Necrotising Enterocolitis (NEC)

1. Clinical Overview

Summary

Necrotising Enterocolitis (NEC) is the most common and devastating gastrointestinal emergency affecting neonates, characterised by intestinal inflammation progressing to ischaemic necrosis, perforation, and systemic sepsis. [1,2] It primarily affects preterm infants, with the disease representing a complex interplay between intestinal immaturity, abnormal bacterial colonisation, and inflammatory dysregulation triggered by enteral feeding substrates. [3]

The pathogenesis involves an inappropriate inflammatory response to commensal bacteria in the setting of an immature intestinal barrier, leading to activation of toll-like receptor 4 (TLR4) signalling pathways and subsequent mucosal injury. [4,5] Despite advances in neonatal care, NEC remains a leading cause of morbidity and mortality in very low birth weight (VLBW) infants, with mortality rates of 20-30% overall and up to 50% in those requiring surgical intervention. [1,6]

Key Facts

Clinical Pearls

The "Fixed Loop" Sign: A dilated bowel loop that remains in the same position on serial abdominal radiographs taken 6-8 hours apart indicates paralysed, likely necrotic bowel. This finding has high specificity for surgical disease. [12]

The Platelet Sentinel: A sudden drop in platelet count below 100 × 10⁹/L in a preterm infant with abdominal distension is NEC until proven otherwise. Thrombocytopenia develops due to platelet consumption in the necrotic intestinal vasculature and disseminated intravascular coagulation. [13]

The "Watershed" Vulnerability: The terminal ileum and proximal colon are most commonly affected (75-80% of cases) due to their watershed blood supply between the superior and inferior mesenteric arteries. [14]

NEC is a "Disease of the Growing Feeder": 90-95% of NEC cases occur in infants who have been enterally fed. The remaining 5-10% represent a distinct "early NEC" phenotype often associated with congenital heart disease or severe perinatal hypoxia. [3,9]

Why This Matters Clinically

NEC is unpredictable and can progress from subtle feeding intolerance to fulminant intestinal necrosis within 12-24 hours. Prevention through breast milk, standardised feeding protocols, and judicious use of probiotics represents the most effective strategy, as treatment options are limited to supportive care and surgical debridement. Survivors face significant long-term complications including short bowel syndrome (25-35%), neurodevelopmental impairment (25-45%), and intestinal strictures (15-35%). [1,11,15]

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2. Epidemiology

Incidence and Prevalence

NEC is the most common gastrointestinal emergency in neonates, with incidence inversely proportional to gestational age and birth weight. [7] Geographical and temporal variation exists, with outbreaks suggesting potential infectious aetiology in some cases.

Risk Factor Analysis

The development of NEC requires a confluence of risk factors affecting the immature intestinal barrier, the intestinal microbiome, and the inflammatory response. [3,4]

Major Risk Factors (Strong Evidence)

Moderate Risk Factors

Transfusion-Associated Gut Injury (TRAGI)

A specific entity where NEC develops within 24-48 hours of red blood cell transfusion, occurring in approximately 25-35% of NEC cases in VLBW infants. [20]

Proposed Mechanisms:

1. Pre-transfusion Anaemia: Chronic tissue hypoxia with compensatory vasodilation
2. Reperfusion Injury: Sudden increase in oxygen delivery and viscosity
3. Inflammatory Mediators: Stored blood contains pro-inflammatory cytokines
4. Nitric Oxide Scavenging: Free haemoglobin from haemolysis

Current Practice:

• Some centres withhold feeds during transfusion in high-risk infants (less than 28 weeks)
• Evidence remains inconclusive; large RCTs ongoing [20]
• Restrictive transfusion thresholds may reduce TRAGI risk

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3. Pathophysiology

The Pathophysiological Triad

NEC develops from the interaction of three essential elements in the vulnerable preterm intestine. [1,3,4]

