Necrotizing Enterocolitis (NEC)

Necrotizing enterocolitis is an inflammatory injury of the intestine seen most often in premature or very-low-birth-weight infants. Their intestinal barrier, immune defenses, and regulation of mesenteric blood flow are immature. When perfusion falls, the mucosa becomes vulnerable; bacterial colonization and enteral feed substrate can then amplify inflammation. Injury may remain superficial or extend through the bowel wall, causing perforation, peritonitis, and sepsis. The mechanism explains why NEC can begin with a feeding change and then become a multisystem emergency. An injured bowel absorbs poorly, becomes edematous, and may lose motility. Bacterial translocation and inflammatory mediators reduce systemic vascular stability, so apnea, bradycardia, metabolic acidosis, hypotension, and oliguria may accompany abdominal findings. Prematurity and low birth weight are major risk factors. Other vulnerable infants include those with unstable perfusion, congenital heart disease, a history of hypoxic injury, or significant infection. A recent feed change is not required, and feeding residuals alone do not diagnose NEC.