Endoscopic Diagnosis and Management of Zenker’s Diverticula

Introduction

Zenker's diverticulum (ZD) is a posterior pharyngoesophageal mucosal outpouching that forms through Killian's triangle. Poor upper esophageal sphincter (UES) compliance is the acknowledged pathophysiologic mechanism of action, leading to creation of a high-pressure zone, ultimately resulting in diverticulum formation. This entity most commonly presents in the elderly, and can be associated with a plethora of potential symptoms, most commonly dysphagia. Cricopharyngeal myotomy is usually performed alone or in combination with diverticulectomy (when open surgery is performed) to improve symptoms and prevent recurrence.

Clinical Presentation and Diagnosis

ZD most frequently occurs between the seventh and eighth decades of life, predominantly in men. ZD is rarely identified before the age of 40 years. The overall prevalence in the general population is between 0.01% and 0.11%, and varies markedly throughout the world. However, these data reflect symptomatic patients, and the number of asymptomatic patients with ZD remains unknown. Anatomical differences or life expectancy may account for the varying prevalence between geographic areas. In the United Kingdom, the incidence of ZD is approximately 2 per 100,000 people per year. It has been described more commonly in the United States, Canada, and Australia than in Japan and Indonesia. Symptoms may be present for weeks to years before diagnosis. Cervical borborygmus, in the presence of a palpable lump in the neck, is nearly pathognomonic for ZD. Although a multitude of symptoms have been attributed to ZD, 80–90% of patients suffer from dysphagia. Dysphagia occurs secondary to incomplete opening of the UES and extrinsic compression of the cervical esophagus by the diverticulum itself. As the pouch enlarges and dysphagia increases, symptoms often worsen, leading to resultant weight loss and malnutrition. A sudden increase in symptom severity and/or the development of alarming symptoms such as local pain, hemoptysis, or hematemesis may signal the presence of ulceration or squamous cell carcinoma within the diverticulum. Squamous cell carcinoma arising in a ZD is said to have an incidence of 0.4–1.5%, though these older data might reflect more long-standing, untreated disease. Presumably, therapy decreases stasis and risk of cancer. Additional symptoms such as hoarseness/dysphonia, regurgitation, halitosis, cough, and aspiration pneumonia have been described in 30–40% of patients. It is unclear if pneumonia occurs due to direct aspiration of diverticular contents or aspiration of contents pooled within the pharynx. Medications (i.e., capsules, tablets) can become entrapped in the diverticulum, leading to decreased efficacy and, potentially, ulceration with bleeding. Entrapment of a video capsule within a ZD has also been reported. Gastrointestinal bleeding within the diverticulum can occur, and is amenable to endoscopic management.

A variety of other conditions have been associated with ZD. These include laryngocele, leiomyoma, polymyositis, cervical esophageal web, carotid body tumor, postanterior cervical discectomy and fusion, upper esophageal stenosis, hiatal hernia, and gastroesophageal reflux disease.

Pathophysiology

The UES is composed of the posterior surface of the thyroid and cricoid cartilage, as well as three muscles: the inferior pharyngeal constrictor, cricopharyngeus (CP), and cervical esophagus. Of these three muscles, the CP provides for the dominant portion of UES function. It forms a muscular sling around the upper esophagus between the two sides of the cricoid cartilage and extends posteriorly to mesh with the inferior pharyngeal constrictor. Two sets of CP muscle fibers have been identified: the horizontally oriented fibers that occlude the esophageal introitus, and an oblique band of fibers that are responsible for propulsion of the bolus.

The inciting pathophysiologic mechanism of ZD is inadequate UES sphincter compliance with failure to open completely. This failure to achieve adequate diameter for effective bolus clearance leads to increased intraluminal pressure with outpouching in an area of relative wall weakness in the hypopharynx between the CP and inferior pharyngeal constrictor. This area, known as Killian’s Triangle, is adjacent to the retropharyngeal space and thus leads to pouch formation posteriorly ( Fig. 20.1 ). The diverticulum may be posterior, posterolateral, or lateral (pharyngocele), but the most common subtype is the posterior pulsion diverticulum. ZD most commonly forms posteriorly on the left side. This is important for determination of the neck incision site during an open surgical approach and when performing endoluminal therapy, as division of the common wall between the diverticulum and the esophageal lumen is necessary for complete symptom relief. It should be noted that this posterior pouch includes only mucosa and submucosa; therefore a ZD should be considered a “pseudo-diverticulum.” Several other factors may contribute to pharyngoesophageal pouch formation. For example, increased intrabolus pressures have been well documented, and likely occur due to stiffness of the CP and hypopharynx. Increased intrabolus pressure is also increased in older patients who perform multiple swallows to achieve bolus clearance. Moreover, as the diverticulum enlarges, it may compress the pharyngoesophageal segment and lead to increased intrabolus pressure secondary to extrinsic compression. Finally, incoordination of pharyngeal contraction and UES opening has also been variably demonstrated by some investigators. Video fluoroscopy is a valuable tool, particularly for diagnosis, but precise determination of abnormal function is limited by variation in interpretation and quality. Furthermore, useful manometric data are exceedingly difficult to obtain in this area, due to asymmetry in sphincter pressures and wide variations in sphincter motility during swallowing.