Necrotising enterocolitis (NEC)

What is it?

Necrotising enterocolitis (NEC) is a condition where the bowels (intestines) become infected and inflamed. “Necrotizing” means the death of tissue, “entero” refers to the small intestine, “colo” to the large intestine, and “itis” means inflammation.

Why does it occur?

Most cases of NEC occur in premature babies, typically within the first 2-3 weeks of life and usually after the baby starts receiving milk feeds. The exact cause is not clear, but it seems to occur when a baby’s immune and digestive systems have not yet properly developed. An immature gut may have difficulty absorbing milk. If a baby’s intestines are weak due to low oxygen (due to the body prioritising oxygen to other parts of the body) or poor blood flow, then the stress of food moving through it may result in bacteria that would normally not cause any problems invading and damaging the walls of the intestine. In addition, a premature baby’s immune system may not be able to deal with the resulting infection.

NEC is less common in babies who are fed expressed breast milk rather than formula, possibly due to the anti-bacterial and anti-inflammatory properties of human breast milk.

Why is it a problem?

If a NEC infection becomes severe, it can cause serious damage to or holes in the intestines, and/or infection of the blood or the membrane lining the abdomen. This can be life-threatening in a tiny baby with an immature immune sytem. Even when a case of NEC is mild, doctors must stop milk feeds until the infection clears up, resulting in a baby failing to gain weight at a critical time in its life.

The lower the birth weight and earlier the gestational age of a premature baby, the more likely they are to develop NEC, and the higher their chances of dying from it.

How is it treated?
For babies who have mild to moderate NEC, treatment usually consists of
- “nil by mouth” - stopping milk feeds and using intravenous feeds (ie through a vein) while the bowel recovers
- a course of antibiotics, and
- removing extra fluids and gas from the intestine via a naso- or orogastric tube.
This treatment usually lasts between 3 and 10 days.

If the baby’s abdomen is so swollen that it interferes with breathing, extra oxygen or a ventilator may be used to help the baby breathe. If the baby does not improve with treatment, or if he or she gets a hole in their intestines, it may be necessary to use surgery to remove damaged parts of the intestines.

Unfortunately NEC is difficult to diagnose quickly, as the earliest symptoms can be quite general (eg apnoea and bradycardia, temperature instability) and vary depending on how severe the condition is. Later symptoms include a swollen belly. A diagnosis of NEC is usually confirmed via x-ray (showing air bubbles in the intestines) and blood tests.

Hospital staff try to minimise the risk of a baby contracting NEC by carefully regulating the amount of milk a baby receives, increasing the volume of milk slowly, encouraging mothers to express milk for their baby, and maintaining strict hygiene standards in the NICU.

Are there ongoing complications?

Most babies who develop NEC recover fully and do not have further feeding problems, but in some cases, scarring of the bowel may occur, particularly if surgery was required. This can lead to future problems such as malabsorption (the inability of the bowel to absorb nutrients normally).

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This is one of a series of articles I’ve written for the L’il Aussie Prems newsletter under the heading of Premmie Health. Read my disclaimer here.