┌─────────────────────────────────────────────────────────────────────┐
│                     PATHOPHYSIOLOGY OF NEC                          │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│    ┌───────────────┐                        ┌───────────────┐      │
│    │   IMMATURE    │                        │   ABNORMAL    │      │
│    │   INTESTINE   │◄──────────────────────►│  MICROBIOME   │      │
│    │               │                        │               │      │
│    │ • TLR4 upregulation                   │ • Dysbiosis   │      │
│    │ • Weak tight junctions                │ • Proteobacteria     │
│    │ • Low IgA/defensins                   │ • Reduced diversity  │
│    │ • Impaired peristalsis                │ • Pathogen bloom     │
│    └───────┬───────┘                        └───────┬───────┘      │
│            │                                        │              │
│            │         ┌──────────────┐              │              │
│            └────────►│   ENTERAL    │◄─────────────┘              │
│                      │   FEEDING    │                              │
│                      │              │                              │
│                      │ • Substrate for fermentation               │
│                      │ • Mucosal stress                           │
│                      │ • Formula vs breast milk                   │
│                      └──────┬───────┘                              │
│                             │                                      │
│                             ▼                                      │
│                   ┌─────────────────┐                              │
│                   │   INFLAMMATORY  │                              │
│                   │    CASCADE      │                              │
│                   │                 │                              │
│                   │ TLR4 → NF-κB → TNF-α, IL-1β, IL-6             │
│                   │ → Mucosal injury → Translocation              │
│                   │ → Pneumatosis → Necrosis → Perforation        │
│                   └─────────────────┘                              │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘

3.1 Intestinal Immaturity

The preterm intestine differs fundamentally from the mature gut in ways that predispose to NEC. [4,5]

Barrier Dysfunction

The TLR4 Hypothesis

Toll-like receptor 4 (TLR4) is the central molecular mediator in NEC pathogenesis. [4,5]

Developmental Role:

• In utero, TLR4 promotes intestinal development and epithelial differentiation
• Amniotic fluid and breast milk contain TLR4-inhibiting factors

Pathological Activation:

• After birth, TLR4 binds bacterial lipopolysaccharide (LPS/endotoxin)
• In the immature gut, TLR4 is paradoxically upregulated (unlike adults)
• Activation triggers NF-κB pathway → pro-inflammatory cytokines
• Results in epithelial apoptosis, reduced blood flow, and mucosal breakdown

Downstream Effects:

1. Endothelial Dysfunction: Reduced nitric oxide synthesis → vasoconstriction
2. Epithelial Apoptosis: Direct TLR4-mediated cell death
3. Impaired Repair: TLR4 inhibits enterocyte migration and proliferation
4. Inflammatory Amplification: Neutrophil recruitment, reactive oxygen species

3.2 Abnormal Bacterial Colonisation (Dysbiosis)

The intestinal microbiome differs dramatically between healthy term infants and those who develop NEC. [3,22]

Microbiome Comparisons

The "Proteobacterial Bloom"

Studies demonstrate a characteristic expansion of Gammaproteobacteria (particularly Enterobacteriaceae) in the 1-2 weeks preceding NEC onset. [22]

Contributing Factors to Dysbiosis:

1. Prolonged Antibiotics: Eliminates protective commensals
2. Formula Feeding: Lacks human milk oligosaccharides (HMOs)
3. NICU Environment: Cross-colonisation with resistant organisms
4. Delayed Enteral Feeding: Prolonged TPN, reduced substrate for beneficial bacteria
5. H2 Blockers/PPIs: Reduced gastric acid barrier

3.3 Ischaemia-Reperfusion Injury

The intestine is exquisitely sensitive to hypoxia due to its high metabolic demands and countercurrent oxygen exchange in the villi. [3,14]

The "Diving Reflex" Concept

During hypoxic or hypovolaemic stress, blood flow is preferentially redistributed away from the splanchnic circulation to vital organs (brain, heart, adrenals).

Phases of Injury:

1. Ischaemia Phase: ATP depletion, cellular swelling, anaerobic metabolism
2. Reperfusion Phase: Paradoxically causes more damage than ischaemia
   • Reactive oxygen species generation
   • Neutrophil recruitment and activation
   • Complement activation
   • Nitric oxide-peroxynitrite cascade

Vulnerable Regions:

• Terminal ileum (watershed between SMA and IMA territories)
• Splenic flexure (watershed between SMA and IMA)
• Rectosigmoid junction (watershed between IMA and internal iliac)

3.4 The "Term NEC" Phenotype

NEC in term infants represents a distinct entity with different pathophysiology. [8]

Common Associations with Term NEC:

• Congenital heart disease (especially left-sided obstructive lesions)
• Polycythaemia/hyperviscosity
• Birth asphyxia
• Exchange transfusion
• Cocaine/amphetamine exposure in utero

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4. Classification: Bell's Staging Criteria

