How to classify esophagus as upper middle and lower one third in endoscopy
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esophagus upper middle lower third classification endoscopy distance incisors cm
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https://basicmedicalkey.com/the-anatomy-of-the-esophagus
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Esophageal Classification into Upper, Middle, and Lower Thirds at Endoscopy
The esophagus is measured from the upper incisor teeth during endoscopy. The total endoscopic length of the adult esophagus runs from approximately 15-20 cm (upper esophageal sphincter/cricopharyngeus) to 38-40 cm (gastroesophageal junction/Z-line).
Key Landmarks First
| Landmark | Distance from Incisors |
|---|---|
| Upper esophageal sphincter (cricopharyngeus) | ~15-17 cm |
| Aortic arch / left main bronchus indentation | ~25 cm |
| Lower esophageal sphincter / Z-line (GEJ) | ~38-40 cm |
Two Classification Systems (Both in Use)
System 1 - Anatomical Segments (used in surgical/oncologic staging)
| Segment | Borders | Distance from Incisors |
|---|---|---|
| Cervical esophagus | Lower pharynx to thoracic inlet | 15-18 cm |
| Upper thoracic | Thoracic inlet to lower border of azygos vein | 18-23 cm |
| Middle thoracic | Azygos vein to inferior pulmonary veins | 24-32 cm |
| Lower thoracic + abdominal | Inferior pulmonary veins to GEJ | 32-40 cm |
System 2 - Simple Thirds Classification (used clinically for variceal grading, cancer staging, and endoscopic reporting)
| Segment | Distance from Incisors | Notes |
|---|---|---|
| Upper third | 20-25 cm | Corresponds to thoracic inlet region; 10% of esophageal cancers |
| Middle third | 25-32 cm | Level of carina and aortic arch; 40% of esophageal cancers |
| Lower third | 32-40 cm | Above the GEJ; 50% of esophageal cancers |
Some sources use 20 cm as the starting point (just below the cricopharyngeus), so the upper third begins at 20 cm and the total functional esophageal length is divided into three roughly equal segments of ~7 cm each.
Practical Endoscopic Reference
- 15-20 cm - Hypopharynx / cricopharyngeal muscle - entering the esophagus
- 20-25 cm - Upper third
- 25-32 cm - Middle third (at ~25 cm you see the pulsation of the aortic arch)
- 32-40 cm - Lower third
- 38-40 cm - Z-line (squamocolumnar junction, gastroesophageal junction)
Clinical Importance of This Classification
-
Esophageal varices - grading and treatment planning distinguishes lower third (most important for bleeding risk), middle third, and upper third varices. The lower third varix size is the most clinically significant predictor of hemorrhage (per Sleisenger and Fordtran's GI and Liver Disease).
-
Esophageal cancer - The TNM and ICD staging uses upper/middle/lower third location (ICD codes 150.3, 150.4, 150.5) because it influences surgical approach (cervical anastomosis vs. thoracic vs. abdominal).
-
Caustic ingestion - The three natural narrowings at ~15-17 cm, ~25 cm, and ~38-40 cm are the most vulnerable sites.
-
Barrett's esophagus - Landmarks are reported in cm from the incisors (e.g., "Z-line at 38 cm, hiatal hernia from 36-38 cm").
Memory Aid
A simple way to remember for a standard adult:
- The esophagus starts at ~20 cm and ends at ~40 cm from the incisors - a functional length of 20 cm.
- Divide 20 cm into thirds: each third is roughly ~7 cm.
- Upper: 20-27 cm | Middle: 27-33 cm | Lower: 33-40 cm (some variation exists between sources)
The World Endoscopy Organization's Minimal Standard Terminology (MST v3.0) standardizes reporting as: upper third, middle third, lower third, Z-line - with exact cm from incisors documented alongside each finding.
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