Necrotising Enterocolitis

Introduction

Necrotizing enterocolitis (NEC) is one of the most common gastrointestinal emergencies that affects predominantly preterm infants (<37 weeks of gestation) and less commonly, term infants (>=37 weeks of gestation).

“Necrotizing” refers to death of cells and “enterocolitis” means inflammation or infection of the bowel. The spectrum of NEC is wide, ranging from early disease that resolves with medical treatment to rapidly deteriorating cases leading to death.

Infants with suspected or confirmed NEC requiring surgical assessment and / or intervention are transferred from regional hospitals to the Hong Kong Children’s Hospital (HKCH) for further management.

Causes and Risk Factors

The majority (>90%) of cases occur in very low birth weight (VLBW) infants born <1500g, or preterm infants <32 weeks gestation. It is estimated to occur in 1 to 3 per 1,000 live births, and approximately 5% of VLBW infants.

The causes of NEC are multifactorial, which include prematurity, low birth weight, congenital heart disease, and potentially intestinal microbiome abnormalities.

Signs and Symptoms

NEC can present in ill babies as well as in previously stable infants, often when they are near or at full milk feeds. Doctor may suspect NEC if your baby develops sudden changes in feeding tolerance (i.e. recurrent vomiting, increased gastric residuals) along with abdominal signs such as increased abdominal distension, blood in stool, or abnormal abdominal X-ray.

NEC is also associated with non-specific signs of illness in neonates, such as apnea (pause in breathing), desaturation (inadequate oxygen in blood) and poor perfusion (baby may look pale and blue).

In severe cases, your baby may develop sepsis (severe bacterial infection) and require mechanical ventilation and other cardiorespiratory support.

Diagnosis

NEC is a clinical diagnosis based on signs and symptoms, abdominal radiographic changes, and alterations in certain blood parameters. Abdominal radiograph is helpful to gauge the severity of NEC, by looking for evidence of stagnant loops, gaseous bubbles in the bowel wall (pneumatosis intestinalis), and / or signs of perforation of the bowel. Doctor may also order serial abdominal radiographs to track your baby’s progress.

Diagnosis of NEC can be challenging because the clinical presentation is often non-specific and difficult to differentiate from other conditions such as sepsis or preterm gut dysmotility. Currently, there are no specific blood or stool tests that can definitively diagnose NEC. Scientists and doctors are researching methods such as blood and stool markers to help diagnose NEC earlier which might help reduce serious complications associated with NEC. At HKCH, your child may be invited to participate in similar research studies.

Treatment and Management

Initial stabilization

NEC can be a life-threatening condition. Babies may have low blood pressure requiring inotropic support, lung problems requiring titration in ventilator support, and anemia and bleeding tendencies requiring blood products transfusion. Peripherally inserted central venous catheters (PICCs) are required for inotropes and later on, total parenteral nutrition. Parents will be asked to sign consent forms for blood transfusion, PICC insertion, procedural sedation, and lumbar puncture on admission.

Surgical assessment and surgery

HKCH surgeons will assess your baby upon admission. Depending on the severity of NEC, an emergency operation may be arranged. Parents will be asked to sign consent for the operation (for both surgery and anaesthesia). Initial surgery often involves removal of the gangrenous bowel, and creation of a temporary opening on the skin surface of abdomen (-ostomy) to facilitate transit of bowel contents into a stoma bag. This allows time for the remaining diseased bowel to rest.

For other babies who do not require an operation, they will usually go through 7 to 14 days of fasting and antibiotics treatment.

Some babies, though not requiring a surgery on the day of admission, may require surgical intervention during their stay in our unit, either due to change in condition or sequelae of NEC, i.e. fibrotic narrowing of the bowel lumen (stricture) during healing which leads to signs of intestinal obstruction when increasing feeds.

Feeding, nutrition and recovery

During fasting, parenteral nutrition (PN) is required to provide babies with nutrition and calories. Parenteral nutrition is administered via a peripherally inserted central venous access. After the initial period of fasting, feeding will be started gently and increased in small increments. It is important to monitor for feeding tolerance, as some babies may have post-NEC narrowing of the affected bowel (strictures) requiring elective surgery.

A common side effect of parenteral nutrition is cholestasis. Your baby’s liver function and bilirubin levels will be monitored.

We encourage parents to provide breastmilk for their babies. Our experienced nursing team will guide them through the process and give advice on milk pumping, milk storage and safe transfer to HKCH.

If your baby has an -ostomy or stoma, a second surgery is needed to close the stoma and reconnect the bowels. This surgery is usually elective and performed after the baby is tolerating full feeds and near term.

General care for term and preterm neonates

All babies in our unit will go through serial clinical assessments, blood taking, X-rays and other imaging such as cranial ultrasound scan.

In case of unstable heart and lung conditions and need of frequent blood sampling, an arterial line may be set for continuous monitoring of the baby’s blood pressure and to reduce the pain induced by peripheral venous or capillary blood sampling.

We encourage mothers to give us expressed breastmilk (EBM) in small amounts so that we can facilitate giving several drops of EBM to your baby for oral care even if your baby requires fasting (cannot take milk via tube feeds).

VLBW babies will receive retinopathy of prematurity (ROP) screening when appropriate.

Kangaroo care (skin-to-skin cuddling by parent) is known to be beneficial to the breathing pattern and brain development of infants. Our team will help to facilitate kangaroo care at bedside when your baby is stabilized.

Discharge and Follow-up

After the surgical issue is resolved, your baby will be transferred back to the referring hospital for further management or discharged to home. This depends on whether your baby still requires inpatient stay for other issues, such as tailing off ventilation and feeding training. Follow-up by HKCH Paediatric Surgery and Neonatal Team is offered to babies who received surgical intervention.

In some instances, infants with severe NEC will have short bowel syndrome requiring long term PN, and a more permanent central venous catheter will need to be placed by surgeons prior to discharge. Infants with short bowel syndrome will be arranged for our home parenteral nutrition programme with pre-discharge education on how to care for your baby, as well as joint follow-up by our Paediatric Surgery, Nutrition Support Team, Gastroenterology and / or Neonatal Team.

All VLBW infants should receive regular outpatient follow-up by the referring hospital for growth and development.

References and Useful Resources

• Children’s Hospital of Philadelphia
• NEC Society

Acknowledgement

Principal authors: Dr Hung Gi-kay Zita and Dr Lee Hoi-ying on behalf of Neonatal Team, HKCH
Initial posting: Mar 2024

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