Relationship between esophageal muscle thickness and intraluminal pressure: an ultrasonographic study

A number of studies show a close temporal relationship between the rate of change in muscle thickness as detected by high-frequency intraluminal ultra sonography (HFIUS) and intraluminal pressure measured by manometry. There i s a marked variability in esophageal contraction amplitude from one swallow to another at a given level in the esophagus and along the length of the e sophagus. Furthermore, peristaltic pressures are higher in the distal compa red with the proximal esophagus. The goal of this study was to evaluate the relationship between the baseline and peak muscle thickness and the contra ction amplitude during swallow-induced contractions along the length of the esophagus. Fifteen normal subjects were studied using simultaneous esophag eal pressures and HFIUS or HFIUS alone. Recordings were made during baselin e and standardized swallows in the lower esophageal sphincter (LES) and at 2, 4, 6, 8, and 10 cm above the LES. HFIUS images were digitized, and esoph ageal muscle thickness and peak contraction amplitudes were measured. In th e resting state, muscle thickness is higher in the LES compared with the re st of the esophagus. Baseline muscle thickness is also significantly higher at 2 cm vs. 10 cm above the LES. In a given subject and among different su bjects, there is a good relationship between peak muscle thickness and peak peristaltic pressures (r = 0.55) at all sites along the length of the esop hagus. The positive correlation between pressure and muscle thickness impli es that the mean circumferential wall stress is fairly uniform from one swa llow to another, irrespective of the contraction amplitude.