A diverticulum is a sac or pouch arising from a tubular organ, such as the esophagus. This article focuses on diverticula of the esophagus. As is common practice, Zenker diverticulum, a type of diverticulum that arises from the posterior hypopharynx, is also discussed in this article.
Esophageal diverticula are classified by location in the esophagus. Upper (pharyngoesophageal, Killian-Jamieson, or Zenker), middle, or lower (epiphrenic). Besides anatomical location, several other ways to classify diverticula of the esophagus and hypopharynx exist. Congenital diverticula are diverticula that are present at birth, while acquired diverticula develop later in life. Diverticula of the esophageal body can sometimes be difficult to classify as congenital or acquired. 
Diverticula also may be classified on the basis of histopathology. True diverticula contain all layers of the intestinal tract wall. False diverticula, also known as pseudodiverticula, occur when herniation of mucosa and submucosa through a defect in the muscular wall occurs (eg, Zenker diverticulum). A special type of pseudodiverticula, believed to represent dilated excretory ducts of esophageal submucosal glands, is observed in the condition esophageal intramural pseudodiverticulosis.
Finally, acquired diverticula of the esophagus and hypopharynx also may be classified according to their pathogenesis as pulsion diverticula or traction diverticula. Pulsion diverticula form as a result of high intraluminal pressures against weaknesses in the GI tract wall. Zenker diverticulum occurs due to increased pressure in the oropharynx during swallowing against a closed upper esophageal sphincter. An epiphrenic diverticulum occurs from increased pressure during esophageal propulsive contractions against a closed lower esophageal sphincter.  In contrast, traction diverticula occur as a consequence of pulling forces on the outside of the esophagus from an adjacent inflammatory process (eg, involvement of inflamed mediastinal lymph nodes in tuberculosis or histoplasmosis).
Most esophageal diverticula occur in middle-aged adults and elderly people. Presentation in infants and children is rarely seen.
Zenker diverticula typically present in people older than 50 years and especially present during the seventh and eighth decades of life.
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