The Modified Bell's Staging System remains the gold standard for NEC classification, guiding diagnosis and management. [23]

Modified Bell's Staging System

Radiological Findings: Detailed Interpretation

Pathognomonic Signs

1. Pneumatosis Intestinalis (Intramural Gas)

• Gas within the bowel wall, produced by bacteria invading submucosa
• Appears as linear or cystic lucencies along the bowel wall
• "Railroad tracks" (linear) or "soap bubbles" (cystic)
• Highly specific for NEC (Sensitivity 44-100%, Specificity 96-100%) [12]

2. Portal Venous Gas (Hepatic Portal Venous Gas)

• Branching linear lucencies over the liver shadow
• Indicates gas has tracked from gut → mesenteric veins → portal vein
• Ominous sign: associated with 33-50% mortality
• Differentiater from biliary air (more central, doesn't reach periphery) [12]

3. Pneumoperitoneum (Free Air)

• Football Sign: Large central lucency with visible falciform ligament
• Rigler's Sign: Both sides of bowel wall visible (double wall sign)
• Lateral Decubitus View: Most sensitive for detecting small amounts
• Indicates perforation requiring surgical intervention [12]

Secondary Signs

Staging Transition and Deterioration Markers

Signs of Progression:

• Increasing abdominal girth (> 2 cm in 4-6 hours)
• Falling platelet count (drop > 50% or less than 100 × 10⁹/L)
• Worsening metabolic acidosis (base deficit > 10 mEq/L)
• Rising lactate (> 4 mmol/L)
• Oliguria (less than 1 mL/kg/h)
• New pneumatosis or portal venous gas on imaging
• Fixed bowel loop on serial radiographs

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5. Clinical Presentation

Early Warning Signs (Subtle Phase)

Early NEC often presents with non-specific signs that precede obvious intestinal disease by 12-24 hours. [1,9]

Classical Presentation (Established Phase)

Late Signs (Surgical Phase)

Physical Examination Approach

Systematic Abdominal Assessment:

1. Inspection: Distension, skin changes, visible loops, umbilical discharge
2. Auscultation: Bowel sounds (absent = ileus, high-pitched = obstruction)
3. Percussion: Tympany (gas), dullness (fluid/mass)
4. Palpation: Tenderness, guarding, rigidity, masses

Abdominal Girth Monitoring Protocol:

• Measure at umbilical level, same position each time
• Document every 4-6 hours in acute phase
• Increase of > 2 cm suggests progression
• Mark measurement point with skin marker for consistency

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6. Investigations

First-Line Investigations

Abdominal Radiograph Protocol

Frequency:

• Stage I: Every 12 hours
• Stage II: Every 6-8 hours
• Stage III: Every 4-6 hours or with any clinical change

Views:

• Supine AP: Standard view, assess bowel gas pattern
• Left Lateral Decubitus: Most sensitive for free air (air rises to right side)
• Cross-table Lateral: Alternative for free air detection

Systematic Interpretation (ABCDEFG):

• Air pattern: Distribution, dilated loops, fixed loops
• Bowel wall: Thickness, pneumatosis (linear/cystic)
• Calcifications: Unusual but may indicate perforation
• Displacement: Mass effect, ascites separating loops
• Extraluminal air: Pneumoperitoneum, retroperitoneal air
• Free fluid: Haziness, loss of psoas shadow
• Gas in unusual places: Portal venous gas, abscess

Abdominal Ultrasound

Increasingly used as adjunct to radiography, with advantages of no radiation and real-time assessment. [12]

Diagnostic Paracentesis

Indications:

• Clinical deterioration despite maximum medical therapy
• Uncertainty about perforation
• Significant ascites (may need drainage for respiratory distress)

Positive Findings:

• Brown/feculent fluid → Perforation (indication for surgery)
• Gram-positive or gram-negative organisms on gram stain
• WBC > 500/mm³
• Elevated lactate in fluid

