Protusion of the oesophagal wall as a result of localized weakness in the muscular layer, occurring almost anywhere in the oesophagus, but usually in the upper section, causing the most discomfort. A so-called Zenker’s diverticulum forms a pear-shaped swelling just above the entrance to the oesophagus; the swelling can become so large that it can be felt from the outside at the left of the neck. Pieces of food accumulate in the sac. Diverticulum of the oesophagus causes problems in swallowing because of the pressure of the sac on the oesophagus. Immediately after a meal food can be regurgitated from the sac, enter the air passages, and cause coughing fits. Another symptom is mouth odour because of the presence of half-digested food near the throat. The diverticulum shows on a contrast X-ray.