What is achalasia?
Achalasia is failure of the muscle (sphincter) in the lower food pipe (oesophagus) to relax. Normally when we swallow waves of muscle contractions (peristalsis) push the food down the oesophagus into the stomach. For this to happen the lower oesophageal sphincter needs to relax. The lower oesophageal sphincter is normally closed at rest to stop food moving up into the oesophagus (reflux).
Failure of the muscle to relax results in an inability to swallow which causes a buildup of food in the oesophagus. A secondary effect is that the peristaltic contractions stop working and the oesophagus becomes enlarged and floppy (mega-oesophagus).