Pathophysiology and Clinical Presentation of Achalasia

Achalasia of the oesophagus is a disease which has achieved more importance than would be expected, considering its extreme rarity. This is due partially to the excitement of seeing a large dilated oesophagus on x-ray but mainly because it demonstrates what can go wrong with normal physiology. The healthy oesophagus consists of a hollow muscular tube closed by a sphincter at each end, and is normally kept completely empty by a primary peristaltic wave which sweeps the lumen clear after each swallow. The cricopharyngeal sphincter prevents air entering when one breathes and the lower oesophageal sphincter stops the reflux of gastric contents. A secondary peristaltic wave can occur in response to distension by refluxed gastric contents and this is an additional mechanism to keep the oesophagus empty. In achalasia there is retention of food and drink in the body of the oesophagus and the normal reflexes for completely clearing the lumen are absent. There are no peristaltic waves in the body of the oesophagus and the lower oesophageal sphincter fails to relax in response to each swallow. These abnormalities are due to the loss of ganglion cells in Auerbach's plexus. The denervated muscle can still contract, but it is inefficient and incoordinated.