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CHAPTER 70

Necrotising Enterocolitis

Avraham Schlager
Marion Arnold
Samuel W. Moore
Evan P. Nadler

Introduction suspected disease known as an “NEC scare” at some point during their
Necrotising enterocolitis (NEC) is a disease of the infant gastroin- postnatal care. 7,14 Additionally, several reports have suggested that there
testinal tract (GIT) most commonly found in premature newborns. may be an inverse relationship between gestational age and the age at
Although the aetiology and pathogenesis of the disease is not fully onset of the disease. 15,16 Snyder et al. have recently reported that VLBW
understood, in its most severe cases, NEC rapidly progresses from infants developed NEC later than their higher-weight cohorts, which
bacterial invasion of the intestinal wall to full-thickness bowel necrosis, may suggest that birth weight and age at the onset of disease may also
16
leading to perforation and subsequent peritonitis, sepsis, and possibly be inversely related.
death. The elusive nature, unpredictable onset and progression, as well Although the disease does not exclusively affect premature infants,
1
as the fragile nature of the affected patient population, combine to make nearly 90% of patients who develop NEC are premature. When
NEC one of the leading causes of morbidity and mortality in neonatal NEC does occur in term infants, it is almost always associated with
intensive care units (NICUs) globally. 2,3 comorbidities that promote intestinal ischaemia (e.g., congenital heart
Although technological advances, such as the advent of the disease, neonatal asphyxia, maternal pre-eclampsia, and diabetes) or
modern intensive care unit (ICU), initially yielded fairly dramatic causes of intestinal obstruction such as Hirschsprung’s disease.
improvements in the survival of patients with NEC, the condition Reported NEC mortality in the United States ranges from 15% to
4,5
is still associated with a sustained high mortality (19–50%), even 30%, with smaller infants, infants with more extensive disease, and
7
in developed countries, with little improvement over the last two infants requiring surgery at the greatest risk. Although the mortality
6
decades. These advances have been accompanied by a dramatic rise rates in industrialised nations have been decreasing over the past 30
7
in the cost of treating patients with NEC. As a result, the challenges years due to early detection, implementation of preventive measures,
facing clinicians in First World nations are magnified in developing and upgrading of intensive care support facilities, this success has not
17
countries, where medical care is often constricted by dilemmas of triage been shared by developing countries due to limited resources.
and allotment of limited resources. Aetiology/Pathophysiology
Demographics Despite extensive research in the field, an adequate understanding of
Necrotising enterocolitis is the most common cause of death in surgical the aetiology and pathophysiology of NEC remains elusive. Current
8
neonates worldwide. Although the prevalence of NEC varies geo- knowledge of the cause and course of NEC has been confined to asso-
graphically and temporally, sometimes occurring in clusters or epidem- ciated risk factors and recognised patterns of pathophysiologic change.
ics, the overall incidence in the United States is estimated to be 1–3 Although any portion of the intestinal tract may be involved, NEC
9
cases for every 1,000 live births. Due to improvements in technology most commonly affects the terminal ileum. Its frequent distribution to
and perinatal care and the concomitant increase in survivability of neo- the distal ileum and right side of the colon suggests a local vascular
nates, the incidence of the disease appears to be increasing in Western component because this area is most removed from the blood supply.
10
nations. Interestingly, there appears to be an overall increase in NEC The histologic hallmark of NEC is a “bland infarct,” which is
prevalence in developing countries in recent years as well. This may be characterised by full thickness coagulation (ischaemic) necrosis, a
partly attributed to factors such as the increased survival of very small paucity of acute inflammatory cells (neutrophils), and a predominantly
18
premature infants, the increasing drug abuse culture, and the high inci- lymphocytic infiltrate (Figure 70.1). Santulli and colleagues described
dence of preterm labour (especially in developing countries), as well as a classic triad of pathological events leading to the development of
the impact of the HIV epidemic currently sweeping over sub-Saharan NEC, including (1) intestinal ischaemia, (2) colonisation by pathogenic
19
Africa, where an increase in severity can probably be anticipated. bacteria, and (3) excess protein substrate in the intestinal lumen.
Accurate statistical analysis of the disease in continental Africa is not Using this triad, Kosloske et al. hypothesised that quantitative extremes
feasible because the poor access to antenatal diagnosis, primary health of two out of three of these factors is sufficient to cause NEC. 20
care, transport facilities, and low survival of infants with delayed pre- Mucosal ischaemia arises from a neonatal insult resulting from
sentation significantly contribute to the decreased number of recorded factors such as a decrease in end diastolic blood flow, foetal distress,
11
admissions with the diagnosis of NEC. cold exposure, asphyxia, hypotension, congenital heart disease, or
sepsis. Intestinal ischaemia results in local production of free radicals
Epidemiology and Incidence and initiates a cytokine cascade within the gut wall.
NEC is the most frequent and most lethal disease affecting the GIT Novel treatments are currently being developed to abrogate the
of premature infants. The disease appears to display no particular toxic effects of some of the local factors at play in the inflammatory
12
ethnic predilection. Prematurity remains the most consistent risk fac- process. As a result of the mucosal damage, bacterial translocation can
21
tor for developing NEC, with incidence and mortality from NEC both occur through the intestinal wall, and systemic infection may follow,
13
inversely related to birth weight and gestational age. Approximately leading to further ischaemia and necrosis of the bowel wall, progression
7–10% of very low birth weight (VLBW) infants (<1,000 g) suffer to perforation, peritonitis, overwhelming septicaemia, and possible
from NEC, and almost 20% of these newborns experience a period of multiorgan failure and death.