Esophageal Rings

The A-ring is a muscular ring that results from transient muscular contractions. It is a smooth, broad narrowing that is rarely symptomatic.

The B-ring is a thin mucosal ring at the esophagogastric junction. It is smooth and symmetric. Patients usually present with symptoms when the luminal diameter is less than 13 mm, at which point the B-ring is called a Schatzki ring.

The Z-line is the squamocolumnar junction that is normally near the B-line, but doesn't necessarily correspond to the B-line. It can move proximally in cases of Barrett esophagus. When seen (rare), it is a thin serrated line.

The C-ring is the indentation of the esophagus by the diaphragmatic crura.