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Zenker’s diverticulum is an acquired mucosal herniation through an area of congenital muscle weakness in the cricopharyngeal muscle, known as Killian’s dehiscence. This opening is found in about one‐third of people at autopsy and has been described as occurring between the thyropharyngeus and cricopharyngeus or between the oblique and horizontal fibers of the cricopharyngeus itself [25, 26]. The pathogenesis of Zenker’s diverticulum is unknown. Manometric studies have produced conflicting findings [27, 28]. Some of these studies have shown a normal tonic pressure in the upper esophageal sphincter (UES) and normal coordination between pharyngeal contraction and relaxation of the UES, whereas others have shown elevated UES pressure or abnormal relaxation of the UES. It is also unknown whether chronic gastroesophageal reflux predisposes patients with Killian’s dehiscence to the development of a Zenker’s diverticulum. Nevertheless, most patients with Zenker’s diverticulum have a hiatal hernia and gastroesophageal reflex [29, 30].

Figure 6.8 Asymmetric epiglottic tilt. There is diminished epiglottic tilt on the left side (arrow).

When detected on barium studies, Zenker’s diverticulum appears on frontal views as a persistent, barium‐filled sac in the midline below the tips of the piriform sinuses (Figure 6.10). On lateral views during swallowing, the opening of the Zenker’s diverticulum above the incompletely opened pharyngoesophageal segment is often surprisingly broad [10, 31]. The sac then courses behind the pharyngoesophageal segment and proximal cervical esophagus. Barium within the diverticulum can be regurgitated back into the lower hypopharynx during breathing or additional swallowing (Figure 6.11), but overflow aspiration is uncommon. Contour deformities in a Zenker’s diverticulum may be caused by adherent debris, inflammation, or, rarely, carcinoma [32, 33].

Figure 6.9 Overflow aspiration. This man had global pharyngeal weakness due to polymyositis and poor clearance of barium from the pharynx during swallowing with resultant stasis of barium in the piriform sinuses. Note that the barium level lies above the interarytenoid notch (straight arrow). After the swallow has passed, barium pours over and down into the larynx (curved arrow), outlining the false vocal cords (right cord – f) and laryngeal ventricle.

Figure 6.10 Zenker’s diverticulum. (A) Frontal view of the pharynx demonstrates a 3 × 2 cm sac (S) with an air–barium level. The sac lies in the midline below the tips of the piriform sinuses (right piriform sinus tip identified by arrow). (B) Lateral view of the pharynx during drinking. The sac has a broad opening (double arrow). The sac (S) lies posterior to the pharyngoesophageal segment and proximal cervical esophagus (small arrows). (Laryngeal penetration resulted from abnormal timing between the oral and pharyngeal phases.

Source: Reproduced from Rubesin [10], with permission.

Figure 6.11 Pharyngeal regurgitation from Zenker’s diverticulum. (A) Frontal view of the pharynx shows a 2 cm sac (S) in the midline below the tips of the piriform sinuses. (B) Frontal view of the pharynx as the patient begins a second swallow. Barium (arrows) has been regurgitated from the Zenker’s diverticulum back into the lower hypopharynx.

Figure 6.12 Pseudo‐Zenker’s diverticulum. (A) Lateral view of the pharynx during drinking shows an open pharyngoesophageal segment (arrow) identified by redundant postcricoid mucosa. (B) Lateral view of the pharynx just after the bolus passes shows how the pharynx is descending to its “resting” position. Barium is trapped (thin arrow) between the early closing pharyngoesophageal segment (thick arrow) and the posterior pharyngeal contraction wave that has just passed. The transiently trapped barium entered the esophagus moments later. Note the difference in height of the pharyngoesophageal segment and the bottom of the vocal cords (open arrows) during and after swallowing.

Barium trapped above a prematurely or incompletely opened cricopharyngeus may resemble a small Zenker’s diverticulum and has been termed a pseudo‐Zenker’s diverticulum [24] (Figure 6.12). In such patients, no diverticulum is seen during swallowing. The sac‐like structure appears only when the cricopharyngeus closes early or when barium is trapped between the pharyngeal contraction wave and the incompletely opened cricopharyngeus. After a few moments, this barium enters the cervical esophagus, and the sac disappears. It is not known whether a pseudo‐Zenker’s diverticulum can progress to a true Zenker’s diverticulum. Early closure and incomplete opening of the cricopharyngeus have also been associated with GERD [34] (Figures 6.13 and 6.14).