Ileal duplication cyst causing massive bleeding in a child. Intestinal duplication is a rare congenital anomaly; nonetheless, it comprises more than half of all alimentary duplication disorders. Our case report describes the hemorrhagic sequelae of this entity with surgical and pathologic findings. A review of anatomical classification, embryology, and natural history of duplication cyst follows; differentiating characteristics of duplication cyst versus Meckel's diverticulum are outlined. Intestinal duplication cyst should be considered in the differential diagnosis of GI bleeding, especially in children. 