Necrotizing enterocolitis is a relatively common yet dangerous condition seen in the NICU. It occurs when there is an ischemic or toxic insult to the bowel mucosa; often this insult is perinatal hypoxia. When this occurs, there is a loss of mucosal integrity, and the mucosa is invaded by bacteria or viruses. This may progress to bowel wall necrosis or gangrene. Ultimately, the bowel wall may perforate. NEC most commonly begins in the distal ileum to proximal colon, but it can progress to encompass the entire bowel.
NEC usually onsets three to seven days after the initiation of enteral
feedings. It is thought that the feeding provides enteric organisms
with the substrates necessary for their multiplication. Although
about 10 percent of infants under 1500 grams will develop NEC, about 10
to 25% of NEC cases occur in low risk and full term infants. The
mortality rate from NEC with perforation of the bowel is about 20-40%.