Below is a concise but complete pediatric reference for both conditions.
Necrotizing Enterocolitis (NEC)
Definition
Necrotizing enterocolitis (NEC) is a severe gastrointestinal emergency in neonates characterized by intestinal inflammation, ischemia, and necrosis, which can lead to intestinal perforation, peritonitis, and sepsis.
It mainly affects premature and low-birth-weight infants.
Epidemiology
- Most common in preterm infants (<32 weeks)
- Peak incidence: 2–3 weeks of life
- Incidence increases with lower gestational age
- Mortality: 20–30%
Pathophysiology
NEC results from interaction of:
- Intestinal immaturity
- Abnormal bacterial colonization
- Enteral feeding
- Intestinal ischemia
Mechanism:
- Premature intestine has immature mucosal barrier
- Bacterial colonization leads to inflammation
- Release of cytokines and inflammatory mediators
- Mucosal injury → necrosis
- Gas produced by bacteria accumulates in bowel wall → pneumatosis intestinalis
- May progress to perforation and peritonitis
Risk Factors
Maternal
- Chorioamnionitis
- Placental insufficiency
- Maternal hypertension
- Cocaine use
Neonatal
- Prematurity
- Low birth weight
- Formula feeding
- Hypoxia
- Congenital heart disease
- Sepsis
- Polycythemia
- Exchange transfusion
Clinical Features
Usually appear after feeding begins.
Gastrointestinal
- Feeding intolerance
- Vomiting
- Abdominal distension
- Abdominal tenderness
- Bloody stools
- Gastric residuals
Systemic signs
- Lethargy
- Temperature instability
- Apnea
- Bradycardia
- Hypotension
Severe disease
- Abdominal wall erythema
- Peritonitis
- Shock
Staging (Modified Bell Staging)
Stage I – Suspected
- Feeding intolerance
- Mild abdominal distension
- Gastric residuals
- Mild ileus
Stage II – Definite
- Abdominal distension
- Bloody stools
- Pneumatosis intestinalis on X-ray
Stage III – Advanced
- Severe illness
- Metabolic acidosis
- DIC
- Hypotension
- Bowel perforation
Investigations
Laboratory
- CBC → neutropenia or leukocytosis
- Thrombocytopenia
- Metabolic acidosis
- Electrolyte imbalance
- Elevated CRP
Imaging
Abdominal X-ray findings
Characteristic signs:
- Pneumatosis intestinalis (gas in bowel wall)
- Portal venous gas
- Dilated bowel loops
- Pneumoperitoneum (if perforation)
Differential Diagnosis
- Neonatal sepsis
- Spontaneous intestinal perforation
- Hirschsprung enterocolitis
- Malrotation with volvulus
- Intestinal obstruction
Management
1. Initial Stabilization
- Stop enteral feeds (NPO)
- Nasogastric decompression
- IV fluids
- Electrolyte correction
- Oxygen support
2. Antibiotic Therapy
Common regimen:
Ampicillin
Indication: Gram-positive coverage
Mechanism
Inhibits bacterial cell wall synthesis.
Dose
- Neonate: 50 mg/kg IV every 8–12 h
Adverse effects
- Rash
- Diarrhea
- Hypersensitivity
Gentamicin
Indication: Gram-negative coverage
Mechanism
Inhibits bacterial protein synthesis (30S ribosome).
Dose
- Neonate: 4–5 mg/kg IV once daily
Adverse effects
- Nephrotoxicity
- Ototoxicity
Monitoring
- Drug levels
- Renal function
Metronidazole
Indication: Anaerobic bacteria
Mechanism
DNA damage in anaerobes.
