Key Facts

NEC is the most common surgical emergency in neonatal intensive care. It has high mortality and significant long-term morbidity. Prevention through breast milk feeding and probiotic supplementation is increasingly emphasised.

Epidemiology

NEC affects 5-10% of VLBW infants (<1500g). Overall incidence in NICU admissions is ~2-5%. Mortality is 20-30% overall and up to 50% in those requiring surgery. NEC is more common in formula-fed infants and those with PDA.

Aetiology

NEC is multifactorial:

• Prematurity: Immature gut mucosal barrier, motility, and immune function
• Enteral feeding: Formula feeding increases risk; breast milk is protective
• Ischaemia: Perinatal asphyxia, low-flow states (PDA, cardiac defects)
• Infection: Gut colonisation with pathogenic bacteria
• Iatrogenic: Umbilical catheters, indometacin/ibuprofen for PDA

Pathophysiology

NEC results from a combination of gut mucosal immaturity, abnormal bacterial colonisation, and an exaggerated inflammatory response. The immature gut barrier allows bacterial translocation, triggering a pro-inflammatory cascade (TNF-α, IL-6, PAF) leading to mucosal necrosis. This progresses from superficial mucosal injury to full-thickness bowel wall necrosis, perforation, peritonitis, and septic shock.

Clinical Features

• Feeding intolerance: Increased gastric aspirates, vomiting (bile-stained)
• Abdominal distension: Progressive; tender; erythema of abdominal wall (late)
• Bloody stools: Frank blood or occult blood positive
• Systemic signs: Apnoeas, bradycardias, temperature instability, lethargy, metabolic acidosis, hypotension, DIC

Bell Staging

• Stage I (Suspected): Feeding intolerance, mild distension, occult blood in stool; non-specific systemic signs
• Stage II (Definite): Gross blood in stool, marked distension, absent bowel sounds; pneumatosis on AXR
• Stage III (Advanced): Perforation, peritonitis, shock, DIC; pneumoperitoneum on AXR

Red Flags

• Fixed dilated bowel loop on serial AXR — suggests full-thickness necrosis
• Portal venous gas — severe NEC
• Pneumoperitoneum — perforation; needs urgent surgery
• Rapidly worsening metabolic acidosis and thrombocytopenia — fulminant NEC
• Abdominal wall erythema — transmural necrosis

Bedside

• Observations: HR, RR, SpO2, BP, temperature — sepsis screen
• Abdominal examination: Distension, tenderness, erythema, absent bowel sounds

Bloods

• FBC: Thrombocytopenia (poor prognosis indicator), neutropenia or neutrophilia
• CRP: Elevated (serial monitoring)
• Blood gas: Metabolic acidosis (raised lactate, low pH, low bicarbonate)
• Blood culture: Before starting antibiotics
• Coagulation: DIC screen (PT, APTT, fibrinogen, D-dimer)
• U&Es, glucose: Metabolic derangement

Imaging

• AXR (supine and lateral decubitus): Key investigation
  • Dilated bowel loops
  • Pneumatosis intestinalis (intramural gas — pathognomonic)
  • Portal venous gas (branching lucencies over liver)
  • Pneumoperitoneum (free air = perforation)
  • Fixed dilated loop on serial films (failed to change position)
• USS abdomen: May show free fluid, thickened bowel wall, absent peristalsis, portal venous gas

Special Tests

• Serial AXR: 6-12 hourly in acute phase — track progression
• Stool culture: If infective cause suspected

Medical (Stage I-II)

• Nil by mouth: For 7-14 days depending on severity
• NGT on free drainage: Decompress stomach
• IV antibiotics: Triple therapy — per local protocol (e.g., amoxicillin/ampicillin + gentamicin + metronidazole) for 7-14 days
• TPN: Nutritional support during bowel rest
• IV fluids: Resuscitation with 0.9% NaCl boluses (10-20mL/kg)
• Blood products: Platelets if <50, FFP if DIC, pRBC if anaemic
• Inotropes: If cardiovascular compromise despite fluid resuscitation
• Serial AXR: 6-12 hourly during acute phase

Surgical (Stage III or Failed Medical)

• Indications: Pneumoperitoneum (perforation), clinical deterioration despite medical treatment, fixed dilated bowel loop, abdominal wall cellulitis
• Procedures: Laparotomy with resection of necrotic bowel ± stoma formation; or primary peritoneal drainage (PD) in very small/unstable infants
• Stoma reversal: Usually 6-12 weeks later when recovered

Prevention

• Breast milk feeding: Reduces NEC by ~50% — maternal EBM or donor human milk
• Probiotics: Growing evidence for NEC prevention in preterm infants (Lactobacillus, Bifidobacterium); used in many UK NICUs
• Cautious enteral feeding advancement: Standardised feeding protocols reduce NEC incidence
• Avoid unnecessary antibiotics: Prolonged empirical antibiotics increase NEC risk

Referral Criteria

• All suspected NEC — neonatal surgical team consultation
• Pneumoperitoneum — emergency surgery
• Clinical deterioration despite medical management — surgical review

• Overall mortality: 20-30%; higher in surgical NEC (~50%)
• Short bowel syndrome: Affects ~10-25% of surgical survivors; may need long-term TPN
• Strictures: ~20-30% post-NEC — may present weeks later with obstruction
• Neurodevelopmental impairment: Increased risk compared with gestational age-matched controls without NEC
• Recurrence: ~5-10% in medically managed NEC

Bell Staging of NEC

AXR Findings in NEC