Intestinal obstruction
- Lesion
The bowel can be blocked by being trapped in a hernia, tied by scar bands, twisted on itself or telescoped into the next segment.
What it is
Obstruction can occur at any level but most often in the small intestine, whose lumen is narrow. Four mechanical causes account for about four in five cases: hernias, adhesions, volvulus and intussusception; tumours, infarcts and strictures (for example Crohn disease) make up the rest. The danger is not only the blocked lumen but the blood supply: trapped or twisted bowel loses venous drainage first, then arterial inflow, and infarcts.
Structure
- Strangulated loop: dusky, purple, haemorrhagic serosa with a sharp edge at the neck of the trap.
- The telescoped segment (intussusceptum) drags its mesentery into the receiving segment (intussuscipiens).
Step by step
- A segment of bowel is trapped, kinked, twisted or telescoped.
- Thin-walled veins are compressed first: congestion and oedema.
- Swelling traps the loop further (incarceration).
- Arterial inflow is cut: strangulation.
- Haemorrhagic infarction, then perforation and peritonitis.
The four mechanical causes
| Cause | Mechanism | Who | Clue |
|---|---|---|---|
| Hernia | Bowel in a peritoneal sac through a wall defect | Any age | Groin or umbilical swelling |
| Adhesions | Fibrous bands form loops that trap bowel | After surgery or peritonitis | Previous laparotomy |
| Volvulus | Twist around the mesenteric attachment | Older adults (sigmoid); infants with malrotation (midgut) | Coffee-bean loop on imaging |
| Intussusception | A segment telescopes into the next one | Infants; adults with a tumour lead point | Currant-jelly stool, sausage mass |
Clinical notes
- Air or contrast enemas can both diagnose and reduce idiopathic intussusception in young children.
- In cystic fibrosis, sticky stool can act as the lead point of intussusception.
Test yourself
Think of the answer, then tap the question to see it.
What are the four main mechanical causes of intestinal obstruction?
Hernias, adhesions, volvulus and intussusception.
Why does a strangulated hernia infarct?
Pressure at the neck first blocks venous drainage, the loop swells, and arterial supply is then cut off.
What usually serves as the lead point of intussusception in adults?
An intraluminal mass or tumour.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Small Bowel Obstruction (StatPearls (NCBI Bookshelf), 2025); Sigmoid Volvulus (StatPearls (NCBI Bookshelf), 2025); Child Intussusception (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.