Figure 3 - Anatomic features of a sliding hiatus hernia viewed radiographically during swallowing.

The A ring is a muscular ring visible during swallowing that demarcates the superior margin of the LES. The B ring at the squamocolumnar junction is present in only about 15% of individuals and allows for accurate division of the phrenic ampulla into the esophageal vestibule (A ring to B ring) and the sliding hiatus hernia (B ring to the subdiaphragmatic stomach). By convention the distinction between normal and hiatus hernia is a 2-cm separation between the B ring and the hiatus. Rugal folds traversing the hiatus support the conviction that a portion of the stomach is supradiaphragmatic. (Source: Kahrilas,²⁴ with permission from Blackwell Publishing.)