1. A method for monitoring passage of at least one food bolus through the esophagus whereby to evaluate the esophageal function of a patient, comprising the steps: (a) acquiring ultrasonic image data of said at least one bolus at a plurality of temporal intervals as said at least one bolus passes through the esophagus after being swallowed by the patient; (b) tracking said at least one bolus in said image data to identify esophagus and bolus image data corresponding to said bolus and to said esophagus in said image data; (c) determining at least one esophagus function parameter from the said bolus and esophagus image data.