[Sonography of gallbladder calculi: possibilities and limits in the selection of gallstone patients suitable for conservative lysis].

The sonographic patterns of artificially produced pure cholesterol and pigment gallstones were evaluated in vitro. Cholesterol calculi exhibited a smooth echo with a relatively high beam penetration, whereas pigment calculi showed a sickle-like surface echo without beam penetration. Clinical evaluation of these criteria in 107 patients was based on correlating preoperative sonographic diagnosis with postoperative microchemical analysis of the calculi. Although small, smooth cholesterol calculi were detected via ultrasound with an accuracy of more than 90 percent, pigment calculi could not be separated and identified with satisfactory precision.