79 Pharyngeal Pouch
The term pharyngeal pouch refers to a pseudo-diverticulum of the pharyngeal wall. Pharyngeal pouches are uncommon, with an incidence of approximately 1 case per 100,000 population per year. Zenker’s diverticula are located superior to cricopharyngeus and are the most common pharyngeal pouch. An oesophagoscopy should be performed prior to treatment as rarely a squamous cell carcinoma can develop in the lining of the pouch. Rigid endoscopic stapling is the treatment of choice in most units. Patients must be fully informed of the risks of perforation which may necessitate an open procedure to close the perforation.
79.1 Aetiology and Pathogenesis
The precise mechanism for the development of pharyngeal pouches is not known. The current understanding is that pharyngeal pouches develop due to high intra-luminal pressure within the pharynx as a result of incoordination of swallowing. The pharyngeal wall then herniates through a weak area of the pharynx. As the diverticula involve only the submucosa and mucosa, and not the muscle, they are more correctly classified as pseudodiverticula. Zenker’s diverticula are the most common of the pharyngeal pouches. These arise posteriorly by herniation of the pharyngeal mucosa through a relatively weak part of the posterior pharyngeal wall bounded by thyropharyngeus superiorly and cricopharyngeus inferiorly. Other types of pharyngeal pouches are Killian’s diverticula, which arise inferior to cricopharyngeus laterally, and Laimer’s diverticula, which arise inferior to cricopharyngeus in the posterior midline. Once a pouch is formed, food enters it and stretches it further, so that it enlarges. When the pouch reaches a moderate size, food may enter it preferentially. Pressure from the pouch may then be exerted on the oesophagus to cause dysphagia.
79.2 Staging
Various ways of staging pharyngeal pouches have been suggested over the years. Lahey (1930) described stages depending on the shape of the pouch seen on contrast radiography. Brombart (1964) described changes seen on contraction of the upper oesophageal sphincter, Morton (1993) classified stages on direct measurement of pouch size and van Overbeek (1994) classified stages depending on the number of vertebral bodies counted beside the pouch.
79.3 Clinical Features
Pharyngeal pouches are most frequently seen in the elderly. Presenting symptoms include a sensation of a lump in the throat, dysphagia, regurgitation of undigested food, halitosis, weight loss, chronic cough and recurrent chest infections due to aspiration. Hoarseness may occur as a result of irritation of the vocal cords from repeated aspiration. Swelling in the neck may be present which may gurgle on palpation (Boyce’s sign) and empty on external pressure. Rarely, a pouch may have an invasive squamous cell carcinoma in its wall.
79.4 Diagnosis
Pharyngeal pouches are sometimes diagnosed incidentally during flexible oesophagogastroduodenoscopy (OGD). In these cases, it may be difficult to advance the flexible endoscope past the pharyngeal pouch and into the oesophagus. The definitive investigation is a barium swallow, which demonstrates the pouch.
Oesophagoscopy should be carried out to exclude the presence of carcinoma. The instrument usually enters the pouch and a septum may be seen anteriorly separating it from the oesophagus.
79.5 Management
No treatment
Pharyngeal pouches that are asymptomatic do not require treatment.
79.5.1 Endoscopic Techniques
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