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7. Management

Management Overview by Bell's Stage

┌─────────────────────────────────────────────────────────────────────┐
│                    NEC MANAGEMENT ALGORITHM                         │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│  STAGE I (SUSPECTED)                                               │
│  ├── NPO for 48-72 hours                                           │
│  ├── IV fluids (maintenance + deficit)                             │
│  ├── Broad-spectrum antibiotics                                    │
│  ├── Serial examinations (Q4-6h)                                   │
│  ├── Serial AXR (Q12h)                                             │
│  └── If resolves: Slow refeeding after 48-72h                      │
│                                                                     │
│  STAGE II (DEFINITE)                                               │
│  ├── NPO for 7-14 days                                             │
│  ├── TPN initiation (protein, lipids, micronutrients)              │
│  ├── Triple antibiotics (Amp + Gent + Metro)                       │
│  ├── NG decompression (free drainage)                              │
│  ├── Surgical consultation                                         │
│  ├── Serial AXR (Q6-8h)                                            │
│  ├── Platelet/FFP if coagulopathic                                 │
│  └── Monitor: Girth, platelets, pH, lactate                        │
│                                                                     │
│  STAGE III (ADVANCED)                                              │
│  ├── All Stage II measures                                         │
│  ├── Intensive care level support                                  │
│  ├── Inotropic support (Dopamine/Dobutamine/Adrenaline)            │
│  ├── Mechanical ventilation if required                            │
│  ├── Blood products (PRBC, platelets, FFP, cryoprecipitate)        │
│  ├── Paracentesis if large ascites                                 │
│  └── SURGERY if: Pneumoperitoneum, positive paracentesis, or       │
│       clinical deterioration despite maximal medical therapy        │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘

7.1 Medical Management

Gastrointestinal Rest

Nil Per Os (NPO):

• Stage IA/IB: 48-72 hours minimum
• Stage IIA: 7-10 days
• Stage IIB/IIIA: 10-14 days minimum
• Post-surgical: Until anastomosis healed or stoma functioning

Nasogastric Decompression:

• Large bore tube (8-10 Fr) on free drainage or low intermittent suction
• Prevents further gaseous distension
• Reduces risk of aspiration
• Document output (blood, bile)

Antimicrobial Therapy

Standard Triple Therapy Rationale:

Alternative Regimens:

• Meropenem monotherapy: 20-40 mg/kg Q8h if ESBL concerns or renal impairment
• Vancomycin + Gentamicin + Metronidazole: If MRSA/CoNS suspected
• Piperacillin-Tazobactam + Metronidazole: Broad-spectrum alternative

Duration:

• Stage I: 3-5 days (if cultures negative, clinical resolution)
• Stage II: 7-14 days
• Stage III: Minimum 14 days, guided by clinical response

Fluid and Haemodynamic Support

Fluid Management:

• Significant third-spacing occurs; often need 1.5-2× maintenance
• Monitor urine output (target > 1 mL/kg/h)
• Correct hyponatraemia with sodium supplementation (not water restriction)
• Daily weights, strict input/output documentation

Cardiovascular Support:

• First-line: Volume resuscitation (10-20 mL/kg crystalloid boluses)
• Inotropes if persistent hypotension:
  • Dopamine 5-15 mcg/kg/min
  • Dobutamine 5-20 mcg/kg/min (if poor cardiac output)
  • Adrenaline 0.05-0.5 mcg/kg/min (refractory shock)
• Hydrocortisone 1 mg/kg Q8h for inotrope-resistant shock

Blood Product Transfusion

7.2 Nutritional Management (TPN)

TPN Prescription Framework:

Lipid Formulation:

• SMOF lipids (Soy, MCT, Olive, Fish oil) preferred over pure soy-based
• Fish oil component (omega-3) reduces intestinal failure-associated liver disease (IFALD)
• Monitor triglycerides weekly (target less than 250 mg/dL)

7.3 Surgical Management

Absolute Indications for Surgery

1. Pneumoperitoneum (free air on X-ray)
2. Positive Paracentesis (brown/feculent fluid, bacteria on gram stain)

Relative Indications for Surgery

• Clinical deterioration despite maximal medical therapy
• Fixed bowel loop on serial radiographs (> 24-36 hours)
• Abdominal wall erythema or discolouration
• Palpable abdominal mass
• Worsening acidosis (pH less than 7.25, lactate > 4 mmol/L persistently)
• Inotrope-dependent shock

Surgical Options

1. Primary Peritoneal Drainage (PPD)

Indications:

• ELBW infants (less than 1000g) too unstable for laparotomy
• As temporising measure before definitive surgery
• Occasionally definitive therapy in selected cases

Technique:

• Bedside procedure under local anaesthesia
• Penrose drain placed in right lower quadrant
• Allows drainage of peritoneal contamination
• Can reassess need for laparotomy after stabilisation

