The key steps are: 1. Identify the gastro-esophageal (GE) junction at the top of the gastric mucosal folds. 2. If hiatus hernia is present, do not confuse the diaphragmatic hiatal impression for the GE junction. 3. For circumferential columnar-appearing mucosa above the GE junction, define the extent in centimeters above the GE junction – report as the C value. 4. For any tongue-like areas of columnar-appearing mucosa, measure the maximum extent, in centimeters, above the GE junction – report as the M value. UI, upper inscisor.