Zenker's Diverticulum

Anatomy & Pathophysiology:

Pharyngoesophageal diverticula, also known as Zenker diverticula (ZD), are acquired pulsion diverticula that result from herniation of the esophageal wall through areas of weakness in the pharyngeal musculature. Herniation in ZD most commonly occurs between the cricopharyngeus (CP) muscle and the inferior constrictor muscle at an area called Killian's triangle, although other areas of herniation are also possible, such as between the transverse and oblique fibers of the CP muscle (Killian-Jamieson's area). Zenker diverticula are most commonly located in the midline (>60%); however, larger diverticula may deviate laterally. ZD may range in size from 1 cm to over 10 cm in diameter and cause symptoms due to the accumulation of food in the diverticular pouch.

There are multiple theories as to the etiology of diverticular formation. One possibility is that patients with ZD have a lack of coordination between pharyngeal muscles during swallowing, with mistimed or incomplete relaxation of the CP muscle. Contraction of the inferior constrictor muscle against a contracted CP muscle results in increased pharyngeal pressure and promotes herniation. There is thought to be an association between ZD development and gastroesophageal reflux disease (GERD), perhaps because GERD promotes pharyngeal muscle spasm. Up to 50% of patients with ZD also have GERD.

Epidemiology:

Zenker diverticulum has an estimated incidence of 1 case per 50,000 people per year. Men are affected up to 3 times more than women, with peak incidence during the seventh and eighth decades of life. Geographically, ZD is most common in northern European countries, the United States, Canada, and Australia. ZD is seldom seen in Asian and African populations, in which GERD is also rare.

Natural History:

In general, untreated ZDs progressively herniate, with an associated increase in symptoms. This progression can be slow, however, with patients acquiring compensatory strategies for their symptoms.

Presentation:

Patients with ZD typically present with dysphagia and regurgitation of food, which may be delayed up to several hours after eating. Weight loss and recurrent pneumonia due to aspiration may also occur.

Differential Diagnosis of Dysphagia:

Evaluation:

History

Associated symptoms that may suggest neoplasm or systemic neurologic disease should be elucidated.

Physical Examination

Physical examination may be normal in many cases. Rarely, patients may present with a palpable, gurgling cervical mass, known as cervical borborygmi or Boyce's sign. Flexible fiberoptic laryngoscopic (FFL) examination may reveal hypopharyngeal pooling or food debris. Patients with GERD may have characteristic laryngoscopic findings associated with the condition as well Although FFL should be performed to rule out other causes of dysphagia (particularly pharyngeal or laryngeal neoplasm), it does not provide a definitive diagnosis for ZD.

Imaging Studies

Barium swallow radiography is the gold standard for ZD diagnosis and allows for quantification of diverticular size. Various classification schemes exist for ZD based on radiographic findings. Staging may be according to diverticular size, shape, orientation, or correspondence to phases of the deglutition process. However, clinical relevance of ZD classification as pertains to treatment approach and outcome has not been well established.

Treatment:

Definitive treatment of ZD is surgical, although some advocate observation for small (<2 cm), asymptomatic or minimally symptomatic diverticula. Absolute indications for treatment include persistent aspiration with recurrent respiratory infections and malnutrition or dehydration due to dysphagia and regurgitation. In individuals who are not surgical candidates, botulinum toxin injection of the CP muscle may provide symptomatic relief of dysphagia.

Surgical approaches to ZD involve resecting or opening the diverticular sac, with or without adjunctive cricopharyngeal myotomy. Traditionally, an external, transcervical approach was employed. This allows for complete excision of the diverticular sac, with concomitant CP myotomy. The external approach is, however, associated with risk of recurrent laryngeal nerve injury and fistula formation. With the development of endoscopic instrumentation, endoscopic diverticulotomy has become an attractive and viable alternative to complete excision of the sac. In this procedure, the common wall between the diverticulum and the esophagus is divided with an endoscopic stapler or laser. During this process, an internal CP myotomy is performed. Details regarding endoscopic Zenker diverticulotomy are presented in Endoscopic Zenker’s Diverticulotomy. In select cases of small diverticula, CP myotomy alone may be sufficient for symptomatic relief.

Complications, Prognosis & Follow-Up:

Symptoms may slowly progress with ZD. There is a small risk of carcinoma development within the diverticular sac, which increases with the duration of herniation. Potential surgical complications include recurrent laryngeal nerve injury, fistulization, infection, mediastinitis, pneumonia, aspiration, and dental trauma. In general, complication rates are low. Endoscopic approaches are associated with fewer complications; esophageal perforation is rare with the endoscopic approach. Endoscopic staple diverticulotomy has a reported success rate of over 90% in achieving symptomatic relief with recurrence rates between 0-20%. Possible causes of recurrence include incomplete CP myotomy and restenosis of the common wall due to scar formation. Because gastroesophageal reflux may promote scarring, patients should be placed on anti-reflux medication in the postoperative period. Revision endoscopic staple diverticulotomy is not associated with increased morbidity as compared to primary surgery; this is in contrast to revision external surgery, which carries a significantly higher complication and mortality rate.