Outcomes:

• Definitive in ~30-50% of cases
• Others require subsequent laparotomy
• No clear survival advantage over primary laparotomy [24]

2. Exploratory Laparotomy

Standard Approach:

• Right transverse supraumbilical incision (muscle-cutting)
• Evacuate "dishwater" purulent fluid
• "Run" bowel from ligament of Treitz to rectum
• Assess viability: Pink = viable; Purple = questionable; Black = necrotic

Surgical Decision Tree:

Intraoperative Findings → Decision
├── Focal necrosis (clear demarcation)
│   └── Resection + Primary Anastomosis (if stable) OR Stoma
├── Multifocal necrosis (patchy areas)
│   └── Resection of frankly necrotic bowel + Multiple stomas
│       OR "Clip and Drop" with planned second-look
├── Extensive questionable bowel
│   └── Conservative resection + Second-look laparotomy at 24-48h
└── Pan-intestinal necrosis (> 75-90% bowel)
    └── Consider palliative care (family discussion)

3. Second-Look Laparotomy

Indications:

• Bowel viability uncertain at initial surgery
• "Damage control" approach with clip and drop

Timing:

• Typically 24-48 hours after initial surgery
• Allows haemodynamic stabilisation
• Bowel "declares itself"
• purple becomes pink (viable) or black (necrotic)

Benefits:

• Preserves maximal bowel length
• Avoids unnecessary resection of viable bowel
• Reduces risk of short bowel syndrome

Stoma Considerations

Stoma Types:

• Jejunostomy (high output, significant fluid/electrolyte losses)
• Ileostomy (most common, moderate output)
• Colostomy (lower output, easier management)

Management Challenges:

• High-output stomas require sodium supplementation (4-6 mmol/kg/day)
• Skin breakdown from corrosive effluent (barrier creams, stoma appliances)
• May need stoma feeds (mucous fistula refeeding)

Reversal:

• Typically when baby > 2 kg and thriving
• Usually 6-8 weeks post-surgery
• Preoperative contrast study to rule out distal stricture

7.4 Refeeding Protocol (Post-NEC)

Prerequisites for Refeeding:

• Resolved abdominal distension
• Passing stool/flatus
• Normal abdominal examination
• Stable inflammatory markers
• Minimum NPO duration completed

Refeeding Protocol:

Signs of Intolerance (Hold/Reduce Feeds):

• Gastric residuals > 30% of previous feed
• Bilious aspirates (new)
• Abdominal distension (increase in girth)
• Bloody stools
• Vomiting
• Apnoea/bradycardia episodes

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8. Complications

Acute Complications

Long-Term Complications

Short Bowel Syndrome (SBS)

Definition: Malabsorption due to less than 75 cm (or less than 35-50% expected) small bowel remaining [11]

Surgical Options for SBS:

• STEP Procedure (Serial Transverse Enteroplasty): Lengthens and tapers dilated bowel
• Bianchi Procedure: Longitudinal intestinal lengthening
• Intestinal Transplant: Last resort; 50-70% 5-year survival

Intestinal Stricture

Incidence: 15-35% of NEC survivors [11]

Characteristics:

• Typically develops 3-8 weeks after NEC episode
• Most common site: Colon (especially left colon)
• Result of scar tissue formation during healing

Presentation:

• Feeding intolerance
• Abdominal distension
• Failure to thrive
• Vomiting
• Constipation/obstipation

Diagnosis:

• Contrast enema (water-soluble contrast)
• May be asymptomatic (routine screening before stoma reversal)

Management:

• Surgical resection with primary anastomosis
• Balloon dilatation (selected cases)
• Strictureplasty (rarely)

Neurodevelopmental Impairment

Prevalence: 25-45% of NEC survivors show some impairment [15]

Follow-up Requirements:

• Bayley Scales at 18-24 months corrected age
• School readiness assessment at 4-5 years
• Ongoing developmental surveillance
• Nutritional monitoring

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9. Prevention

Evidence-Based Prevention Strategies

Human Milk and Donor Milk

Protective Components of Human Milk:

Donor Human Milk:

• Pasteurised donor human milk (DHM) preferred over formula if mother's own milk unavailable
• Retains protective effects though some immunological components reduced
• Cost-effectiveness demonstrated in VLBW infants [16]

