Value of prone positioning in the ultrasonographic diagnosis of gallstones: prospective study.

To determine prospectively the value of prone/postprone positioning in the sonographic detection of gallstones, 682 patients were scanned in the recumbent, erect, and prone or postprone positions. The gallbladder was evaluated for an intraluminal hyperechoic focus, shadowing, and gravitational dependence and was identified in 679 patients. Among these, 28% had cholelithiasis. In five cases, prone positioning alone revealed gallstones. In 11 of 140 cases, gravitational dependence was only seen with prone scanning. The gallbladder was seen more frequently when the patients were prone than erect. Prone or postprone scanning is a useful supplement to the gallbladder examination, allowing increased demonstration of gravitational dependence and increased stone detection.