- Angiodysplasias are acquired ectasias of veins typically encountered in the elderly, that usually develop in the large intestine and have a propensity for bleeding.
- Angiodysplasias are characterized by dilated or tortuous small veins usually in the large intestine mucosa submucosa. In some cases, the pathologic veins may only be separated from the intestinal lumen by their endothelium and a thin layer of intestinal epithelium.
- Angiodysplasias typically result in intermittent lower GI bleeding that can be significant although rarely massive. This pathology is a significant source of occult lower GI bleeding in the elderly.
- Angiodysplasias are thought to have a mechanical etiology and may occur as a result of a lifetime of repeated colonic peristaltic contractions. This pattern of contraction increases the pressure within the large intestine muscularis mucosa resulting in collapsing of veins but not arteries and thus dilation of smaller, upstream superficial veins. The propensity for the large intestine may arise from the fact that this segment of the alimentary tract has the largest luminal diameter and so according to Law of Laplace, requires the most tension for contraction.