✅ NECROTIZING ENTEROCOLITIS (NEC)
1. Definition
Necrotizing Enterocolitis (NEC) is a life-threatening inflammatory bowel disease of neonates, characterized by:
- Intestinal mucosal injury
- Bacterial invasion
- Bowel wall necrosis
- Possible perforation and peritonitis
Most common in preterm, low birth weight infants.
2. Pathophysiology
NEC develops due to a combination of:
Immature gut barrier
- Weak mucosal defense
- Increased intestinal permeability
Dysregulated intestinal microbiome
- Abnormal bacterial colonization
Intestinal ischemia
- Poor mesenteric perfusion
- Hypoxia → mucosal injury
Feeding-related injury
- Formula feeding increases risk
- Breast milk is protective
Inflammatory cascade
- Release of cytokines (TNF-α, IL-6)
- Bowel necrosis → gas in bowel wall (pneumatosis intestinalis)
3. Causes / Risk Factors
Major Risk Factors
- Prematurity (<32 weeks)
- Very low birth weight (<1500 g)
- Formula feeding
- Perinatal asphyxia
- Sepsis
- Patent ductus arteriosus (PDA)
- Umbilical catheterization
Infectious triggers
- Gram-negative bacteria
- Clostridium species
4. Clinical Features
Early Signs
- Feeding intolerance
- Increased gastric residuals
- Abdominal distension
- Vomiting
Gastrointestinal Signs
- Bloody stools
- Abdominal tenderness
- Visible bowel loops
Systemic Signs
- Apnea
- Bradycardia
- Temperature instability
- Lethargy
- Shock (late)
5. Investigations / Diagnosis
Laboratory
- CBC: neutropenia or leukocytosis
- Thrombocytopenia (severe disease)
- Metabolic acidosis
- Elevated CRP
Radiology (Key)
- Abdominal X-ray:
Pathognomonic
- Pneumatosis intestinalis (air in bowel wall)
Severe signs
- Portal venous gas
- Pneumoperitoneum (free air → perforation)
Ultrasound
- Free fluid
- Bowel wall thickening
- Reduced perfusion
6. Differential Diagnosis
- Neonatal sepsis with ileus
- Hirschsprung-associated enterocolitis
- Intestinal obstruction (malrotation, volvulus)
- Milk protein allergy
- Spontaneous intestinal perforation
7. Management (Stepwise)
A. Immediate Stabilization
- Stop feeds (NPO)
- Nasogastric decompression
- IV fluids + electrolytes
- Parenteral nutrition
B. Antibiotic Therapy
Empiric regimen (7–14 days)
1. Ampicillin
- Indication: Gram-positive + Listeria coverage
- MOA: inhibits bacterial cell wall synthesis
- Dose:
* Preterm: 50 mg/kg IV q12h
* Term: 50 mg/kg IV q8h
- Adverse effects: rash, diarrhea
- Contraindication: penicillin allergy
- Monitoring: renal function
2. Gentamicin
- Indication: Gram-negative coverage
- MOA: inhibits 30S ribosome → bactericidal
- Dose: 4–5 mg/kg IV q24–48h
- Adverse effects: nephrotoxicity, ototoxicity
- Monitoring: trough levels, creatinine
- Interactions: other nephrotoxic drugs
3. Metronidazole (or Clindamycin)
- Indication: Anaerobic coverage
- MOA: DNA strand breakage
- Dose: 7.5 mg/kg IV q8–12h
- Adverse effects: neurotoxicity (rare), GI upset
- Monitoring: liver function
C. Supportive Care
- Respiratory support if apnea
- Treat shock with vasopressors
- Correct coagulopathy (FFP/platelets)
D. Surgical Management
Indications:
- Pneumoperitoneum
- Bowel perforation
- Necrotic bowel
- Clinical deterioration despite medical care
Procedures:
- Peritoneal drain (unstable VLBW)
- Laparotomy with bowel resection
- Stoma formation
8. Complications
- Intestinal perforation
- Peritonitis
- Strictures
- Short bowel syndrome
- Neurodevelopmental impairment
- Death
9. Prevention
- Exclusive breast milk feeding
- Probiotics (in some NICUs)
- Slow advancement of feeds
- Avoid unnecessary antibiotics
✅ NEONATAL SEPSIS
1. Definition
Neonatal sepsis is a systemic infection with bacteremia occurring in infants ≤28 days.