Probiotics

Efficacy: Cochrane meta-analysis demonstrates ~50% reduction in NEC (RR 0.46, 95% CI 0.36-0.59) [25]

Strain Selection:

• Lactobacillus rhamnosus GG: Most studied, well-established safety
• Bifidobacterium infantis/longum: Specifically adapted to digest HMOs
• Lactobacillus reuteri: Alternative with good evidence
• Multi-strain combinations: May have additive effects

Administration Protocol:

• Start with first enteral feed
• Continue until 34-36 weeks postmenstrual age
• Typical dose: 10⁸-10⁹ CFU per day

Safety Considerations:

• Rare cases of probiotic sepsis reported
• Use pharmaceutical-grade preparations
• Avoid in critically ill/immunocompromised

Standardised Feeding Protocols

Key Elements:

• Defined initiation criteria (haemodynamic stability)
• Standard advancement rates (15-30 mL/kg/day)
• Clear definitions of feeding intolerance
• Consistent nursing and physician education

Evidence:

• Reduction in NEC rates by 40-60% in before-after studies
• Reduced variation in practice
• Protocol compliance more important than specific advancement rate [21]

Antibiotic Stewardship

Risk Mitigation:

• Limit empiric antibiotics to 48-72 hours if cultures negative
• Avoid H2 blockers/PPIs when possible
• Early transition to enteral feeds
• Culture-directed therapy when positive

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10. Prognosis and Outcomes

Mortality

Predictors of Poor Outcome

Clinical:

• Birth weight less than 750g
• Gestational age less than 26 weeks
• Inotrope requirement
• Pneumoperitoneum
• Pan-intestinal involvement

Laboratory:

• pH less than 7.15
• Lactate > 6 mmol/L persistently
• Platelet count less than 30 × 10⁹/L
• DIC

Long-Term Outcomes Summary

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11. Differential Diagnosis

• no pneumatosis, minimal inflammation | | Neonatal Sepsis (with Ileus) | No pneumatosis, no localised findings, generalised hypotonia | AXR shows ileus but no pneumatosis or portal gas | | Midgut Volvulus | Sudden catastrophic deterioration, bilious vomiting, "double bubble" sign | Whirlpool sign on USS, upper GI contrast shows "bird's beak" | | Hirschsprung's Disease | Delayed meconium passage, chronic distension, enterocolitis episodes | Explosive decompression on rectal examination, biopsy confirms | | Milk Protein Allergy | Bloody stools in well-appearing infant, eosinophilia | No systemic toxicity, responds to formula change | | Intussusception | Rare in neonates, "target sign" on USS | Reducible with air/contrast enema | | Meconium Ileus | No feeds given, ground-glass appearance on AXR, CF association | Sweat test, no pneumatosis |

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12. Viva Points and Exam Preparation

Opening Statement

"Necrotising enterocolitis is the most common and serious gastrointestinal emergency in neonates, characterised by intestinal inflammation progressing to ischaemic necrosis. It primarily affects premature infants and results from a complex interplay of intestinal immaturity, abnormal bacterial colonisation, and inflammatory dysregulation following enteral feeding. The Modified Bell's Staging System classifies NEC from suspected (Stage I) through definite (Stage II) to advanced disease with perforation (Stage III), guiding both diagnosis and management."

Key Facts to Quote

• Incidence: 5-12% in VLBW infants (less than 1500g), 10-15% in ELBW (less than 1000g) [7]
• Mortality: 20-30% overall, 40-50% if surgery required [6]
• Human milk reduces risk by 6-10x compared to formula [16]
• Probiotics reduce NEC by ~50% (RR 0.46) [25]
• Thrombocytopenia less than 100 × 10⁹/L highly predictive of surgical disease [13]
• Portal venous gas associated with 33-50% mortality [12]

Common Viva Questions

Q: Describe your approach to a premature infant with abdominal distension and bloody stools.

A: "I would approach this systematically as possible NEC until proven otherwise. Immediately, I would cease enteral feeds, insert a nasogastric tube for decompression, obtain IV access and blood samples including cultures, FBC, coagulation, and blood gas. I would request an urgent abdominal radiograph looking for pneumatosis, portal venous gas, and free air. I would commence broad-spectrum antibiotics covering gram-positives, gram-negatives, and anaerobes. Surgical colleagues would be informed early. Further management would be guided by the Bell's staging based on clinical and radiological findings."

