Paediatrics, prematurity-related diseases: necrotising enterocolitis

By Cristiano Antonino On May 24, 2023

Necrotising enterocolitis is a serious intestinal disease related to prematurity. Symptoms appear in the second week of life

Treatment is medical or surgical depending on the severity

Necrotising Enterocolitis (NEC from Necrotizing EnteroColitis) is a severe intestinal disease of the newborn.

‘Entero’ means intestinal.

‘Colitis’ means inflammation of the colon.

‘Necrotizing’ means damage and cell death of the intestines.

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Necrotizing enterocolitis (NEC) is the highest mortality gastrointestinal disease in neonatal age

It affects about 1 in 1000 live births, and can affect up to 7% of very low birth weight infants.

It is the cause of death in approximately 15-30% of premature infants affected.

It is a disease related to prematurity.

Term infants who develop necrotising enterocolitis generally have risk factors such as congenital heart disease, septicaemia or hypotension (low blood pressure).

The underlying causes are not completely known and are probably multiple.

Necrotising enterocolitis is believed to be an inflammatory disease that is triggered when enteral nutrition is started in the second week of life, which is often used in low-birth-weight infants.

The intestinal mucosa of these infants is attacked by a severe reduction in blood supply, resulting in lesions of the inner surface of the intestine.

These lesions can become infected to the point of extensive necrosis that may require removal of the affected intestinal segments.

Usually the ischaemic attack occurs at the level of the ileum (the final part of the small intestine) but, in fact, any segment of the gastrointestinal tract can be affected.

Necrotising enterocolitis is classified according to the severity of clinical damage according to Bell’s staging (modified by Walsh and Kliegman)

Stage I (suspected necrotising enterocolitis);
Stage II (definite stage necrotising enterocolitis);
Stage III (advanced stage necrotising enterocolitis).

In the early stage, the symptoms of necrotising enterocolitis (NEC) are

Intolerance to mouth/enteral feeding;
Gastric stagnation;
Abdominal distension;
Biliary vomiting;
Macroscopic (evident to the naked eye) or occult blood in the faeces.

In the second stage, necrotising enterocolitis manifests itself with the following symptoms

Tight abdomen and pain on palpation;
Digestive symptoms;
Lethargy (deep sleep state);
Apnoea (momentary cessation of respiratory movements);
Cardiovascular problems that may require recourse to intensive care.

Each stage of the disease corresponds to a different treatment

Necrotising enterocolitis (NEC) in most cases can only be managed with medical therapy, but there is a 20-40% chance of having to resort to surgery (surgical indication is present in the advanced stage of the disease).

These are precisely the cases in which immediate mortality is highest (up to 50%), especially if the infant has a low birth weight.

Necrotising enterocolitis (NEC) also leads to intestinal surgery and is responsible for significant long-term morbidity related to the onset of short bowel syndrome (SBS).

Short bowel syndrome (SBS), which is an extensive pathological condition, has an increasing incidence (correlated with increased rates of prematurity) and long-term management involving nutritional and surgical technique and a multidisciplinary approach.

The examination highlights the symptoms listed above.

The necessary laboratory tests are

CBC test demonstrating increased white blood cells and low platelet count;
Acid-base balance demonstrating metabolic acidosis;
Blood glucose which may show high (hyperglycaemia) or low (hypoglycaemia);
Electrolytes.

Instrumental tests are also necessary

X-ray of the abdomen showing the presence of hydroaerial levels. Subsequently, intestinal pneumatosis (presence of gas inside the intestine) and the aerial portogram (presence of gas in the portal venous system) may occur. The development of pneumoperitoneum (presence of air in the peritoneum, i.e. in the abdomen outside the intestine) suggests evolution towards intestinal perforation.
Infants with necrotising enterocolitis (NEC) who do not require surgery (medical NEC) have similar long-term outcomes to premature infants who do not have necrotising enterocolitis (NEC).
In suspected necrotising enterocolitis (Bell’s stage I disease), infants are fasted (intestinal rest) and given intestinal decompression (low-intermittent orogastric suction) and broad-spectrum antibiotic therapy.
Additional therapy including cardiovascular support (blood pressure, volume), pulmonary support (oxygen, ventilation) and haematological support (blood transfusion) may be required as appropriate.
If the clinical course and radiological and laboratory test results remain consistent with suspected necrotising enterocolitis or Bell’s stage I disease, the duration of medical treatment will usually be dictated by clinical judgement.
In suspected necrotising enterocolitis (NEC) (stage I) and definite NEC (stage II) medical treatment should be continued for 7-14 days and closely monitored for possible evolution to stage III (advanced NEC).

The mainstay in the treatment of medical necrotising enterocolitis (NEC) (phase I and II) (and prevention of surgical NEC) is

a) Proper management of fluid intake;
b) Nutrition;
c) Infection prevention and appropriate antibiotic therapy;
d) Pain management;
e) Ongoing assessment, investigation and management.

In some cases, surgery is required.

Indications for surgery include clinical deterioration, perforation, peritonitis, obstruction and abdominal mass.

Referral to surgical services should be made immediately after the diagnosis of progressive disease.

When bowel resection is required (Bell Stage III or surgical NEC) it is important to remember how the surgical act strongly impacts on prognosis and future nutritional management so surgery should aim at 3 main objectives

To spare as much intestinal tissue as possible: the length of the resected intestinal tract and therefore of the residual bowel has significant long-term implications.

a) This is so important that today’s literature and surgical practice envisages at first look a resection limited only to the intestine with evident necrosis and then, in subsequent multiple laparotomies, proceeding to further resections only if not improved. The aim is precisely: to save as much tissue as possible.

b) Minimising damage to liver tissue: especially premature infants with a very low birth weight have an extremely fragile liver parenchyma and even relatively trivial retraction injuries can cause major haemorrhage with catastrophic consequences.

c) Provide stable venous access for medical management and parenteral nutrition (NP) administration.

The administration of breast milk or donated human milk is critical in both the prevention of necrotising enterocolitis (NEC) and the treatment of surgical necrotising enterocolitis (NEC) (stage III, advanced NEC).

Unfortunately, we have no nutritional strategies that are effective in preventing necrotising enterocolitis (NEC), but the evidence we have suggests that it is safe to start enteral nutrition within 96 hours of birth, increase it quickly and use bolus nutrition.

Given the great variability observed in feeding strategies, it is recommended that at least every neonatal intensive care unit should have a standardised protocol for initiating nutrition to ensure adequate supplies and minimise complications.

Further studies are needed on

Special populations of infants (infants weighing less than 1000 g and with a gestational age between 28 and 32 weeks);
Possible markers of disease severity and progression;
Effect of specific nutrients on the intestinal adaptation process.

With regard to this last point, there is evidence, although not conclusive, on the beneficial effect of a high-fat diet, the use of hydrolysed formulas and the protective and preventive effect of mixed or pure formulas containing fish oil as a source of lipids by parenteral administration against cholestasis and liver distress associated with intestinal failure.

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