Angiodysplasia

In medicine (gastroenterology), angiodysplasia is a small vascular malformation of the gut. It is a common cause of otherwise unexplained gastrointestinal bleeding and anemia. Lesions are often multiple, and frequently involve the cecum or ascending colon, although they can occur at other places. Treatment may be with colonoscopic interventions, angiography and embolization, medication, or occasionally surgery. Although some cases present with black, tarry stool (melena), the blood loss can be subtle, with the anemia symptoms predominating. Histologically, it resembles telangiectasia and development is related to age and strain on the bowel wall. It is a degenerative lesion, acquired, probably resulting from chronic and intermittent contraction of the colon that is obstructing the venous drainage of the mucosa. As time goes by the veins become more and more tortuous, while the capillaries of the mucosa gradually dilate and precapillary sphincter becomes incompetent. Thus is formed an arteriovenous malformation characterized by a small tuft of dilated vessels. Although angiodysplasia is probably quite common, the risk of bleeding is increased in disorders of coagulation. A classic association is Heyde's syndrome (coincidence of aortic valve stenosis and bleeding from angiodysplasia). In this disorder, von Willebrand factor (vWF) is proteolysed due to high shear stress in the highly turbulent blood flow around the aortic valve. vWF is most active in vascular beds with high shear stress, including angiodysplasias, and deficiency of vWF increases the bleeding risk from such lesions. Warkentin et al. argue that apart from aortic valve stenosis, some other conditions that feature high shear stress might also increase the risk of bleeding from angiodysplasia. Fecal occult blood testing is positive when bleeding is active. If bleeding is intermittent the test may be negative at times. Diagnosis of angiodysplasia is often accomplished with endoscopy, either colonoscopy or esophagogastroduodenoscopy (EGD).