Figure 4 - Radiograph of a patient with a small axial hiatal hernia (case 1).

A well-developed A ring is evident, but no B ring. In such cases the criterion for defining hiatus hernia is the appearance of rugal folds traversing the diaphragmatic hiatus. The A ring has no anatomic correlate but physiologically corresponds to the superior aspect of the LES. (Source: Kahrilas and Pandolfino,⁷⁵ with permission.)