Ultrasonic pseudocalculus effect in psotcholecystectomy patients.

Nonvisualization of the gallbladder in ultrasonic cholecystography is noted in 15%--25% of patients with proven cholelithiasis. In this setting, the ultrasonic diagnosis of cholelithiasis and choledocholithiasis is made by detection of strong echoes with distal acoustic shadowing (calculus pattern). A similar pattern was detected in 17 of 26 postcholecystectomy patients, only one of whom had retained bile duct calculi. In the absence of surgical clips in the right upper abdomen (60% in our series), it is assumed that this ultrasonic pseudocalculus effect is caused by postoperative scar at the site of the gallbladder bed. Our data indicate that ultrasonic diagnosis of retained bile duct calculi in postcholecystectomy patients should be made with extreme caution.