To evaluate the morphology, motion and pressure profile of the UES using simultaneous HREUS and manometry.

The UES was evaluated in seven normal subjects and four human cadavers using a 20MHz ultrasound transducer (Olympus, Tokyo) attached to a manometry probe. The morphology of the UES and its surrounding structures were evaluated in normal subjects. The cross-sectional area (CSA), width, angle of the UES musculature and the peak pressure were measured from ultrasound images and pressure profiles. Four fresh human cadavers, who died of diseases unrelated to the GI tract, were studied using the same methodology as in normal subjects.

The UES musculature (cricopharyngeus) appears as a hypoechoic C-shaped structure surrounding the mucosa and submucosa, which forms an angle of 107 ± 19°. The high-pressure zone in the proximal esophagus was always associated with this hypoechoic C shaped structure. Between the UES musculature and the cricoid cartilage, the two posterior cricoarytenoid muscles were seen as hypoechoic oval structures adjacent to the posterior aspect of the cricoid cartilage. The mean peak UES pressure was 74 mmHg above the upper esophageal body pressure with a total CSA of 0.87 ± 0.33 cm2. The UES musculature CSA is significantly greater than total muscular CSA of the upper esophageal body (P=0.01) at rest. During swallowing a simultaneous drop in pressure, with the appearance of upper esophageal body morphology, was observed on ultrasound. Following swallowing, pressure increased in synchrony with the appearance of the UES. The anatomy and morphology of the UES remained the same in the cadavers as in the normal volunteer and the peak pressure recorded in the area of the UES in the cadavers was a mean of 19.7 mmHg over baseline esophageal body pressures.

The ultrasonographic anatomic features of the UES were defined in this study. The UES has greater muscular CSA and resting pressure than the upper esophageal body at rest. The UES elevates in an orad direction during swallowing. The cadaver study suggests that passive mechanical conformational changes contribute to the UES pressure profile.