Cricopharyngeus, aortic arch, left main bronchus and the diaphragmatic hiatus
Mnemonic
Four constrictions, at 15, 22, 27 and 40 cm from the incisors:
- 15 cm - cricopharyngeus, the upper oesophageal sphincter at C6. The narrowest
- 22 cm - aortic arch crossing
- 27 cm - left main bronchus crossing
- 40 cm - the diaphragmatic hiatus at T10
“Cricoid, arch, bronchus, hiatus”, and some texts merge the middle two into a single broncho-aortic constriction, giving three.
These are where foreign bodies lodge, where strictures form after caustic ingestion, and where carcinoma most often arises.
Cricopharyngeus is the narrowest point of the entire gastrointestinal tract, which is why it is the commonest site of impaction and why it is the site of perforation during oesophagoscopy and of a pharyngeal (Zenker’s) pouch through Killian’s dehiscence.
The distances matter practically for nasogastric tube and endoscope insertion depths.
Expansion
Working down from the mouth:
| Constriction | Distance from incisors |
|---|---|
| Cricopharyngeus (upper oesophageal sphincter) | 15 cm |
| Arch of the aorta | 22 cm |
| Left main bronchus | 27 cm |
| Diaphragmatic hiatus | 40 cm |
These are the sites where swallowed foreign bodies impact, where corrosive injury is most severe because contact time is longest, and where carcinoma most often causes early obstruction.
The two middle constrictions are both compressions from outside, produced by structures crossing the oesophagus, a useful way of remembering that only the first and last are sphincteric.