Dose
- Neonate: 7.5 mg/kg IV every 12 h
Adverse effects
- Nausea
- Metallic taste
- Neurotoxicity (rare)
3. Supportive Care
- Total parenteral nutrition (TPN)
- Fluid resuscitation
- Blood transfusion if needed
- Monitor abdominal girth
- Serial X-rays
4. Surgical Management
Indications:
- Intestinal perforation
- Pneumoperitoneum
- Worsening despite medical therapy
Procedures:
- Peritoneal drainage
- Resection of necrotic bowel
- Ileostomy/colostomy
Complications
- Intestinal perforation
- Sepsis
- Short bowel syndrome
- Strictures
- Growth failure
Prevention
- Breastfeeding
- Probiotics (in some NICUs)
- Slow feeding advancement
- Good infection control
Prognosis
- Mortality: 20–30%
- Survivors may develop intestinal strictures or short bowel syndrome
Neonatal Sepsis
Definition
Neonatal sepsis is a systemic infection occurring in infants within the first 28 days of life, confirmed by positive blood culture or strong clinical suspicion with systemic signs.
Classification
Early Onset Sepsis (EOS)
- Occurs within first 72 hours
- Usually vertical transmission from mother
Common organisms:
- Group B Streptococcus
- E. coli
- Listeria monocytogenes
Late Onset Sepsis (LOS)
- Occurs after 72 hours
- Often hospital acquired
Common organisms:
- Staphylococcus aureus
- Coagulase-negative staphylococci
- Klebsiella
- Pseudomonas
- Candida
Risk Factors
Maternal
- Premature rupture of membranes >18 h
- Maternal fever
- Chorioamnionitis
- Group B Streptococcus colonization
Neonatal
- Prematurity
- Low birth weight
- Invasive procedures
- Mechanical ventilation
- Prolonged hospitalization
Pathophysiology
- Pathogens enter bloodstream via
* placenta
* birth canal
* hospital environment
- Immature immune system leads to:
* decreased neutrophil function
* reduced complement activity
- Infection causes systemic inflammatory response
- Leads to:
* septic shock
* multiorgan dysfunction
Clinical Features
Symptoms are often nonspecific.
General
- Poor feeding
- Lethargy
- Irritability
- Temperature instability
Respiratory
- Tachypnea
- Apnea
- Respiratory distress
Cardiovascular
- Hypotension
- Poor perfusion
Gastrointestinal
- Abdominal distension
- Vomiting
Neurological
- Seizures
- Bulging fontanelle
Investigations
Blood tests
- CBC
- CRP
- Procalcitonin
- Blood culture (gold standard)
Other tests
- Lumbar puncture (suspected meningitis)
- Urine culture (late onset)
- Chest X-ray if respiratory symptoms
Management
Initial Support
- Oxygen
- IV fluids
- Temperature control
- Monitor vitals
Antibiotic Therapy
Early Onset Sepsis
Ampicillin + Gentamicin
Covers:
- Group B streptococcus
- Listeria
- Gram negative bacteria
Duration:
- 7–10 days
- 14–21 days if meningitis
Cefotaxime
Used if meningitis suspected.
Mechanism
Inhibits bacterial cell wall synthesis.
Dose
- Neonate: 50 mg/kg IV every 8–12 h
Adverse effects
- Diarrhea
- Allergy
- Resistance risk
Late Onset Sepsis
Common regimen:
Vancomycin
Indication: MRSA and resistant gram positive bacteria
Mechanism
Inhibits cell wall synthesis.
Dose
- 10–15 mg/kg IV every 12 h
Adverse effects
- Nephrotoxicity
- Red man syndrome
Monitoring
- Trough levels
Gentamicin / Cefotaxime
For gram negative coverage.
Complications
- Septic shock
- Disseminated intravascular coagulation (DIC)
- Meningitis
- Pneumonia
- Death
Prevention
- Maternal GBS screening
- Intrapartum antibiotic prophylaxis
- Sterile NICU practices
- Early breastfeeding
Prognosis
- Mortality: 10–30%
- Higher in preterm infants
If you want, I can also provide 30–40 high-yield MCQs on NEC and neonatal sepsis for pediatrics exams (NEET-PG / NEXT / USMLE level).
