These submucosal vessels are abnormally dilated and have thick walls.
The vessels are typically submucosal in location but may also involve the mucosa itself. Pathologic diagnosis may therefore be missed on the routine superficial mucosal biopsy.
Sometimes an abnormally thick vessels is detected within the muscularis propria.
Over time, the abnormal submucosal vessels begin to involve the mucosa itself.
A profound proliferation of capillaries in the mucosa can be seen here, but often times in small biopsies may not appear as prominent.
The mucosa then may undergo erosion, exposing the capillaries to the surface and a bleeding episode ensues.
Angiodysplasia of the colon is thought to be a degenerative phenomenon, secondary to either intermittent obstruction of the submucosal veins or hypoxemia.
Presents in older patients, typically as chronic recurrent bleeding which may appear clinically obscure. Rarely patients may suffer from massive hemorrhage. Lesions preferentially affect the right colon but may arise anywhere in the colon or small intestines. There are rare cases of angiodysplasia arising in children, even those under 1 year of age.
Selective embolization is the usual approach, although occasionally patients may require resection for uncontrolled bleeding. In those who have angiodysplasia secondary to Osler-Rendu-Weber disease or chronic renal failure, hormonal therapy with estrogen-progesterone may be employed.