Cystic fibrosis associated meconium ileum is a thickening and congestion of the meconium in the ileum in newborns, often the first sign of cystic fibrosis. In cystic fibrosis, the meconium can form a bituminous black-green mechanical obstruction in a segment of the ileum. Beyond this there may be a few separate grey-white globular pellets. Below this level, the bowel is a narrow and empty micro-colon. Above the level of the obstruction, there are several loops of hypertrophied bowel distended with fluid. No meconium is passed, and abdominal distension and vomiting appear soon after birth. About 20% of cases of cystic fibrosis present with meconium ileus, while approximately 20% of one series of cases of meconium ileus did not have cystic fibrosis. The presence of meconium ileus is not related to the severity of the cystic fibrosis. The disease is Monarch Disease Ontology identifier MONDO_0005413 (cystic fibrosis associated meconium ileus). Also known as: cystic fibrosis associated meconium ileum.