The phrenic ampulla: distal esophagus or potential hiatal hernia?
The mechanics of phrenic ampullary emptying were analyzed to determine whether this structure functions in a manner similar to the tubular esophagus or a hiatal hernia. Simultaneous videofluoroscopy and intraluminal manometry of the gastroesophageal junction were done during barium swallows in 18 normal volunteers. Esophageal emptying was studied without any external influences, during abdominal compression with a cuff inflated to 100 mmHg, during a Müller maneuver, and after medication with atropine. The key finding of the study was that ampullary emptying was distinct from esophageal bolus transport in several ways: the propagation velocity of the clearing wave was slower, the maximal contact pressures achieved after luminal closure were lower and unaffected by atropine or outflow obstruction, and ampulary emptying was driven by a hydrostatic pressure difference between the ampulla and stomach rather than by a peristaltic contraction. Increased bolus volume slightly enlarged the ampulla. Taken together, these findings suggest that ampullary emptying occurs, in part, as a result of the restoration of esophageal length (presumably by tension from the phrenoesophageal membrane) rather than as a result of an aborally propagated contraction. As such, a normal phrenic ampulla is analogous to a small reducing hiatal hernia. We speculate that overt hernia formation occurs as a result of progressive degeneration of the phrenoesophageal membrane.