0016-5107/92/3805-0541$03.00 GASTROINTESTINAL ENDOSCOPY Copyright © 1992 by the American Society for Gastrointestinal Endoscopy
Mechanical lithotripsy of large gallstones: correlation with CT characteristics John S. Halsey, MD, Jan Wolak, PhD (Eng) Scott J. Schulte, MD, Richard L. Baron, MD Bryan D. Yates, MD, Michael B. Kimmey, MD Seattle, Washington and Pittsburgh, Pennsylvania
The CT characteristics of gallstones were correlated with mechanical forces required to fragment calculi in vitro. Forty-two gallstones ~11 mm in largest diameter were subjected to in vitro CT scanning and categorized as isodense, faint, laminated, rimmed, or dense as compared with saline. A mechanical lithotripter, attached to a dynamometer, was utilized simulating in vivo technique to accomplish lithotripsy. Significantly more force was required to fracture CTdense (p < 0.02) and CT-rimmed (p < 0.05) gallstones than was required to fracture CT-isodense gallstones. (Gastrointest Endosc 1992;38:541-544)
Endoscopic sphincterotomy with common bile duct stone extraction is successful in eliminating about 90% of common bile duct stones. l Success is less likely when stones are very large, are in intrahepatic ducts, or are located above an anatomical abnormality such as a common bile duct stricture. Several methods have been developed to facilitate stone elimination in these situations. The objective of the techniques is to reduce stone size and thereby allow fragment removal without surgical intervention. Mechanical lithotripsy, extracorporeal shock wave lithotripsy, endoscopic laser fragmentation, electrohydraulic lithotripsy, and chemical dissolution have all been investigated. The success of each therapy is dependent on appropriate patient selection. Commercially available mechanical lithotripsy baskets applied to large common duct stones have met with success varying inversely with stone diameter. 2 ,3 Specific criteria to assist in determining the probability of successful fragmentation with mechanical lithotripsy have not been published. CT of gallstones has previously been utilized to predict gallstone composition and to predict in vitro dissolution with methyl tert-butyl ether. 4- 6 This study was undertaken to determine whether the force required to fracture a gallReceived October 3, 1991. For revision February 10, 1992. Accepted May 7,1992. From the Departments of Medicine, Mechanical Engineering, and Radiology, University of Washington, Seattle, Washington and Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania. Reprint requests: Michael B. Kimmey, MD, University of Washington, RG24, Seattle, Washington 98195. VOLUME 38, NO.5, 1992
stone with a mechanical lithotripter in vitro can be predicted by the CT characteristics of the stone.
METHODS CT Analysis
Forty-two gallstones, 11 mm or greater in largest diameter, were obtained from 19 otherwise unselected surgical specimens. Thirty-five of the stones were stored in saline, one was stored dry, and the precise storage of six stones was unknown. In vitro CT examinations were performed with the stones suspended in saline in a Plexiglas body phantom on a GE 9800 scanner. Gallstones were categorized as described by Baron et a1. 4 and tabulated in Table 1. For each stone appearing homogeneous on CT scan, attenuation values were measured using a representative region.
Lithotripsy
Each stone was blotted dry, weighed, and the largest diameter, smallest diameter, and displacement volume measured. A mechanicallithotripter (Olympus BML-3; Olympus Corporation of America, Lake Success, N. Y.) attached to a dynamometer was used simulating the in vivo technique to fracture each stone (Fig. 1). The following were recorded: force required to initiate stone fragmentation; force required to reduce the largest stone fragment to
Mechanical lithotripsy of large gallstones: correlation with CT characteristics John S. Halsey, MD, Jan Wolak, PhD (Eng) Scott J. Schulte, MD, Richard L. Baron, MD Bryan D. Yates, MD, Michael B. Kimmey, MD Seattle, Washington and Pittsburgh, Pennsylvania
The CT characteristics of gallstones were correlated with mechanical forces required to fragment calculi in vitro. Forty-two gallstones ~11 mm in largest diameter were subjected to in vitro CT scanning and categorized as isodense, faint, laminated, rimmed, or dense as compared with saline. A mechanical lithotripter, attached to a dynamometer, was utilized simulating in vivo technique to accomplish lithotripsy. Significantly more force was required to fracture CTdense (p < 0.02) and CT-rimmed (p < 0.05) gallstones than was required to fracture CT-isodense gallstones. (Gastrointest Endosc 1992;38:541-544)
Endoscopic sphincterotomy with common bile duct stone extraction is successful in eliminating about 90% of common bile duct stones. l Success is less likely when stones are very large, are in intrahepatic ducts, or are located above an anatomical abnormality such as a common bile duct stricture. Several methods have been developed to facilitate stone elimination in these situations. The objective of the techniques is to reduce stone size and thereby allow fragment removal without surgical intervention. Mechanical lithotripsy, extracorporeal shock wave lithotripsy, endoscopic laser fragmentation, electrohydraulic lithotripsy, and chemical dissolution have all been investigated. The success of each therapy is dependent on appropriate patient selection. Commercially available mechanical lithotripsy baskets applied to large common duct stones have met with success varying inversely with stone diameter. 2 ,3 Specific criteria to assist in determining the probability of successful fragmentation with mechanical lithotripsy have not been published. CT of gallstones has previously been utilized to predict gallstone composition and to predict in vitro dissolution with methyl tert-butyl ether. 4- 6 This study was undertaken to determine whether the force required to fracture a gallReceived October 3, 1991. For revision February 10, 1992. Accepted May 7,1992. From the Departments of Medicine, Mechanical Engineering, and Radiology, University of Washington, Seattle, Washington and Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania. Reprint requests: Michael B. Kimmey, MD, University of Washington, RG24, Seattle, Washington 98195. VOLUME 38, NO.5, 1992
stone with a mechanical lithotripter in vitro can be predicted by the CT characteristics of the stone.
METHODS CT Analysis
Forty-two gallstones, 11 mm or greater in largest diameter, were obtained from 19 otherwise unselected surgical specimens. Thirty-five of the stones were stored in saline, one was stored dry, and the precise storage of six stones was unknown. In vitro CT examinations were performed with the stones suspended in saline in a Plexiglas body phantom on a GE 9800 scanner. Gallstones were categorized as described by Baron et a1. 4 and tabulated in Table 1. For each stone appearing homogeneous on CT scan, attenuation values were measured using a representative region.
Lithotripsy
Each stone was blotted dry, weighed, and the largest diameter, smallest diameter, and displacement volume measured. A mechanicallithotripter (Olympus BML-3; Olympus Corporation of America, Lake Success, N. Y.) attached to a dynamometer was used simulating the in vivo technique to fracture each stone (Fig. 1). The following were recorded: force required to initiate stone fragmentation; force required to reduce the largest stone fragment to
