The degrees of gastric barium excretion based on the tip of barium flow in a single-contrast frontal view of the stomach in the standing position. (A) V type (in the stomach). (B) V-H type (in the proximal half of the duodenal bulb). (C) H-V type (in the distal half of the duodenal bulb). (D) H type (in the descending part of the duodenum).