A pharyngeal pouch is an out-pouching or pocket (diverticulum) that develops from the posterior wall of the pharynx just above the entrance to the oesophagus (gullet). The pouch may develop as the result of a lack of co-ordination in timing and muscle tone within the sphincter muscle at the top of the oesophagus (cricopharyngeus muscle) During the act of swallowing, the muscles of the pharynx contract and pressure in the pharynx increases. If the cricopharyngeus muscle does not open at the appropriate time, pressure builds up immediately above it and the pharyngeal mucosa may herniate through a potential weakness in the posterior wall of the pharynx at ‘Killian’s dehiscence’, between the cricopharyngeus and thyropharyngeus muscles. This results in the development of the pouch.
Patients usually present with symptoms in the sixth and seventh decade of life. Symptoms of pharyngeal pouch vary and small pouches may cause no symptoms at all. However, pouches may give rise to difficulty in swallowing, sensation of a lump in the throat or of food sticking in the throat and may eventually lead to troublesome regurgitation of food. Food may enter the pouch rather than passing down the oesophagus and this, in addition to regurgitation, may result in weight loss, hoarseness of voice and/or recurrent chest infections (as a result of food going down the airway). The diagnosis is usually confirmed with a barium swallow examination. It is also important to note that there is a real but low risk of carcinoma developing in a pharyngeal pouch, the quoted incidence being of the order of 0.4% to 1.5%. Therefore untreated pouches do need long-term follow-up.
Symptomatic pharyngeal pouches are generally treated by surgery. There are two main types of procedure: open and endoscopic. In an open procedure the pouch is approached through a neck incision and the pouch is excised (diverticulectomy). The spasm induced by the cricopharyngeus muscle is treated by dividing the muscle fibres of the cricopharyngeus muscle (a cricopharyngeal myotomy).
Nowadays, more commonly, an endoscopic procedure the approach to the pouch is made through the mouth (transorally). The principle objective of the procedure is the division of the separating wall between the pouch and the oesophagus (using a staple cutter) to convert it into one cavity. As the separating wall consists of the cricopharyngeal muscle, a cricopharyngeal myotomy is always carried out during endoscopic division. Endoscopic stapling has become the most frequent surgical intervention for pharyngeal pouch in the United Kingdom. Endoscopic surgery is minimally invasive and associated with shorter operative times, shorter postoperative recovery, quicker resumption of oral intake and, overall, lower complication rates. However, not all patients can be treated endoscopically. The contraindications for the endoscopic approach may be related to size of the pouch (too small/too large) or the difficulty of surgical access due to anatomical constraints.