Emergency biliary sonography: utility of common bile duct measurement in the diagnosis of cholecystitis and choledocholithiasis.

BACKGROUND Measurement of the common bile duct (CBD) has traditionally been considered an integral part of gallbladder sonography, but accurate identification of the CBD can be difficult for novice sonographers. OBJECTIVE To determine the prevalence of isolated sonographic CBD dilation in emergency department (ED) patients with cholecystitis or choledocholithiasis without laboratory abnormalities or other pathologic findings on biliary ultrasound. METHODS We conducted a retrospective chart review on two separate ED patient cohorts between June 2000 and June 2010. The first cohort comprised all ED patients undergoing a biliary ultrasound and subsequent cholecystectomy for presumed cholecystitis. The second cohort consisted of all ED patients receiving a biliary ultrasound who were ultimately diagnosed with choledocholithiasis. Ultrasound data and contemporaneous laboratory values were collected. Postoperative gallbladder pathology reports and endoscopic retrograde cholangiopancreatography (ERCP) reports were used as the criterion standard for final diagnosis. RESULTS Of 666 cases of cholecystitis, there were 251 (37.7%) with a dilated CBD > 6 mm and only 2 cases (0.3%; 95% confidence interval [CI] 0.0-0.7%) of isolated CBD dilation with an otherwise negative ultrasound and normal laboratory values. Of 111 cases of choledocholithiasis, there were 80 (72.0%) with a dilated CBD and only 1 case (0.9%; 95% CI 0.0-2.7%) with an otherwise negative ultrasound and normal laboratory values. CONCLUSION The prevalence of isolated sonographic CBD dilation in cholecystitis and choledocholithiasis is <1%. Omission of CBD measurement is unlikely to result in missed cholecystitis or choledocholithiasis in the setting of a routine ED evaluation with an otherwise normal ultrasound and normal laboratory values.