Angiodysplasia
- Lesion
Tangles of thin, widened blood vessels in the right colon can bleed slowly or heavily in older people.
What it is
Angiodysplasia is a malformation of submucosal and mucosal vessels, most often in the caecum and right colon, that usually shows after age sixty. Although present in under one percent of adults, it accounts for about a fifth of major lower intestinal bleeds in older people. The favoured explanation is mechanical: repeated contraction of the bowel wall partly blocks the veins that pierce the muscle, and the vessels upstream dilate; the caecum, with the widest diameter and highest wall tension, is most exposed.
Structure
- Endoscopy: small flat red, fern-like vascular lesions.
- Micro: clusters of dilated thin-walled vessels in mucosa and submucosa, close to the surface.
Step by step
- Bowel contraction intermittently compresses submucosal veins where they cross the muscularis propria.
- Venous outflow is partly obstructed, again and again over years.
- Upstream venules and capillaries dilate and become tortuous.
- Only a thin wall and epithelium separate them from the lumen; minor injury makes them bleed.
Clinical notes
- Consider it in an older person with recurrent painless bleeding and iron deficiency once tumours are excluded.
- Diverticular disease and angiodysplasia are the two classic causes of brisk lower GI bleeding in older adults.
Test yourself
Think of the answer, then tap the question to see it.
Where in the colon is angiodysplasia most common?
In the caecum and right colon.
What mechanism is thought to cause angiodysplasia?
Repeated partial blockage of submucosal veins by contraction of the bowel wall, with dilation of upstream vessels; wall tension is highest in the caecum.
What does angiodysplasia look like microscopically?
Ectatic, tortuous thin-walled veins, venules and capillaries in mucosa and submucosa, close to the surface.
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: Gastrointestinal Bleeding (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.