Abnormalities of the Gastroesophageal Junction (2024)

Cardia

The gastric cardia is often not visualized on single-contrast barium studies because this region is obscured by barium in the fundus or by overlying gastric rugae. However, the ability to recognize the normal appearances of the cardia has improved dramatically with the use of double-contrast technique. In one study, the normal anatomic landmarks at the cardia were seen on more than 95% of double-contrast examinations but on only 20% of single-contrast examinations. Thus, double-contrast technique is essential for evaluating this area.

The radiographic appearance of the cardia on double-contrast studies depends on how firmly it is anchored by the surrounding phrenoesophageal membrane to the esophageal hiatus of the diaphragm. When the cardia is well anchored, protrusion of the distal esophagus into the fundus produces a circular elevation containing three or four stellate folds that radiate to a central point at the gastroesophageal junction, also known as the cardiac rosette ( Fig. 26-1A ). This elevation is demarcated from the adjacent fundus by a curved hooding fold that surrounds it laterally and superiorly. Several longitudinal folds are usually seen extending inferiorly from the cardiac rosette along the posterior wall of the lesser curvature. However, it should be recognized that the cardiac rosette reflects the closed resting state of the lower esophageal sphincter, so this normal anatomic landmark will be transiently obliterated by relaxation of the lower esophageal sphincter during deglutition.

When the cardia is less firmly anchored to the surrounding phrenoesophageal membrane, the cardiac rosette may be visible without an associated protrusion or circular elevation ( Fig. 26-1B ). With further ligamentous laxity, the rosette itself may vanish and the cardia may be characterized by only a single undulant or crescentic line that traverses the region of the esophageal orifice ( Fig. 26-1C ). Finally, severe ligamentous laxity may lead to the formation of an axial hiatal hernia, so no cardiac structure is identified below the diaphragm. Instead, gastric folds may converge superiorly to a point several centimeters above the esophageal hiatus ( Fig. 26-1D ). This finding should therefore suggest an axial hiatal hernia, and a single-contrast esophagogram should be obtained with the patient in a prone position to confirm the presence of a hernia.

Radiologists should be familiar with the various radiographic appearances of the cardia, because malignant tumors involving the cardia may be recognized only by distortion or obliteration of these normal anatomic landmarks (see later, “ Carcinoma of the Cardia ”).

Z Line

The Z line is an irregular serrated line that demarcates the squamocolumnar mucosal junction. The Z line can sometimes be recognized on double-contrast esophagograms as a thin radiolucent stripe in the distal esophagus with a characteristic zigzag appearance ( Fig. 26-2 ). Occasionally, the Z line can be mistaken for superficial ulceration associated with reflux esophagitis, particularly if the esophagus is not completely distended. Because the Z line represents the histologic squamocolumnar junction, it is usually located at or near the gastroesophageal junction.

Mucosal Ring

A lower esophageal mucosal ring is the most common ringlike narrowing found in the distal esophagus. The ring consists of a membranous ridge covered by squamous epithelium superiorly and columnar epithelium inferiorly, so it corresponds histologically to the squamocolumnar junction. This mucosal ring, also known as a B ring, is manifested on barium studies by a thin, weblike area of narrowing at the gastroesophageal junction ( Fig. 26-3 ). The ring has smooth, symmetric margins and a height of 2 to 4 mm. Mucosal rings with a diameter more than 20 mm rarely cause symptoms. If the diameter of the ring is less than 20 mm, however, it may cause dysphagia and might therefore represent a pathologic finding (see later, “ Schatzki Ring ”).

Lower esophageal mucosal rings are fixed, reproducible structures on barium studies, but the distal esophagus must be adequately distended to visualize these structures. Single-contrast technique with the patient in a prone, right anterior oblique position is particularly well suited for demonstrating lower esophageal rings because it is the best technique for achieving optimal distention of the distal esophagus. It has been shown that more than 50% of lower esophageal rings seen on prone single-contrast views of the esophagus are not visualized on the double-contrast phase of the examination. Thus, biphasic studies are required to demonstrate these structures.

Muscular Ring

A muscular or contractile ring, also known as an A ring, is a much less common finding in the distal esophagus than a mucosal ring (B ring). Muscular rings are located at the proximal end of the esophageal vestibule near the tubulovestibular junction and are completely covered by squamous epithelium. Unlike a mucosal ring, which is a fixed anatomic structure, a muscular ring occurs as a transient physiologic phenomenon resulting from active muscular contraction in the distal esophagus in the region of the lower esophageal sphincter.

A muscular ring usually appears on esophagography as a relatively broad, smooth area of tapered narrowing that changes considerably in caliber and configuration during the fluoroscopic examination (see Fig. 26-3 ). Because a muscular ring is caused by active muscular contraction, it may vanish completely with esophageal distention, so it is observed as a transient finding at fluoroscopy. Not infrequently, mucosal and muscular rings are visible during the same examination (see Fig. 26-3 ). In such cases, the fixed nature of the mucosal ring readily distinguishes this structure from the changing appearance of the muscular ring above.