Gallstone Ileus : Introduction
INTRODUCTION: Gallstone ileus refers to intestinal obstruction caused by impaction of a large gallstone within the bowel lumen. It accounts for 1% to 4% of all cases of intestinal obstruction. The term gallstone ileus is a misnomer because it represents a true mechanical obstruction of the intestine by one or more gallstones rather than a defect in motility.
PATHOGENESIS: This complication of cholelithiasis is more common in older women (7th or 8th decade of life). The presence of a large stone (> 2.5 cm) causes gradual erosion of the gall bladder fundus leading to the formation of cholecystoenteric fistula in the duodenum (most common) or colon (rare). Once a passage is created, the stone passes down the length of the intestine causing intermittent obstruction until it is finally impacted where the lumen is narrowest. The most common sites are terminal ileum (60%), jejunum (15%), and colon (5%). A normal caliber bowel (i.e. without stricture) requires at least 2 cm or larger stone to cause obstruction. In some cases, the gallstone propagates proximally and causes gastric outlet obstruction by getting impacted at the pylorus (Bouveret's syndrome).
IMAGING STUDIES:: The classic radiologic findings are: pneumobilia (air in biliary tract), intestinal obstruction (dilated loops of small intestine), aberrant gallstone location (Rigler's triad), and a changing location of the gallstone on subsequent imaging studies. Only about 10% of gallstones have sufficient calcium to be visible on abdominal plain films. This CT pelvis shows 3 large stones within loops of ileum. For detailed case history, see next image.
Case courtesy of: Dr. Sanjay D. Deshmukh (Professor of Pathology), Dr. Jayant M. Gadekar (Chief of Surgery), and Dr. Priyanka Ingole (Senior Resident in Pathology), Dr. Vithalrao Vikhe Patil Foundation's Medical College and Hospitals, Ahmednagar, India.