2. Classification
Early-Onset Sepsis (EOS)
- <72 hours of life
- Vertical transmission from mother
Late-Onset Sepsis (LOS)
- > 72 hours
- Hospital-acquired or community-acquired
3. Pathophysiology
- Immature immune system
- Reduced neutrophil function
- Poor complement activity
- Rapid bacterial spread → cytokine storm → shock
4. Causes / Organisms
EOS Common Organisms
- Group B Streptococcus
- E. coli
- Listeria monocytogenes
LOS Organisms
- Coagulase-negative Staphylococci
- Staphylococcus aureus
- Klebsiella, Pseudomonas
- Candida (fungal)
5. Risk Factors
Maternal
- Prolonged rupture of membranes >18h
- Chorioamnionitis
- Maternal fever
- GBS colonization
Neonatal
- Prematurity
- Low birth weight
- Central lines
- Mechanical ventilation
6. Clinical Features
Nonspecific Presentation
- Poor feeding
- Lethargy
- Hypothermia or fever
- Irritability
Respiratory
- Apnea
- Tachypnea
- Respiratory distress
Cardiovascular
- Poor perfusion
- Hypotension
- Shock
GI
- Vomiting
- Abdominal distension
- NEC association
CNS
- Seizures
- Bulging fontanelle (meningitis)
7. Investigations / Diagnosis
Gold Standard
- Blood culture
Sepsis Screen
- CBC (low ANC, leukopenia)
- CRP, Procalcitonin
- Immature-to-total neutrophil ratio (I/T >0.2)
Lumbar puncture
- If meningitis suspected
Other cultures
- Urine culture (LOS)
- CSF culture
Imaging
- Chest X-ray if pneumonia suspected
8. Differential Diagnosis
- Hypoglycemia
- Respiratory distress syndrome
- Congenital heart disease
- Inborn errors of metabolism
- NEC
9. Management (Stepwise)
A. Immediate Resuscitation
- Airway + oxygen
- IV access
- Fluids (10 mL/kg bolus cautiously)
- Treat shock early
B. Empiric Antibiotics
Early-Onset Sepsis Regimen
Ampicillin + Gentamicin
(Details already above)
Late-Onset Sepsis Regimen
1. Vancomycin
- Indication: MRSA, CoNS
- MOA: inhibits cell wall synthesis
- Dose: 15 mg/kg IV q12–24h
- Adverse effects: nephrotoxicity, Red man syndrome
- Monitoring: trough levels, renal function
- Contraindication: hypersensitivity
2. Cefotaxime (alternative)
- Indication: Gram-negative meningitis
- MOA: 3rd-gen cephalosporin inhibits cell wall
- Dose: 50 mg/kg IV q8–12h
- Adverse effects: diarrhea, biliary sludge
- Avoid: routine use due to resistance risk
3. Meropenem (severe MDR infection)
- MOA: broad-spectrum carbapenem
- Dose: 20–40 mg/kg IV q8–12h
- Adverse effects: seizures (rare)
- Monitoring: renal function
C. Supportive Care
- Maintain glucose
- Treat metabolic acidosis
- Platelets for DIC
- Inotropes (dopamine/dobutamine)
D. Duration of Treatment
- Culture-negative sepsis: 5–7 days
- Proven bacteremia: 10–14 days
- Meningitis: 21 days or more
10. Complications
- Septic shock
- DIC
- Meningitis → neurodevelopmental delay
- NEC
- Death
11. Prevention
- Maternal GBS screening + intrapartum prophylaxis
- Strict NICU infection control
- Breastfeeding
- Early removal of invasive lines
✅ NEC vs Neonatal Sepsis (Quick Comparison)
| Feature | NEC | Neonatal Sepsis |
| ------------ | ----------------------------------------- | ----------------------------- |
| Primary site | Intestine | Systemic infection |
| Key sign | Pneumatosis intestinalis | Positive blood culture |
| Stool blood | Common | Possible |
| Management | NPO + bowel rest + surgery if perforation | Antibiotics + supportive care |
| Risk | Formula feeding, prematurity | PROM, maternal infection |
