Zenker's diverticulum overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:
Overview
In anatomy, Zenker's diverticulum, also pharyngoesophageal diverticulum, also pharyngeal pouch, is a diverticulum of the mucosa of the pharynx, just above the cricopharyngeal muscle (i.e. above the upper sphincter of the esophagus). It is a false diverticulum (not involving all layers of the esophageal wall).
Historical Perspective
he first description of Zenker's diverticulum dates back to 1769 by Ludlow.
Classification
Esophageal diverticula are classified on the basis of location into three types[1][2][3] Almost all esophageal diverticula are acquired pulsion diverticula. 1. Phrenoesophageal (Zenker's diverticulum-70%) ZD is a defect over the Killian's triangle, a point of weakness in the muscular wall of the hypopharynx 2. Epiphrenic (20%) Epipephric diverticula result either from hypertonia of the lower esophageal sphincter (esophageal achalasia) 3. Thoracic and mediastinal (10%) Thoracic diverticula are probably more often of a congenital than traction origin.
Pathophysiology
Zenker's diverticulum (ZD) is thought to be due to the result of motor abnormalities of the esophagus. The defect over the Killian's triangle, a point of weakness in the muscular wall of the hypopharynx results in ZD. Killian's triangle is surrounded by the cricopharyngeal sphincter and oblique fibers of the inferior constrictor of the pharyngeal muscle. It is considered a pseudodiverticulum as it includes only mucosa and submucosa. Chronic strain on the Killian's triangle leads to an evagination of the sphincter, which may be because of the high pressures in the food bolus in the course of swallowing and the abnormalities of the upper esophageal sphincter (UES). This failure to achieve adequate diameter for effective bolus clearance leads to a subsequent increase in the hypopharyngeal pressure gradient. Increased intra-bolus pressures found in patients with ZD can be secondary to impaired bolus passage combined with the gastroesophageal reflux disease (GERD) or as a result of the GERD. As the diverticulum enlarges, it may compress the pharyngoesophageal segment as well as increased stiffness and the intrabolus pressure. Increased intrabolus pressure is also increased in older patients who perform multiple swallows to achieve bolus clearance. Acid reflux is thought to lead to increased spasm of the UES which in turn increases the intra-bolus pressures during swallowing, given that swallowing is frequently distinct from episodes of acid reflux disease.
Causes
Zenker's diverticulum (ZD) also known as pharyngosophageal diverticulum. It is an acquired sac-like outpouching of the mucosa and submucosa layers originating from the pharyngoesophageal junction. Killian's dehiscence a pulsion of false diverticulum occurring dorsally at the pharyngoesophageal wall surrounded by the oblique inferior pharyngeal constrictor muscle and the transversal fibers of the cricopharyngeal muscle. ZD occurs due to increased intraluminal pressure in the oropharynx during swallowing, against an inadequate relaxation of the cricopharyngeal muscle. An incomplete opening of the Upper Esophageal Sphincter (UES) causing the protrusion of the mucosa through an area of relative weakness at the dorsal pharyngoesophageal wall. The pharyngoesophageal phase of swallowing is affected in ZD resulting in hindering the neuromuscular functions such as chewing, initiating the swallowing, and propulsion of the food from the oropharynx into the cervical esophagus.
Differentiating Zenker's diverticulum from Other Diseases
The differential diagnosis of the Zenker's diverticulum (ZD) are as follows Plummer-Vinson syndrome, reflux esophagitis, esophageal carcinoma, systemic sclerosis, achalasia, psuedoachalasia, chagas disease, esophageal candidiasis, pharyingitis and stoke.