What is the normal CT and MRI appearance of the upper GI tract?
The normal bowel wall is generally ≤3 mm in thickness when well distended. However, the gastric antrum and pylorus may normally measure up to 11 mm, and underdistended portions of normal bowel may also appear to be thicker than 3 mm but without asymmetric thickening or abnormal enhancement. On unenhanced CT and MR images, the wall of the bowel attenuation and signal intensity are similar to those of skeletal muscle. On contrast-enhanced CT and MR images, the bowel wall normally has uniform homogeneous enhancement that is typically less than or similar to that of the liver. However, the normal gastric wall may sometimes have a stratified enhancement pattern, where the mucosal layer (and sometimes the serosal layer) has greater enhancement than the submucosal layer.
The esophagus typically appears underdistended, and the stomach may be variably distended on cross-sectional imaging. The small bowel is generally ≤3 cm in caliber, and the jejunum typically has thicker, taller, and more numerous (4 to 7 per inch) valvulae conniventes (also called folds of Kerckring or plicae circulares) than the ileum (2 to 4 per inch).