Expansion
Duodenum for iron and calcium, jejunum for most nutrients, ileum for B12 and bile salts
Expansion
| Site | Absorbed |
|---|---|
| Stomach | Alcohol, some water and aspirin |
| Duodenum | Iron, calcium, magnesium, folate begins, fat-soluble vitamins |
| Jejunum | Most nutrients: sugars, amino acids, fats, water-soluble vitamins, folate |
| Ileum | Continued absorption of most nutrients |
| Terminal ileum | Vitamin B12 and bile salts |
| Colon | Water, electrolytes, short-chain fatty acids, vitamin K |
The clinically important sites are the two irreplaceable ones: the duodenum for iron and the terminal ileum for B12 and bile salts. Everything else has substantial functional reserve, which is why extensive jejunal resection is tolerated better than its length would suggest.
Consequences of resection:
- Duodenal or upper jejunal: iron deficiency anaemia
- Terminal ileal: B12 deficiency, bile salt diarrhoea, gallstones and oxalate renal stones
- Massive: short bowel syndrome, with the outcome depending on the length remaining, whether the ileocaecal valve is preserved, and whether the colon is in continuity