Zenker Diverticulum

Introduction

Esophageal diverticula are classified on the basis of anatomic location—pharyngoesophageal, midesophageal, or epiphrenic—and by mechanism of origin, either traction or pulsion. Traction diverticula are a result of pulling forces external to the esophagus secondary to inflammatory or neoplastic processes, such as may be seen after anterior spinal surgery with placement of stabilizing hardware. In contrast, pulsion diverticula are a result of herniation of esophageal mucosa and submucosa through an area of weakened esophageal musculature. Of the various types of esophageal diverticula, Zenker diverticulum (ZD), a pulsion-type diverticulum, is one of the most common symptomatic esophageal diverticula, with an annual incidence of 2 per 100,000 people, with men being affected two to three times more commonly than women. For patients referred for an examination of the upper gastrointestinal (GI) tract, the incidence can reach 1 in 1000. Most esophageal diverticula are acquired lesions found in adults, most commonly in the seventh and eighth decades.

Zenker diverticulum is classically defined as a pulsion diverticulum present between the cricopharyngeal muscle and inferior constrictor muscle in an area of weakness called the Killian dehiscence or Killian triangle, first described by Killian in 1907. However, there are other areas of weakness where pulsion diverticula may form, including the Killian-Jamieson area, between the oblique and transverse fibers of the cricopharyngeal muscle, and the Laimer triangle, formed between the cricopharyngeal muscle and the most superior esophageal wall circular muscles ( Fig. 70.1 ). More rarely, pharyngoceles may be found in the posterolateral or lateral areas of the pharynx and hypopharynx ( Fig. 70.2 ). Cases of double pharyngeal pouches have also been described.

Theoretically, a diverticulum herniates to the side of less resistance. Accordingly, it is hypothesized that ZD is more prone to herniate to the left, because the carotid artery is more laterally located on this side of the neck, making it less adherent to the adjacent prevertebral fascia, and because the cervical esophagus has a slight convexity to the left. According to one series, although two-thirds of Zenker diverticula are found in the midline, nearly 25% protrude to the left, and only 10% protrude to the right.

Presentation

Patient history alone may raise suspicion for ZD. The predominant symptom is progressive dysphagia, which may occur in more than 90% of patients with the disorder. Regurgitation of food even hours after a meal, unprovoked aspiration, and noisy deglutition (borborygmi) specifically suggest ZD. Other symptoms include belching, hypopharyngeal mucous collection, halitosis, choking, coughing, hoarseness, globus pharyngeus, weight loss, and recurrent respiratory infections. Symptoms may last for weeks to many years before diagnosis and are generally more severe with a larger ZD. Minimal physical findings may include mucous pooling in the hypopharynx that initially clears with swallowing then recurs, emaciation or dehydration, and, only rarely, a Boyce sign—a swelling in the neck that gurgles on palpation. However, it is more often the case that patients are without any specific findings on physical examination.

Diagnosis is confirmed by barium swallow radiography, which can also define the size and position of the sac ( Fig. 70.3 ). Fiberoptic endoscopy is also performed to help rule out other potential causes of dysphagia ( Box 70.1 ). Occasionally, ZD may be first discovered during esophagogastroduodenoscopy or rigid cervical esophagoscopy as an incidental finding during the course of a gastrointestinal evaluation. The size of the sac may range from less than 1 cm to a truly enormous 14 cm or more.

Through the years, physicians have attempted to classify ZD on the basis of contrast radiology findings ( Table 70.1 ). In 1930, Lahey described three stages based on radiologic appearance. Morton and Bartley, along with subsequent writers, also described three stages but based them on size. Rather than absolute size measurements, van Overbeek and Groote used cervical vertebral bodies as a standard for comparison. Brombart and Monges expanded the classification into four stages and incorporated size, appearance, and stage of deglutition. Others have created increasingly more complex categories that incorporate elements from both Brombart and Monges's and van Overbeek and Groote's systems. Although useful in terms of classifying ZD, these arrangements have limited clinical utility.

Pathophysiology

Although it is widely accepted that ZD is an acquired pulsion diverticulum, considerable controversy exists about the mechanism of its formation. Ludlow in Bristol, England, gave the first anatomic description of a pulsion diverticulum of the hypopharynx in 1769. He believed that the condition was induced in his subject by trauma after the swallowing of a cherry stone. Subsequent pathologists hypothesized traumatic rupture or burn, congenital upper esophageal stricture, thyroid goiter, or foreign bodies as triggers for ZD formation. It was not until 1877 that these hypotheses were rejected as erroneous, and the basic pathophysiology was described by, and the diverticulum named after, Zenker, a German pathologist. The original German description was later translated into English in New York in 1878 to allow wider dissemination of Zenker's findings. However, before Zenker, it was Bell (who is best known for describing facial nerve palsy) who proposed in 1816 that incoordination of the inferior constrictor muscle against a closed cricopharyngeal muscle resulted in this type of outpouching at regions of inherent weakness. This etiology was later supported by other researchers. Similarly, the congenital theory describes an unusually weak or large Killian triangle from birth that with time herniates with normal pharyngeal contraction. Variations on this theme for the mechanism of formation of ZD have been debated ever since.

Patterson first proposed cricopharyngeal achalasia as an etiology for ZD in 1919. Others noted a higher incidence of reflux and hiatal hernia in patients with ZD, as well as epidemiologic observations that ZD occurs predominantly in populations with a high incidence of reflux, which suggests a possible relationship between the two. Several writers in the early 1970s suggested that spasm or persistently elevated resting tone of the cricopharyngeus secondary to reflux could cause ZD, although others refuted a direct causal association. On the basis of histologic studies, Lerut in 1988 proposed a structural abnormality of the cricopharyngeal muscle itself. Cook et al. in 1992 suggested partial, incomplete opening of the cricopharyngeal muscle because of fibroadipose tissue replacement as an etiology. Six years later, Walters et al. proposed that ZD might be a manifestation of central or peripheral neurologic disease. Regardless of the theory, the cricopharyngeal muscle is the common theoretic culprit behind the formation of ZD, and whether to address this muscle during surgical management has been debated through the years.