<s>[INST] context: In 2-4% of people, a small poion of the vitelline duct persists, forming an outpocketing of the ileum, Meckel's/ ileal diveiculum Sometimes both ends of the vitelline duct transforms into fibrous cords, and the middle poion forms a large cyst, an enterocystoma/ vitelline cystVitelline duct, ay remain patent over its entire length, forming a direct communication between the umbilicus and the intestinal tract known as umbilical fistula/ vitelline fistulaVitello-intestinal duct or omphalo-mesenteric duct connects the midgut to the yolk sac during early embryonic life and gets obliterated and disappears during fifth to sixth week of intrauterine life. If the remnants persists then following abnormalities can occur:Umbilical Polyp: Umbilical polyp occur because of persistance of small poion of vitello-intestinal duct epithelium at the base of umbilicus.Umbilical Sinus: When umbilical poion of vitello-intestinal duct remains patent, an umbilical sinus forms.Fibrous remnant of vitello-intestinal duct: Whole vitello-intestinal duct become fibrous strand but does not disappear.Meckel's/ Ileal Diveiculum: The ileal poion of vitello-intestinal duct remains patent and form a diveiculum, called as Meckel's diveiculum.Patent Vitello-intestinal duct: When whole vitello-intestinal duct remains patent cause fistulous connection between umbilicus and ileum (umbilical fecal fistula)Mesenteric cystMesenteric cyst are thought to represent benign proliferations of ectopic lymphatics that lack communication with the normal lymphatic system.Mesenteric cysts can occur anywhere in the mesentery of the gastrointestinal tract from the duodenum to the rectum, and they may extend from the base of the mesentery into the retroperitoneum [/INST] question: Which is not associated with vitello-intestinal duct: | options: A: Ileal diveiculum B: Umbilical fistula C: Enterocystoma D: Mesenteric cyst | answer: D </s>