Zenker Diverticulum 

Zenker diverticulum (ZD) was first described in 1769 by Ludlow. Zenker and von Ziemssen further characterized this entity in 1877. Although this condition was described in the literature numerous times between 1769 and 1877, Zenker's description was the most thorough, and his name has since been attached to it.

In 1866, Wheeler was the first to successfully perform surgical intervention. In 1917, Mosher described the first endoscopic approach.

Zenker diverticula are pulsion diverticula of the hypopharynx that occur primarily in older individuals, resulting in a life-altering and potentially life-threatening process. Zenker diverticula may be addressed by successful reliable surgical techniques.

Frequency

Zenker diverticulum occurs more commonly in certain parts of the world. It is observed most often in northern European countries and in countries whose population has a northern European heritage (eg, United States, Canada, Australia). Zenker diverticulum is rarely observed in Japan and Indonesia. Prevalence in high-risk countries is 2 cases per 100,000 people. Zenker diverticulum has a male-to-female ratio of 1.5:1 and is observed almost exclusively in older individuals.

Zenker diverticula occur in a muscular dehiscence that is present most commonly between the oblique muscle fibers of the inferior constrictor muscle and the transverse fibers of the cricopharyngeus (CP) muscle. This area is known as the Killian triangle. Other areas of muscular dehiscence occur between the oblique and transverse fibers of the CP muscle (ie, Killian-Jamieson area) and between the CP muscle and the esophageal muscles (ie, Laimer triangle). More inferiorly positioned Zenker diverticula may occur in one of these latter sites, as depicted in the image below.

Zenker diverticula may be staged in 1 of the following 3 systems, as assessed by means of barium swallow videofluoroscopy:

• Lahey system

  • Stage I: A small mucosal protrusion is present.
  • Stage II: A definite sac is present, but the hypopharynx and esophagus are in line.
  • Stage III: The hypopharynx is in line with diverticulum, and the esophagus is indented and pushed anteriorly.
• Morton system

  • Small sacs are less than 2 cm in length.
  • Intermediate sacs are 2-4 cm in length.
  • Large sacs are greater than 4 cm in length.
• van Overbeek system

  • Small sacs are less than 1 vertebral body in length.
  • Intermediate sacs are 1-3 vertebral bodies in length.
  • Large sacs are greater than 3 vertebral bodies in length.

Zenker diverticula extend into the left neck 90% of the time. This is likely due to the slight convexity of the cervical esophagus to the left side and to the more laterally positioned carotid artery on the left side, creating a potential space for the sac.

Although Zenker proposed a pulsion mechanism affecting the pharyngeal mucosa above the CP muscle, no consensus exists regarding a unifying concept of the pathophysiologic cause of Zenker diverticulum. The specific abnormality of the CP muscle has not been elucidated. Hypothetical abnormalities include the following:

• Abnormal timing of deglutition resulting in closure of the CP muscle when ideally it should be opening
• Incomplete CP muscle relaxation
• Elevated resting tone of the entire upper esophageal sphincter (UES)
• Loss of CP muscle elasticity
• CP muscle myopathy or denervation atrophy
• CNS injury with a focal spastic CP muscle
• CP muscle spasm in response to gastroesophageal reflux disease (GERD)

Studies to investigate the mechanism are scant. Cook histologically examined the CP muscle obtained at the time of diverticulectomy and found abundant fibrosis within the muscle. Whether this finding is a cause or a result of Zenker diverticulum is uncertain. Kern determined that older individuals exhibit less anterior excursion of the larynx and hyoid with deglutition than younger subjects, resulting in higher hypopharyngeal intrabolus pressures in older subjects.^[1] Whether this leads to Zenker diverticulum over time is speculative. van Overbeek suggested an anthropometric explanation. He felt individuals with longer necks had a larger Killian triangle, which predisposed them to formation of Zenker diverticulum.^[2]

The combination of the following symptoms is nearly pathognomonic for Zenker diverticulum:

• Dysphagia
• Regurgitation of undigested food hours after eating
• Sensation of food sticking in the throat
• Special maneuvers to dislodge food
• Coughing after eating
• Aspiration of organic material
• Unexplained weight loss
• Fetor ex ore
• Borborygmi in the neck

Symptoms may last from months to years.

The most common life-threatening complication is aspiration. Other complications include massive bleeding from the mucosa or from fistulization into a major vessel, esophageal obstruction, and fistulization into the trachea. Squamous cell carcinoma (SCC) within Zenker diverticulum is extremely rare, occurring in 0.3% of Zenker diverticula worldwide. A Mayo Clinic review suggests an incidence of 0.48% in the United States. Approximately 50 cases of invasive SCC and carcinoma in situ are reported in the literature. This possibility should be considered when evaluating patients with cervical metastatic SCC with an unknown primary cancer.

Zenker diverticula require intervention only if they produce symptoms. In general, small (ie, < 2 cm) lesions found incidentally require no intervention. However, some surgeons contend that since these lesions are likely to become larger with time, intervention ought to be considered in younger, healthier asymptomatic patients with Zenker diverticula.

Small lesions are satisfactorily treated with a CP myotomy with or without an invagination procedure. Intermediate and large diverticula (ie, 2-6 cm) are best managed by open diverticulectomy with CP myotomy or by endoscopic diverticulotomy. Very large diverticula (ie, >6 cm) are best managed with excision with CP myotomy or a diverticulopexy with CP myotomy, depending on the health of the patient. On one occasion, the authors placed a gastrostomy as the sole form of intervention for an ill 95-year-old patient with a 20-cm Zenker diverticulum.

See Etiology.

The overall health of people in this generally older population of patients may not allow a significant surgical undertaking. Recognition of this problem is essential in designing the ideal treatment plan. However, the range of effective treatment options allows treatment for essentially all symptomatic patients.

From an anatomic perspective, the most common open procedure (diverticulectomy with CP myotomy) has no contraindications. The endoscopic approach (diverticulotomy) may not be performed if the patient has significantly reduced cervical extension or marked trismus.