Definition

Acute inflammatory disease in newborn intestine characterised by haemorrhagic necrosis, which may lead to perforation and destruction of the gut. Clinical presentation usually comprises triad of abdominal distension, gastrointestinal bleeding and pneumatosis intestinalis (air in bowel wall on abdominal X-ray)

Modified Bell’s criteria

Stage 1: Suspected NEC – clinical signs suggestive but X-ray non-diagnostic

• Systemic signs: 
  • temperature instability
  • apnoea
  • bradycardia
  • lethargy
• Intestinal signs: 
  • increased gastric residuals
  • abdominal distension
  • vomiting
  • blood in stools
• Radiological signs: 
  • normal/mild intestinal dilatation
  • thickened bowel loops 

Stage 2: Definite NEC – mild-to-moderately ill, abdominal X-ray demonstrates pneumatosis intestinalis and/or gas in biliary tract

• Systemic signs: see Stage 1 +/- mild metabolic acidosis, mild thrombocytopenia, raised CRP
• Intestinal signs: see Stage 1 + absent bowel sounds, +/- localised abdominal tenderness, abdominal cellulitis or right lower quadrant mass, bright red blood and/or mucus from rectum (exclude local pathology)
• Radiological signs: significant intestinal dilatation, pneumatosis intestinalis, portal vein gas, +/- ascites, persistently abnormal gas pattern (e.g. localised dilated loop of bowel seen on serial X-rays or gasless abdomen)

Stage 3: Advanced NEC – severely ill, bowel intact or perforated

• Systemic signs: see Stage 2 + hypotension, bradycardia, severe apnoea, combined respiratory and metabolic acidosis, DIC, neutropenia
• Intestinal signs: see Stage 2 + signs of generalised peritonitis, marked tenderness, distension of abdomen
• Radiological signs: see Stage 2 + pneumoperitoneum +/- ascites 

Risk factors

• Prematurity
• Intrauterine growth restriction
• Absent or reversed end-diastolic flow on umbilical arterial Doppler antenatally
• Perinatal asphyxia
• Low systemic blood flow during neonatal period (including duct-dependent congenital heart disease)
• Significant patent ductus arteriosus
• Exchange transfusion
• Formula milk
• No antenatal corticosteroids
• Infections with: Klebsiella, Enterobacter, anaerobes 

Differential diagnosis

• Sepsis with ileus
• Bowel obstruction
• Volvulus
• Malrotation
• Spontaneous intestinal perforation:
  • associated with early postnatal corticosteroids or indomethacin
  • abdominal X-ray demonstrates pneumoperitoneum but does not show evidence of pneumatosis intestinalis
• Systemic candidiasis:
  • clinical signs can mimic NEC with abdominal distension, metabolic disturbances, hypotension and thrombocytopenia
• Food protein-induced enterocolitis syndrome (FPIES)
  • usually preceded by thrombocytosis in association with formula milk
  • take thorough feeding history, and establish any temporal relationships with type of feed

Abdominal X-ray

• Supine antero-posterior view 
• If perforation suspected but not clear on supine view, left lateral view

Blood tests

• FBC: anaemia, neutropenia and thrombocytopenia often present; early return to normal carries good prognosis 
• Blood film: evidence of haemolysis and toxic changes (e.g. spherocytes, vacuolation and toxic granulation of neutrophils, cell fragments, polychromatic cells) 
• CRP, but a normal value not informative in initial phase 
• U&E 
• Blood gas: evidence of metabolic acidosis (base deficit worse than -10), raised lactate 
• Coagulation screen 
• Blood cultures 

In all stages

• Nil-by-mouth
• Transfer baby to neonatal intensive care and nurse in incubator 
• If respiratory failure and worsening acidosis, intubate and ventilate
• Gastric decompression
• Free drainage with large NGT (size 8) 
• NEC often associated with significant third space fluid loss into peritoneum
• Triple antibiotics: flucloxacillin, gentamicin and metronidazole
• IV fluids/PN: total volume ≤150 mL/kg
• Long line when stable and bacteraemia/septicaemia excluded
• Pain relief, consider morphine/diamorphine infusion (see Pain assessment and management guideline)

Stage 2: Proven NEC (confirmed radiologically)

• If breathing supported by nasal CPAP, elective intubation to provide bowel decompression (see Intubation guideline)
• Give IV fluid resuscitation sodium chloride 0.9% 10 mL/kg for shock and repeat as necessary. Shock is most common cause of hypotension in babies with NEC (see Hypotension guideline)
• If coagulation abnormal, give FFP (see Coagulopathy guideline)
• If thrombocytopenia and/or anaemia occur, transfuse (see Thrombocytopenia guideline)
• Discuss with surgical team: may need transfer to surgical centre

Stage 3 : Advanced NEC (fulminant NEC with/without intestinal perforation)

• Treat as for Stage 2 and refer to surgical team: may need laparotomy or resection of bowel in surgical centre 

In recovery phase

• In Stage 1: if improvement after 48 hr, consider restarting feeds slowly (see Nutrition and enteral feeding guideline) and stopping antibiotics
• Take into account type of milk in the context of baby’s feeding history before episode
• In Stage 2: if abdominal examination normal after 7–10 days, consider restarting feeds 
  • some may need longer period of total gut rest
  • stop antibiotics after 7–10 days
• In Stage 3: discuss with surgeon and dietitian before restarting feeds 

Late complications

• Recurrence (in about 10%)
• Strictures (in about 10% non-surgical cases)
• Short bowel syndrome and problems related to gut resection
• Neurodevelopmental delay

• Observe general condition closely and review at least 12-hrly
• Daily:
  • acid-base status
  • fluid balance (twice daily if condition unstable)
  • electrolytes (twice daily if condition unstable)
  • FBC and coagulation (twice daily if condition unstable)
  • repeat X-ray daily or twice daily until condition stable. Discuss with consultant/surgeon

• Advise parents about signs of bowel obstruction
• Medical +/- surgical follow-up after discharge
• Contrast studies if clinically indicated for strictures
• Appropriate developmental follow-up

Offer parents information on NEC, available from https://www.bliss.org.uk/parents/about-your-baby/medical-conditions/necrotising-enterocolitis-nec-a-guide-for-parents