228 THE LARYNX, BRONCHI AND OESOPHAGUS to pressure. This is reinforced if the cricopharyngeus stays closed longer than usual, or if it has a high state of tonus. Gradually the area expands and soon forms a pouch. Food collects in this small pouch thus stretching it more and enlarging it. When the pouch gets to a certain size it lies in line with the oesophagus and becomes the natural opening for food (and oesophagoscopes!) to enter. This further increases its size and causes it to expand and to press on the oesophagus when full of food, causing dysphagia. SYMPTOMS. Even when the pouch is small there will be a feeling of a lump in the throat. As the pouch enlarges true dysphagia will follow. When the pouch fills with food during a meal there will come a point when it overflows into the pharynx causing regurgitation of undigested food. Some may overflow into the larynx resulting in coughing fits. A barium swallow will confirm the diagnosis (Fig. 116). Fig. 116. Radiograph to show a pharyngeal pouch. TREATMENT. The most satisfactory treatment of a pouch is to remove it. This is done by making a collar incision on the left side of the neck, retracting the carotid sheath laterally and the laryngopharynx medially, identifying the pouch (which can be made easier by packing it with acriflavine prior to surgery), dividing the neck of the pouch and suturing the opening in layers. If too much is removed there is a danger of stenosis, but if not enough is removed the pouch will recur. An alternative method exists of using diathermy coagulation of the common wall between the pouch and the oesophagus (Dohlman's operation). This is a simpler and quicker method than excision, but in inexpert hands it can lead to mediastinitis from perforation and damage to the recurrent laryngeal nerves by diathermy. The procedure is done endoscopically using a specially designed oesophagoscope with two beaks—one for the oesophagus and one for the pooch. The stretched wall between the two is clamped and diathermied, again using specially designed instruments.