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Key messages

  • The incidence of necrotising enterocolitis (NEC) is inversely proportional to birthweight. In general, the age of onset is inversely proportional to gestation; therefore smaller babies present later.
  • Babies with definite NEC should be referred to a Level 6 neonatal unit.
  • Ninety per cent of babies with NEC are preterm.
  • The mortality rate of NEC is 20-40 per cent.

Please note that all guidance is currently under review and some may be out of date. We recommend that you also refer to more contemporaneous evidence in the interim.

Necrotising enterocolitis (NEC) is when sections of the bowel tissue die. 

NEC is the most common gastrointestinal (GI) emergency in neonates and can present late in tiny babies.

Early or suspected NEC is difficult to diagnose; if in doubt treat early and conservatively (nil by mouth and broad-spectrum antibiotics).

Necrotising enterocolitis issues

Points to note about incidence and mortality rates for NEC:

  • Ninety percent of babies with NEC are preterm.
  • NEC is predominantly a disease of the very low birthweight infant and is most common in babies < 1000 g or those that are both preterm and growth-restricted.
  • The incidence of NEC is inversely proportional to birthweight. In general, the age of onset is inversely proportional to gestation; therefore smaller babies present later.
  • The mortality rate of NEC is 20-40 per cent, with the highest rate among those that require surgery (approximately 50 per cent). Of those who survive, approximately 25 per cent develop long-term sequelae.
  • Early or suspected NEC is often difficult to diagnose as the clinical signs and symptoms are often non-specific, as are the radiological and laboratory findings.

As babies with definite NEC should be transferred to a Level 6 Neonatal unit, this topic will concentrate mainly on the presentation and diagnosis of NEC as well as the special care nursery (SCN) management of a baby who has had previous NEC.

Risk factors for NEC

Risk factors for NEC include:

  • prematurity
  • enteral feeding (although approx. 10 per cent of cases occur in infants never fed)
  • formula feeding (six times more common than if only breast-milk fed)
  • often occurs in clusters (although organisms vary)
  • bowel ischaemia
  • in term infants
    • polycythaemia
    • cardiac surgery
    • abdominal surgery (especially gastroschisis, intestinal atresia)
    • endocrine abnormalities.

Clinical presentation

Clinical signs and symptoms are highly variable but include:

  • GI dysfunction:
    • abdominal distention, tenderness
    • vomiting, often bilious
    • feed intolerance, with increased aspirates from enteral feeding tubes (may be bilious)
    • blood in stool.
  • Systemic:
    • temperature instability
    • apnoea and/or bradycardia
    • lethargy
    • hypotension
    • acidosis.
  • The severity, radiology and management of NEC are best exemplified by the ‘Modified Bell’s staging criteria’.

Modified Bell’s staging criteria for NEC

 Stage Systemic signs Intestinal signs Radiological signs  Treatment
I. Suspected 

Temperature instability, apnoea, bradycardia

Elevated gastric residuals, mild abdominal distension, occult blood in stool

Normal or mild ileus

NPO, antibiotics x 3 days


Same as IA

Same as IA, plus gross blood in stool

Same as IA

Same as IA

II. Definite

A: Mildly ill

Same as IA

Same as I, plus absent bowel sounds, abdominal tenderness

Ileus, pneumatosis intestinalis

NPO, antibiotics x 7-10 days

B: Moderately ill

Same as I, plus mild metabolic acidosis, mild thrombocytopenia

Same as I, plus absent bowel sounds, definite abdominal tenderness, abdominal cellulitis, right lower quadrant mass

Same as IIA, plus portal vein gas, with or without ascites

NPO, antibiotics x 14 days

III Advanced

A: Severely ill, bowel intact

Same as IIB, plus hypotension, bradycardia, respiratory acidosis, metabolic acidosis, disseminated intravascular coagulation, neutropenia

Same as I and II, plus signs of generalised peritonitis, marked tenderness and distension of abdomen.

Same as IIB, plus definite ascites

NPO, antibiotics x 14 days, fluid resuscitation, inotropic support, ventilator therapy, paracentesis

B: Severely ill: bowel perforated 

Same as IIIA

Same as IIIA

Same as IIB, plus pneumoperitoneum

Same as IIA, plus surgery

NB: Permission to use the Modified Bell's staging criteria has been given by Paediatrics in Review. 

Modified Bell's staging criteria

Differential diagnosis of suspected NEC

When performing a differential diagnosis consider:

  • dysmotility of prematurity
  • septic ileus
  • bowel obstruction
  • gastroenteritis
  • anal fissure
  • cow’s milk protein-sensitive enterocolitis. 

Radiographic findings

Non-specific signs

Non-specific signs for NEC include:

  • diffuse gaseous distension
  • asymmetric, disorganised bowel pattern
  • ‘featureless’ loops
  • dilated bowel loops
  • bowel wall thickening
  • increased peritoneal fluid.

Diagnostic signs

Diagnostic signs for NEC include:

  • persistent loop
  • pneumatosis intestinalis (virtually pathognomonic):
    • submucosal bubbly or cystic appearance (may be confused with stool, although stool usually moves on serial x-rays)
    • subserosal linear or curvilinear appearance
  • portal venous gas
  • pneumoperitoneum (although may not be due to NEC).

Management of NEC

Management of NEC includes:

  • see ‘Modified Bell’s staging criteria’ table for duration
  • nil by mouth
  • gastric tube on free drainage
  • blood culture
  • antibiotics
    • vancomycin
    • gentamicin
    • metronidazole (only for definite NEC)
  • cases of definite NEC should be referred to PIPER for consultation on management, as the following (may be) required:
    • gut rest for 10-14 days
    • total parenteral nutrition (TPN)
    • fluid management
    • inotropes
    • ventilation
    • analgesia
    • frequent radiographs
    • surgery (25-50 per cent of cases).

Complications of NEC

Complications of NEC may include:

  • Surgery requiring ileostomy:
    • require supplemental sodium even when well
    • high risk of rapid dehydration with gastroenteritis.
  • Stricture:
    • 20-30 per cent
    • most commonly in large bowel
    • 80 per cent on left side
    • may not develop for weeks to months post-NEC
    • presents with recurrent abdominal distension
    • surgical consultation and contrast enema required.

Prevention of NEC

Preventative strategies include:

  • antenatal corticosteroids
  • early intervention (nil orally) for suspected NEC
  • breast milk
  • infection control practices may limit the size of disease clusters.

Areas of uncertainty 

Areas of uncertainty in clinical practice include:

  • effect of rate of feed upgrade in the prevention of NEC
  • prophylactic antibiotics (proven to reduce NEC risk but concern regarding development of antibiotic-resistant organisms)
  • administration of probiotics
  • enteral IgA (enteral IgG refuted).


  • Taeusch HW, Ballard RA. Avery’s Diseases of the Newborn 7th edn. W.B. Saunders Company, Philadelphia. 1998
  • Chandler JC, Hebra A. Necrotizing enterocolitis in infants with very low birth weight. Sem Pediatr Surg 2000;9:63-72
  • Buonomo C. The radiology of necrotizing enterocolitis. Radiol Clinics North Amer 1999;37:1187-98

Other reading

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Centre of Clinical Excellence - Women and Children
Safer Care Victoria

Version history

First published: August 2013

Last web update: October 2018

Review by: October 2019

Uncontrolled when downloaded

Page last updated: 17 Feb 2021

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