Necrotising Enterocolitis
Necrotising enterocolitis (NEC) is acquired ischaemic and inflammatory necrosis of the immature neonatal bowel, in which bacterial gas tracks into the bowel wall and portal veins and necrosis perforates.
Definition
Necrotising enterocolitis is acquired inflammation and ischaemic necrosis of the neonatal bowel, ranging from suspected disease through definite intramural gas to transmural necrosis and perforation. The National Neonatal Audit Programme (NNAP) surveillance definition requires at least one clinical feature together with at least one radiographic feature. The clinical features are a bilious gastric aspirate or vomit, abdominal distension, and occult or gross blood in the stool. The radiographic features are pneumatosis intestinalis, hepatobiliary gas and pneumoperitoneum. Confirmation at surgery or post mortem also counts, and spontaneous intestinal perforation is excluded. Modified Bell staging then grades severity.
First principles
Prematurity sets the risk, and the numbers are gestation and birth weight
About 5 to 6% of babies born before 32 weeks develop NEC, and the East Midlands neonatal network guideline estimates nearly 12% of babies born below 1500 g. Risk climbs as gestation and birth weight fall, so the extremely preterm baby below 28 weeks or 1000 g carries the most. Term babies can get NEC when splanchnic perfusion is poor: duct-dependent congenital heart disease, perinatal asphyxia, polycythaemia, and growth restriction with absent or reversed end-diastolic flow (AREDF) on umbilical Doppler.
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