During construction of an ileocecal reservoir, such as the Mainz or Indiana pouch, the ileocecal valve is lost. Subsequently, the intestinal transit time is shortened and malabsorption as well as diarrhea may result. Patients having undergone previous bowel resection as well as children with myelomeningocele who often already have frequent defecations will be heavily affected by the loss of the ileocecal valve. We have functionally reconstructed the ileocecal valve by embedding ileum into the ascending colon via a submucosal tunnel in analogy to the technique used when creating the continence mechanism during the Mainz pouch procedure using the appendix. Experimental results in 15 dogs demonstrated that the surgically reconstructed valve genuinely mimics the physiological function of the authentic valve and confirmed a marked transit time prolongation without evidence of obstruction. Our first clinical experience in 12 patients using this operative technique is promising. Equally, the morphological appearance of the newly created valve closely resembles the genuine ileocecal valve during barium enema as well as endoscopic investigations.