THE INFERIOR ESOPHAGEAL SPHINCTER, THE MANOMETRIC HIGH PRESSURE ZONE AND HIATAL INCOMPETENCE

¹ From the Department of Radiology and the Division of Gastroenterology, The Mount Sinai School of Medicine and Hospital, New York, New York

The normal sphincteric mechanism in the esophagogastric region is represented by a zone of resting pressure greater than fundic pressure—the manometric high pressure zone or HPZ. The HPZ is about 3 cm. in length, begins about 1 cm. above the hiatus and extends to the cardiac orifice. Pressure in this zone decreases prior to the arrival of a bolus. Anatomically this zone includes the collapsed vestibule and cardiac canal. The vestibule is demarcated distally by the squamocolumnar junction or constrictor cardiae fibers, and proximally by a potential contractile or A ring about 2 cm. above the mucosal

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junction in the filled state. The cardiac canal extends from the vestibule to the cardiac orifice or cardiac rosette. This canal is gastric-lined and enclosed by the sling fibers continuous with the inner oblique muscle layer of the stomach. With progressive stretching of the phrenicoesophageal membrane and widening of the hiatus, the HPZ diminishes or disappears (hiatal incompetence). The sling fibers fail to contract completely so that the cardiac canal becomes part of the fundus of the stomach. The normal cardiac incisura and orifice are effaced resulting in shortening or obliteration of the normal roentgenologic submerged segment. The vestibule fills and empties normally but does not maintain normally elevated pressure in the resting phase. These changes are progressive and lead finally to free reflux (chalasia) because no functional or mechanical anti-reflux mechanism remains. However, reflux may be prevented by the appearance of a prominent persistent A ring which may act as a short sphincteric zone of resting elevated pressure at the proximal margin of the vestibule. Local resting pressure at the site of an A ring may equal or exceed the peak pressure of the normal HPZ. A prominent A ring is usualls designated the "inferior esophageal sphincter" in accordance with Lerche's original anatomic descriptions. However, if this term is to be used, it must not be equated with the normal esophagogastric sphincteric mechanism or HPZ. Prominent persistent A

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rings are also seen in other functional abnormualities of the esophagus regularly in diffuse esopiuageal spasm and occasionally in achalasia. An A ring which fails to relax or distend may occasionally cause severe dysphagia without associated functional abnormality of the body of the esophagus. However, the usual A ring associated with a sliding hernia is rarely tiue cause of severe dysphagia and does not require myotomy at the time of hernia repair.

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