Angiodysplasia · What Is It, Causes, Symptoms, and More

Angiodysplasia, also known as angioectasia or arteriovenous malformation, refers to tortuous (i.e., twisted) and swollen blood vessels in the mucosal and submucosal layers of the gastrointestinal (GI) tract. It is the most frequent etiology of small bowel bleeding in individuals older than 60 years of age.   

The segments of the GI tract are divided into four layers: the mucosa (epithelium, lamina propria, and muscularis mucosa), the submucosa, the muscularis propria (inner circular muscle layer, intermuscular space, and outer longitudinal muscle layer), and the serosa.  

In angiodysplasia, blood vessels directly adjacent to the lumen (i.e., opening) of the GI tract can become fragile and burst, leading to blood loss. It is the most common vascular malformation of the GI tract and most frequently occurs in the colon, but it can also affect the large intestine, small intestine, or stomach.  

While the exact mechanism causing angiodysplasia is unknown, it is thought that the contractility of the muscularis propria, the thick muscular layer of the GI tract, may increase, obstructing the submucosal veins. These veins drain the mucosal and submucosal layers as they pass through the muscularis propria. Over time, the obstruction may cause the submucosal veins, along with the venules and capillaries that drain them, to dilate and become tortuous.  

The prevalence of angiodysplasia increases with age and mainly occurs in individuals over 60. Risk factors include age-related degeneration of small blood vessels and cardiovascular and pulmonary diseases.  

Individuals with angiodysplasia may be asymptomatic or present with mild to moderate occult lower GI bleeding without abdominal pain. Occult bleeding refers to gastrointestinal bleeding that is not visible to the person or clinician but is detected through positive fecal blood tests.   

If angiodysplasia bleeds, the signs and symptoms can vary based on the source and location of the bleeding site. For example, slow bleeding from the stomach or small intestine may present as melena, which refers to dark and sticky feces; on the other hand, bleeding from the colon may present as passing bright, red blood (i.e., hematochezia).  

If there is excessive bleeding, or slow occult bleeding over a longer period of time, one can show symptoms of iron-deficiency anemia (e.g., excess fatigue, shortness of breath, heart murmur). In case of acute and heavy bleeding from the abnormal vessel, orthostasis and hypotension may occur.  

Angiodysplasia is typically diagnosed as an incidental finding during a colonoscopy performed for colorectal cancer screening, or within the evaluation of acute or chronic blood loss-related anemia.  

For its diagnosis, a medical history is typically obtained, assessing the presence of weakness, dizziness, or hematemesis. A physical exam is also usually conducted to assess vital signs and ensure the individual is hemodynamically stable. Various lab tests, including a complete blood count, liver function tests, coagulation studies, and renal function tests may be ordered to assess for anemia and diagnose underlying medical conditions associated with the rectal bleeding (e.g., end-stage renal disease, congenital or acquired coagulation disorders).   

To visualize angiodysplasia, upper endoscopy may also be performed. This non-surgical procedure involves inserting a flexible tube equipped with a light and camera through the mouth to examine the GI tract.  Since angiodysplasia can occur further along the GI tract, an upper endoscopy may not be able to visualize the lesion; in these cases, a capsule endoscopy may be used. During this procedure, a pill-sized capsule is swallowed and takes pictures as it travels through the digestive tract. Other diagnostic methods include radionuclide scanning images (i.e., an imaging technique that uses a small dose of a radioactive chemical), CT mesenteric angiography, and magnetic resonance angiography (i.e., procedures that use a dye and x-rays to see how blood flows through the arteries).  

When angiodysplasia is found incidentally, it does not require treatment if there is no history of GI bleeding or unexplained iron-deficiency anemia.  

If symptomatic, however, management often includes hemodynamic resuscitation, restoration of adequate tissue perfusion, complete blood count monitoring, and blood transfusions when necessary. To manage the source of bleeding, argon plasma coagulation (APC) ablation is the most commonly used intervention. APC is a medical endoscopic procedure  which uses argon gas and electrical current to cauterize bleeding vessels in the GI tract.  

Other interventions include electrocoagulation (i.e., heat from an electric current is used to destroy abnormal tissue), as well as endoscopic clips and band ligation, both of which are mechanical methods. Injection sclerotherapy, which involves injecting a sclerosant (i.e., a medicine causing vessels to shrink) to obliterate angiodysplasia, is another treatment option.  

Pharmacological therapies, such as somatostatin analogues and thalidomide, which inhibit new blood vessel formation among other effects, may be considered when angiodysplasia is refractory to endoscopic treatment.