Pressure and abdominal length of the distal esophageal sphincter are important factors in maintaining competency of the cardia against challenges of intraabdominal pressure. Some patients with normal distal esophageal sphincter pressure and position may have reflux which could be due to the inability of the cardia to overcome challenges of intragastric pressure. Three experimental studies and one clinical study were designed to evaluate this problem. The results showed that the resistance to flow through the cardia is related to the integrated effect of distal esophageal sphincter pressure and length; the ratio of distal esophageal sphincter to intragastric pressure necessary to maintain competency is inversely related to the length of sphincter present; gastric dilatation has an adverse effect on the degree of competency achieved by a given distal esophageal sphincter length; and patients with an overall distal esophageal sphincter length of 2 cm or less measured at rest in the fasting state are subject to reflux caused by gastric dilatation, increased intragastric pressure independent of intraabdominal pressure, or both.
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