Melena: The black, tarry, foul-smelling FECES that contain degraded blood.Gastrointestinal Hemorrhage: Bleeding in any segment of the GASTROINTESTINAL TRACT from ESOPHAGUS to RECTUM.Hematemesis: Vomiting of blood that is either fresh bright red, or older "coffee-ground" in character. It generally indicates bleeding of the UPPER GASTROINTESTINAL TRACT.Diverticulum, Colon: A pouch or sac opening from the COLON.Ileal Neoplasms: Tumors or cancer in the ILEUM region of the small intestine (INTESTINE, SMALL).Duodenal Diseases: Pathological conditions in the DUODENUM region of the small intestine (INTESTINE, SMALL).Jejunal Neoplasms: Tumors or cancer in the JEJUNUM region of the small intestine (INTESTINE, SMALL).Jejunal Diseases: Pathological development in the JEJUNUM region of the SMALL INTESTINE.Endoscopy, Digestive System: Endoscopic examination, therapy or surgery of the digestive tract.Endoscopy, Gastrointestinal: Endoscopic examination, therapy or surgery of the gastrointestinal tract.Duodenal Neoplasms: Tumors or cancer of the DUODENUM.Arteriovenous Malformations: Abnormal formation of blood vessels that shunt arterial blood directly into veins without passing through the CAPILLARIES. They usually are crooked, dilated, and with thick vessel walls. A common type is the congenital arteriovenous fistula. The lack of blood flow and oxygen in the capillaries can lead to tissue damage in the affected areas.Ulcer: A lesion on the surface of the skin or a mucous surface, produced by the sloughing of inflammatory necrotic tissue.Capsule Endoscopy: Non-invasive, endoscopic imaging by use of VIDEO CAPSULE ENDOSCOPES to perform examination of the gastrointestinal tract, especially the small bowel.