). We sought to assess the frequency of CBD dilatation in the subset of ED patients undergoing hepatobiliary ultrasound who have normal LFTs and an absence of gallstones or biliary sludge on ultrasound. We also performed an assessment of changes in CBD diameter by age and cholecystectomy status. Methods: This was a retrospective chart review at a single academic ED. Patients were enrolled in the study if they underwent a radiology performed (RP) hepatobiliary ultrasound within the 2 year study period. Records were reviewed for the presence of gallstones or sludge, CBD diameter, age, clinical indication for the ultrasound, and LFTs. Descriptive analyses were performed, and interobserver agreement among data abstractors was assessed by K analysis for the presence of CBD dilatation. The Mann-Whitney test was utilized to assess statistical significance in the comparison of differences between CBD diameters amongst age groups. Results: Of 1929 RP hepatobiliary ultrasounds performed in the study period, 312 were excluded and 1617 met inclusion criteria. Amongst these, there were 506 patients who had normal LFTs and an ultrasound with no stones or sludge. Ten patients within this group had a dilated CBD > 7 mm (1.98%, 95% CI of 1.08% to 3.6%). We also noted a statistically significant increase in CBD size in the older age cohort and in those individuals with a history of cholecystectomy. Conclusion: CBD dilation in ED patients who present with normal LFTs and an absence of gallstones and biliary sludge is rare. Physicians should be reassured that the routine identification of the CBD on ultrasound in this setting is of low yield and need not be pursued.