Oesophageal shortening: in vivo validation of high-frequency ultrasound measurements of oesophageal muscle wall thickness

Background and aims Assessment of oesophageal muscle wall thickness with high-frequency intraluminal ultrasound (HFIUS) is proposed as a method to evaluate longitudinal muscle contraction and oesophageal shortening in patients with oesophageal symptoms. Studies using this technique suggested that prolonged oesophageal wall thickening can be associated with chest pain and heartburn. Validation studies comparing HFIUS measurements against fluoroscopic investigations of oesophageal shortening are not available. The aim of this study was to evaluate the relationship between oesophageal muscle wall thickening and oesophageal shortening in vivo. Methods Oesophageal shortening and muscle wall thickness were assessed simultaneously in lightly sedated cats, using fluoroscopic tracking of endoscopically attached metal clips and HFIUS, respectively. Oesophageal shortening was studied during secondary peristalsis and oesophageal mucosal acidification. Video fluoroscopy and HFIUS images were recorded simultaneously and the magnitude and timing of changes in distance between clips and muscle wall thickness were compared. Results During peristalsis, the distance between the clips was maximally reduced to 33% and the muscle wall thickness was increased to 218% above baseline. Maximal shortening and wall thickening correlated significantly and occurred simultaneously. Likewise, mucosal acidification provoked simultaneous oesophageal shortening (20%) and increased basal muscle wall thickness (40%). Secondary peristalsis during mucosal acidification was associated with strong and prolonged oesophageal shortening. Conclusions Oesophageal muscle wall thickening, measured with HFIUS is a good predictor of oesophageal shortening and longitudinal muscle contraction during swallowing and oesophageal mucosal acidification.