Radiology, Vol 177, 167-169, Copyright © 1990 by Radiological Society of North America
Gallstone composition in relation to buoyancy at oral cholecystography
PF Malet, J Baker, MJ Kahn and RD Soloway
Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia.
Although it is recognized that some gallstones float at oral
cholecystography, the reasons for this are not known. To determine how
stone type and composition are related to stone buoyancy, the authors
analyzed gallstones from 90 patients in the National Cooperative Gallstone
Study. Seventeen patients had floating and 73 had nonfloating radiolucent
stones at oral cholecystography. Stone analysis showed that all 17 floating
stones were cholesterol stones; 64 of the nonfloating stones were
cholesterol stones, while nine were pigment stones. The cholesterol
contents of floating and nonfloating cholesterol stones were similar, 90.4%
+/- 1.7 and 87.0% +/- 1.2 of stone weight, respectively. The calcium salt
content of the nonfloating cholesterol stones was 3.2% +/- 0.6, while that
of the floating cholesterol stones was only 1.1% +/- 0.4 (P = .02). The
results indicate that floating gallstones are cholesterol stones with a
significantly lower calcium salt content than that of nonfloating
cholesterol stones.
