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Necrotizing enterocolitis (NEC) is the most common life-threatening
disorder of the gastrointestinal tract among neonates, primarily occurring
in infants born prematurely. It is characterized by inflammation
and patchy necrosis of the bowel wall that may rapidly progress
to systemic sepsis, bowel perforation, and death. Despite decades
of research, the underlying etiology remains poorly understood, preventive
strategies are inconsistent, and treatment options are controversial.
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The incidence of NEC is reported between 0.72 and 1.1 cases per
1000 live births.1,2 Its occurrence is inversely
related to birth weight and gestational age, the most important
and consistent risk factors in its development. Preterm infants comprise
the overwhelming majority of cases, with near-term and term infants
accounting for between 5% and 25%.3,4 For
very-low-birth-weight (VLBW) infants born at less than 1500 grams,
the incidence reported from large multicenter studies ranges from
approximately 5% to 12% of VLBW live births.1,5,6 Reports
from individual institutions, however, range widely, from as low
as 0.8% to 22%.6-8 Timing of
disease onset is inversely related to gestational age, with near-term
and term infants typically developing disease in the first week
of life, while onset is more common after the first or second week for
earlier gestational ages as shown in eFigure 57.1.9
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Mortality from NEC is related to gestational age, extent of bowel
involvement, and surgical intervention. In 2000, the in-hospital
US mortality across all weight categories was estimated to be 15.2% of
all NEC cases.1 Among very-low-birth-weight infants,
mortality from NEC varies from 12% to 30%,1,2 with
rates as high as 50% for extremely low-birth-weight infants
born at less than or equal to 1000 grams.10,11 Mortality increases
with the need for surgical intervention to as high as 50% and
is directly related to length of remaining intact bowel. Recent
data from Blakely and colleagues11 reported 75% survival
for infants with more than 80 cm of normal bowel at the time of
surgical intervention, 46% for infants with 10 to 80 cm
of normal bowel, and no survival in infants with less than 10 cm
of normal bowel present.11 Most large multicenter
studies have shown no significant change in NEC incidence over the
past 3 decades.2,5,12...