Q: What are the indications for surgery in NEC?

A: "Absolute indications are pneumoperitoneum (free air) and a positive paracentesis showing brown fluid or bacteria. Relative indications include clinical deterioration despite maximal medical therapy, a fixed bowel loop on serial radiographs persisting for more than 24-36 hours, abdominal wall erythema or discolouration, a palpable mass, and persistent severe acidosis with rising lactate levels unresponsive to resuscitation."

Q: What is the pathophysiology of NEC?

A: "NEC develops from the interaction of three essential factors in the vulnerable preterm intestine. First, intestinal immaturity characterised by weak tight junctions, reduced secretory IgA and defensins, and importantly, upregulation of TLR4 receptors that trigger excessive inflammation in response to bacterial endotoxin. Second, abnormal bacterial colonisation or dysbiosis, with dominance of Proteobacteria such as Klebsiella and E. coli rather than protective Bifidobacteria. Third, enteral feeding provides substrate for bacterial fermentation. TLR4 activation triggers NF-κB and release of TNF-alpha and IL-1beta, leading to epithelial apoptosis, vasoconstriction, and mucosal breakdown with bacterial translocation."

Common Mistakes (What Fails Candidates)

• Not recognising subtle early signs (apnoea, feeding intolerance)
• Failing to stage NEC correctly using Bell's criteria
• Not mentioning the role of breast milk in prevention
• Forgetting metronidazole in antibiotic regimen (anaerobic coverage)
• Not knowing absolute vs relative indications for surgery
• Unable to describe the radiological signs (pneumatosis, portal venous gas)
• Not mentioning long-term complications (stricture, SBS, NDI)

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13. References

1. Neu J, Walker WA. Necrotizing enterocolitis. N Engl J Med. 2011;364(3):255-264. doi:10.1056/NEJMra1005408

2. Patel RM, Denning PW. Therapeutic use of prebiotics, probiotics, and postbiotics to prevent necrotizing enterocolitis: what is the current evidence? Clin Perinatol. 2013;40(1):11-25. doi:10.1016/j.clp.2012.12.002

3. Niño DF, Sodhi CP, Hackam DJ. Necrotizing enterocolitis: new insights into pathogenesis and mechanisms. Nat Rev Gastroenterol Hepatol. 2016;13(10):590-600. doi:10.1038/nrgastro.2016.119

4. Hackam DJ, Sodhi CP. Toll-Like Receptor-Mediated Intestinal Inflammatory Imbalance in the Pathogenesis of Necrotizing Enterocolitis. Cell Mol Gastroenterol Hepatol. 2018;6(2):229-238.e2. doi:10.1016/j.jcmgh.2018.04.001

5. Sodhi CP, Neal MD, Siggers R, et al. Intestinal epithelial Toll-like receptor 4 regulates goblet cell development and is required for necrotizing enterocolitis in mice. Gastroenterology. 2012;143(3):708-718.e5. doi:10.1053/j.gastro.2012.05.053

6. Stoll BJ, Hansen NI, Bell EF, et al. Trends in Care Practices, Morbidity, and Mortality of Extremely Preterm Neonates, 1993-2012. JAMA. 2015;314(10):1039-1051. doi:10.1001/jama.2015.10244

7. Holman RC, Stoll BJ, Curns AT, Yorita KL, Steiner CA, Schonberger LB. Necrotising enterocolitis hospitalisations among neonates in the United States. Paediatr Perinat Epidemiol. 2006;20(6):498-506. doi:10.1111/j.1365-3016.2006.00756.x

8. McElhinney DB, Hedrick HL, Bush DM, et al. Necrotizing enterocolitis in neonates with congenital heart disease: risk factors and outcomes. Pediatrics. 2000;106(5):1080-1087. doi:10.1542/peds.106.5.1080

9. Gephart SM, McGrath JM, Effken JA, Halpern MD. Necrotizing enterocolitis risk: state of the science. Adv Neonatal Care. 2012;12(2):77-87. doi:10.1097/ANC.0b013e31824cee94

10. Rees CM, Eaton S, Kiely EM, Wade AM, McHugh K, Pierro A. Peritoneal drainage or laparotomy for neonatal bowel perforation? A randomized controlled trial. Ann Surg. 2008;248(1):44-51. doi:10.1097/SLA.0b013e318176bf81

