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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 | ||||
| II. Definite | ||||
| III Advanced | ||||
| A | Temperature instability, apnoea, bradycardia | Elevated gastric residuals, mild abdominal distension, occult blood in stool | Normal or mild ileus | NPO, antibiotics x 3 days |
| B | Same as IA | Same as IA, plus gross blood in stool | Same as IA | Same as IA |
| 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 |
| 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.
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).
References
- 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
- Neu J,Walker W, Necrotising Enterocolitis, N England J Med, 2011, 364:255-264
- Neu J, Weiss MD. Necrotizing enterocolitis: Pathophysiology and prevention. J Parenteral Enteral Nutrition 1999;23:S13-7
- Caplan MS, Jilling T. New concepts in necrotizing enterocolitis. Current opinion in Pediatrics 2001;13:111-5
- Morgan J, Young L, McGuire W, Slowly advancing milk feeds does not reduce the risk of necrotising enterocolitis in very low birth weight infants Cochrane summaries, 2012
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Version history
First published: August 2013
Review by: August 2016