Zenker's diverticulum mainly affects older adults.
In simple words, when there is excessive pressure within the lower pharynx, the weakest portion of the pharyngeal wall balloons out, forming a diverticulum which may reach several centimetres in diameter.
More precisely, while traction and pulsion mechanisms have long been deemed the main factors promoting development of a Zenker's diverticulum, current consensus considers occlusive mechanisms to be most important: uncoordinated swallowing, impaired relaxation and spasm of the cricopharyngeus muscle lead to an increase in pressure within the distal pharynx, so that its wall herniates through the point of least resistance (variously known as Killian's triangle, Laimer's triangle, and the Killian-Laimer triangle). The result is an outpouching of the posterior pharyngeal wall, just above the oesophagus. As the outpouching involves solely the mucosa, it is considered a false diverticulum.
While it may be asymptomatic, Zenker diverticulum often causes clinical manifestations such as dysphagia (difficulty swallowing), and sense of a lump in the neck; moreover, it may fill up with food, causing regurgitation (reappearance of ingested food in the mouth), cough (as some food may be regurgitated into the airways), halitosis (smelly breath, as stagnant food is digested by microrganisms) and involuntary gurgleing noises when swallowing. It rarely causes any pain.
If small and asymptomatic, no treatment is necessary. Larger, symptomatic cases of Zenker's diverticulum have been traditionally treated by neck surgery to resect the diverticulum and incise the cricopharyngeus muscle. However, in recent times non-surgical endoscopic techniques have gained more importance (as they allow for much faster recovery), and the currently preferred treatment is endoscopic stapling (i.e. closing off the diverticulum via a stapler inserted through a tube in the mouth). This may be performed through a fibreoptic endoscope.
Other non-surgical treatment modalities exist, such as endoscopic laser, which recent evidence suggests it less effective than stapling.