Normally a balance of bile salts, lecithin and cholesterol keep gallstones from forming. If there are abnormally high levels of bile salts or, more commonly, cholesterol, stones can form. Symptoms usually occur when the stones block one of the biliary ducts or gallstones may be discovered upon routine x-ray or abdominal CT study.
Review Date: 8/11/2011 Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; and George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.