Necrotizing Enterocolitis
Neonatology / Pediatric Surgery
Illness script · Neonatology / Pediatric Surgery
Necrotizing Enterocolitis
Acute transmural intestinal necrosis in premature neonates, driven by ischemia, bacterial invasion, and uncontrolled inflammation of the immature gut.
This illness script for Necrotizing Enterocolitis covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Prematurity (<32 weeks GA) is the single greatest risk factor
- VLBW (<1500 g) — risk inversely proportional to gestational age
- Formula feeding (breast milk is strongly protective)
- Perinatal asphyxia or hemodynamic instability reducing mesenteric flow
- Polycythemia, congenital heart disease (especially left-sided lesions)
- Umbilical artery catheterization, hyperosmolar feeds
02
Presentation
- Typical onset: 2–3 weeks of life (later in more premature infants)
- Classic triad: abdominal distension, bloody stools, feeding intolerance
- Bilious gastric residuals/emesis; absent bowel sounds
- Systemic signs: temperature instability, apnea, lethargy, hemodynamic shock
- Blue-gray abdominal wall discoloration = peritonitis/perforation (late, ominous sign)
03
Pathophysiology
- Immature gut: reduced IgA, mucus, and motility → defective mucosal barrier
- Intestinal ischemia → epithelial breakdown → bacterial translocation
- Gas-forming bacteria invade bowel wall → pneumatosis intestinalis
- Systemic endotoxin release triggers sepsis cascade; can progress to perforation
04
Diagnostics
- Abdominal X-ray is first-line: pneumatosis intestinalis is pathognomonic (gas in bowel wall)
- Portal venous gas on AXR = severe disease; pneumoperitoneum = perforation/surgical emergency
- Serial AXRs every 6–8 h in unstable patients to track progression
- Labs: thrombocytopenia, neutropenia, metabolic acidosis, elevated CRP, blood cultures
- Bell's staging (I–III) guides management; stage IIb+ = high surgical risk
05
Management
- Medical (Bell I–IIa): NPO, NG decompression, IV fluids, TPN
- Broad-spectrum antibiotics: ampicillin + gentamicin ± metronidazole for 7–14 days
- Surgical indications: pneumoperitoneum, clinical deterioration despite medical therapy, portal venous gas
- Surgery: peritoneal drain (bridge in unstable VLBW) or exploratory laparotomy with bowel resection
- Prevention: exclusive breast milk feeding; probiotics show promise but not yet standard of care
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Spontaneous Intestinal Perforation
SIP causes isolated ileocecal perforation in VLBW infants without diffuse pneumatosis intestinalis, often linked to indomethacin or postnatal steroid use.
Hirschsprung-Associated Enterocolitis
HAEC typically affects term/near-term infants with prior history of delayed meconium passage and chronic constipation, lacking pneumatosis on AXR.
Malrotation with Midgut Volvulus
Volvulus presents with sudden bilious emesis in a term neonate; AXR shows paucity of gas or 'bird-beak' on UGI series, not pneumatosis.
Neonatal Sepsis
Sepsis lacks the focal abdominal findings; pneumatosis intestinalis on X-ray firmly localizes pathology to the bowel wall in NEC.
Keep reading
Full library- Myocardial InfarctionIrreversible myocardial ischemia causing cardiomyocyte necrosis, most often from acute coronary artery occlusion by thrombus on ruptured atherosclerotic plaque.
- Necrotizing FasciitisRapidly spreading bacterial infection of the deep fascia causing tissue necrosis, systemic toxicity, and high mortality if not surgically debrided emergently.
Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.