Intestinal atresia is a general phrase that refers to a full blockage or obstruction of the gut. Stenosis is a partial blockage that causes a narrowing of the intestine's aperture (lumen). The two conditions often occur together- many cases of intestinal atresia also have some degree of intestinal stenosis. The cause of both atresias and stenoses is usually unknown. They can be found in animals of all ages, but they are most common in newborns. These disorders affect the intestines only; other parts of the gastrointestinal tract are rarely involved. People with intestinal atresias are not able to digest certain foods because they have no working stomachs. This can lead to malnutrition if the condition is not treated promptly. If left untreated, intestinal atresias may require surgery to correct the problem or patients will need to rely on gastric juices for digestion. In people with intestinal stenoses, part of the intestine is unable to expand like the rest of the organ. This causes pain in response to eating food that cannot fit through the narrowed area. As a result, these individuals must ingest large amounts of food daily in order to feel full.