11. Elfvin A, Dinsdale E, Wales PW, Moore AM. Long-term outcomes following necrotizing enterocolitis and surgical management: a systematic review and meta-analysis. J Pediatr Surg. 2018;53(5):976-983. doi:10.1016/j.jpedsurg.2018.02.018

12. Epelman M, Daneman A, Navarro OM, et al. Necrotizing enterocolitis: review of state-of-the-art imaging findings with pathologic correlation. Radiographics. 2007;27(2):285-305. doi:10.1148/rg.272055098

13. Patel RM, Knezevic A, Shenvi N, et al. Association of Red Blood Cell Transfusion, Anemia, and Necrotizing Enterocolitis in Very Low-Birth-Weight Infants. JAMA. 2016;315(9):889-897. doi:10.1001/jama.2016.1204

14. Ballance WA, Dahms BB, Shenker N, Kliegman RM. Pathology of neonatal necrotizing enterocolitis: a ten-year experience. J Pediatr. 1990;117(1 Pt 2):S6-S13. doi:10.1016/s0022-3476(05)81093-8

15. Rees CM, Pierro A, Eaton S. Neurodevelopmental outcomes of neonates with medically and surgically treated necrotizing enterocolitis. Arch Dis Child Fetal Neonatal Ed. 2007;92(3):F193-F198. doi:10.1136/adc.2006.099929

16. Lucas A, Cole TJ. Breast milk and neonatal necrotising enterocolitis. Lancet. 1990;336(8730):1519-1523. doi:10.1016/0140-6736(90)93304-8

17. Havranek T, Johanboeke P, Madramootoo C, Carver JD. Umbilical artery catheters do not affect intestinal blood flow responses to minimal enteral feedings. J Perinatol. 2007;27(6):375-379. doi:10.1038/sj.jp.7211704

18. Cotten CM, Taylor S, Stoll B, et al. Prolonged duration of initial empirical antibiotic treatment is associated with increased rates of necrotizing enterocolitis and death for extremely low birth weight infants. Pediatrics. 2009;123(1):58-66. doi:10.1542/peds.2007-3423

19. Guillet R, Stoll BJ, Cotten CM, et al. Association of H2-blocker therapy and higher incidence of necrotizing enterocolitis in very low birth weight infants. Pediatrics. 2006;117(2):e137-e142. doi:10.1542/peds.2005-1543

20. Mohamed A, Shah PS. Transfusion associated necrotizing enterocolitis: a meta-analysis of observational data. Pediatrics. 2012;129(3):529-540. doi:10.1542/peds.2011-2872

21. Morgan J, Bombell S, McGuire W. Early trophic feeding versus enteral fasting for very preterm or very low birth weight infants. Cochrane Database Syst Rev. 2013;(3):CD000504. doi:10.1002/14651858.CD000504.pub4

22. Pammi M, Cope J, Tarr PI, et al. Intestinal dysbiosis in preterm infants preceding necrotizing enterocolitis: a systematic review and meta-analysis. Microbiome. 2017;5(1):31. doi:10.1186/s40168-017-0248-8

23. Bell MJ, Ternberg JL, Feigin RD, et al. Neonatal necrotizing enterocolitis. Therapeutic decisions based upon clinical staging. Ann Surg. 1978;187(1):1-7. doi:10.1097/00000658-197801000-00001

24. Moss RL, Dimmitt RA, Barnhart DC, et al. Laparotomy versus peritoneal drainage for necrotizing enterocolitis and perforation. N Engl J Med. 2006;354(21):2225-2234. doi:10.1056/NEJMoa054605

25. AlFaleh K, Anabrees J. Probiotics for prevention of necrotizing enterocolitis in preterm infants. Cochrane Database Syst Rev. 2014;(4):CD005496. doi:10.1002/14651858.CD005496.pub4

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14. Appendices

Appendix A: Nursing Care Bundle for NEC

Appendix B: Discharge Checklist

• Stoma care education complete (if applicable)
• Parents confident with stoma bag changes
• Stoma supplies ordered for home
• Tolerating full enteral feeds
• Growth trajectory documented
• LFTs normal (if prolonged TPN)
• Fat-soluble vitamins/B12 supplementation (if SBS)
• Surgical follow-up appointment booked
• Contrast study for stricture screening (if stoma present)
• Developmental follow-up arranged
• Dietitian referral (if SBS)

Appendix C: Long-Term Surveillance Schedule

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