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Anatomical relationship between crural diaphragm and lower oesophageal sphincter: an electrophysiological study

We performed electrophysiological studies in 12 normal, healthy subjects to determine the relative locations of the lower oesophageal sphincter, crural diaphragm and squamocolumnar junction. Oesophagogastric junction pressure, crural diaphragm electromyogram and mucosal potential difference were measured using a specially designed catheter. This catheter had a side hole to measure pressure and electrodes placed around the side hole for crural diaphragm electromyogram recordings. Mucosal potential difference was measured at the side hole that measured pressure. Recordings were obtained using a motorized rapid pullthrough at a constant speed of 0.85 cm/sec. Rapid pullthroughs were performed under the following conditions: (a) end expiration (diaphragm relaxed), (b) during a sustained maximal contraction of the diaphragm, and (c) during 50% of maximal diaphragmatic contraction. Our results show that the lower oesophageal sphincter is 4.4 cm in length, 2 cm of which is located in the abdomen. The crural diaphragm is 1.7 cm in length and surrounds the proximal half of the lower oesophageal sphincter. The squamocolumnar junction is located in the upper half of the lower oesophageal sphincter in the majority of subjects. The relative location of the lower oesophageal sphincter to the crural diaphragm does not change during diaphragmatic contraction. We conclude that a part of the lower oesophageal sphincter is located in the abdomen. The intra‐abdominal location of the lower oesophageal sphincter may be important for its anti‐reflux barrier function.