MRI manifestations of gastrointestinal wall thickening.

The appearance of gastrointestinal wall thickening of various entities is demonstrated on magnetic resonance imaging (MRI). The entities include benign gastric ulcer, gastric carcinoma, pancreatic carcinoma with direct invasion of stomach, duodenal leiomyoma, radiation enteritis, peritonitis, colonic carcinoma, recurrent carcinoma at the gastrojejunal anastomosis with direct extension to the transverse colon, colocolic intussusception, sigmoid diverticulitis with pericolonic abscess and fistula into the urinary bladder, and lymphoma of the stomach, duodenum, small bowel, and colon. Air was introduced antegradedly or retrogradedly into the alimentary tract to act as a contrast agent. When the bowel was distended by air, the normal bowel wall was barely visible or even invisible. Abnormal focal or segmental wall thickening was outlined between the intraluminal air and extraluminal fat. In some instances, the thickenings were better demonstrated on coronal or sagittal sections. The proper muscular layer of the bowel has a low-signal intensity and was delineated between the thickened mucosa-submucosa and extramural fat. Interruption of this low-intensity zone might represent tumor invasion through the muscular layer.