This document outlines various disorders that can affect the preoesophageal, oral, and pharyngeal phases of swallowing, as well as the lumen, wall, and outside of the esophagus. It discusses diagnostic tests and investigations for esophageal disorders, including blood tests, radiography, manometry and pH studies, and oesophagoscopy. Manometry and pH studies help evaluate motility disorders, gastroesophageal reflux, and determine if esophageal spasms are spontaneous or acid-induced.