What is necrotising enterocolitis? 

Your little newborn baby has finally arrived, and a few days later, you notice that he/she is not eating well, vomiting, and their tummy has begun to swell. Could these signs be pointing towards a possible stomach bug or something much more serious?

Necrotising enterocolitis (NEC) is a serious medical condition where the inner lining or mucosa of the bowel becomes inflamed and damaged, often leading to perforation (rupture). Necrotising enterocolitis is the most common gastrointestinal (GI) medical/surgical emergency in newborns, more commonly referred to as “the disease of survivors”.³ This is because it is seen in premature babies (babies born before 37 weeks) who have survived other life-threatening conditions such as respiratory distress syndrome and congenital heart disease.

Sadly, around 50% of affected babies have a risk of dying from NEC, and this rate increases with prematurity.¹ The younger the gestational age of the baby, the worse the outcome becomes, and the more commonly it is seen in the hospital. It can also be observed in 10% of term and near-term babies, though it is more common in premature babies.²

Recognising the subtle clues and behaviour changes in your baby is crucial in detecting NEC, since what would appear to be an irritable baby who is not feeding well could escalate into a medical emergency in a matter of minutes to hours. 

Causes of NEC 

Causes of NEC are most likely multifactorial. However, prematurity is the greatest risk factor due to the immature gut and immunity in preterm babies. This makes the bowel of the preterm infant vulnerable to ischaemic injury and bacterial invasion, which are key processes that lead to necrotising enterocolitis.

Although they are not direct  causes of NEC, the following conditions that impair blood supply to the bowel have also been identified as risk factors:

• Sepsis
• Congenital heart disease (CHD) - a condition where babies appear to be blue because there is a defect in their heart, so not enough blood (and therefore not enough oxygen) gets around the body
• Respiratory distress syndrome (RDS) - a common breathing problem in ill premature newborns
• Perinatal asphyxia - When blood supply from the mother to the baby is disrupted, before, during or after the birth, eventually leading to poor blood supply to the guts
• Polycythaemia
• Exchange blood transfusion

 Early signs and symptoms of NEC 

Typically, a preterm neonate (newborn) would develop NEC following the first feed when the intestinal lumen becomes colonised with bacteria for the first time. This can occur in the first few days of life in term babies, but preterm babies are more likely to develop symptoms from the second week of life.

Inflammation and necrosis of the gut can occur anywhere in the intestines, but it mostly affects the distal (end) part of the small intestine and the proximal (beginning) segment of the large intestine, which would initially manifest as gastrointestinal symptoms.

These symptoms are quite subtle and can be easily missed, especially since they are not specific. This means that these symptoms can overlap with other conditions that present similarly. However, in a preterm baby, the most typical initial signs and symptoms of “classic” necrotising enterocolitis that may help differentiate it from other conditions include:

• Child refuses to feed - This is usually the first sign of NEC
• Bloating (distention) of the tummy
• Blood in stools or dark, tarry stools

Other signs include:

• Vomiting (especially green or yellow bile)
• Lethargy or reduced activity

Progression of symptoms and clinical deterioration 

Due to its rapidly progressive nature, missing signs of NEC can result in dangerous outcomes to the baby, often requiring intensive medical support, surgical intervention or even both.⁴ Therefore, it is important that you look out for the following symptoms:

• Worsening abdominal signs:
  
  • Red or discoloured abdomen
  • Visible veins or a shiny appearance
  • Firm or tender belly on touch
  • Decreased bowel sounds
    
• Systemic symptoms as an infection spreads:
  
  • Rapid breathing or difficulty breathing
  • Fever
  • Increased or unstable heart rate
  • Shock signs - low blood pressure, weak pulse
  • Poor blood supply to the peripheral tissue (cold limbs, mottled skin)
  • Apnoea (pauses in breathing, especially during sleep)
  • Bradycardia (slow heart rate)
    

If you notice that the baby is beginning to develop systemic signs in addition to the abdominal signs, it is a serious warning that urgent medical evaluation is needed.

How doctors diagnose NEC 

NEC is diagnosed by Bell’s scoring system, which will classify the severity of the condition from mild to advanced NEC based on clinical signs, symptoms and X-Ray features.⁶

This is an important tool which guides doctors in accurately diagnosing and formulating an effective treatment plan individualised to the baby.

FAQs

Who is most at risk?

• Premature infants
• Babies with low birth weight <1500 g  - fatality rate is between 10-20%. The higher the birth weight, the higher the risk of NEC¹
• Formula feeding - Preterm infants fed cow’s milk formula are more likely to develop this condition than those fed only breast milk. However, NEC can also develop in term neonates who have never been orally fed.⁸ This is most likely because breast milk contains a more natural balance of sugars that promote the growth of beneficial bacteria in the babies’ guts as well as protective factors such as IgA antibodies that prevent harmful bacteria from adhering to the intestinal lining. These compounds work together to maintain a healthy balance of gut microflora (ecosystem of bacteria)
• Large-volume milk feedings that are increased too rapidly during feeding schedules may place undue stress on a previously injured or immature intestine
• Neonates in NICUs (neonatal intensive care units) with certain risk factors (such as use of feeding tubes or infections)

How does NEC occur?

While the exact cause of NEC is generally poorly understood, risk factors are believed to be associated with a triad of underlying factors:⁵

• Intestinal ischemia - Any event which decreases blood supply to the bowel, weakening the bowel wall and increasing the risk of perforation
• Enteral feeding - The premature gut has decreased motility (flexibility) and function, causing inadequate passage and accumulation of food, which may create an ideal environment for gut bacteria to thrive and cause damage to the gut
• Gut microflora - The underdeveloped gut-blood barrier and immunity in pre-term babies allow gut bacteria to invade the bowel wall and enter the blood, causing widespread infection

What happens if the baby develops NEC?

1. The baby will be on a ten-day antibiotic course consisting of three antibiotics to eradicate any harmful gut bacteria
2. Vigilant monitoring of the baby’s condition will be done by various blood tests and X-rays
3. X-ray imaging will be used to detect any signs of perforation, which might need surgery
4. The stomach contents are emptied using a tube that goes from the baby’s nose or mouth into the stomach (nasogastric or orogastric tube)
5. The method of nutrition will be changed from milk to a fluid called Total Parenteral Nutrition (TPN). It contains a mix of essential nutrients such as carbohydrates, fats and proteins, which are fed through a drip line inserted into the veins of the arms or neck. The main aim of doing this is to allow the bowel to rest

How do you prevent NEC?

• Avoiding cow-milk-based products and continuing breastfeeding, especially in the first few weeks of birth, reduces the risk of NEC in babies⁵
• Ensuring that oral feeding is controlled by feeding small amounts of expressed breast milk instead of aggressive feeding in large amounts⁶
• Using probiotics, such as yoghurt and other dairy products, helps in improving the gut microflora by increasing the number of gut-friendly bacteria. However, its efficacy is still being studied⁷
• Administering corticosteroids to the mother before delivery enhances the baby’s lung maturity, thereby decreasing the chance of respiratory distress and NEC

Summary

Necrotising enterocolitis (NEC) is the most common gastrointestinal (GI) emergency in neonatal intensive care units (NICUs), making it one of the leading causes of long-term disability in preterm infants.

Despite the advancements in care, NEC continues to have a high mortality rate due to its tendency to rapidly escalate to a severe, life-threatening condition. Therefore, being aware of these warning signs can make a life-saving difference for vulnerable babies.