1. Necrotizing Enterocolitis
Pathophysiology

2. Background An acquired disease of acute intestinal necrosis
The most common medical/surgical emergency in neonates
Associated with an increase in morbidity and mortality

3. Incidence Estimated 0.3-2.4 cases/1000 live births
2-5% of all NICU admissions
5-10% of VLBW infants; 11% in infants < 750 grams
Approximately 90% of cases are in preterm infants
Occurs in clusters and sporadically
Incidence is increasing as preterm infant survival rate increases

4. Necrotizing Enterocolitis
described as an inflammatory disease of the bowel

5. Risk Factors Single most important risk factor: Prematurity
Decrease in gestational age = increase risk for NEC
Cocaine exposure (2.5x increased risk)
Excluding cocaine exposure, no maternal or neonatal factors other than prematurity are known.

6. Premature Infant Risk Factors
Immature intestinal barrier
Immature digestion and absorption
Decreased intestinal motility
Poor circulatory regulation
Decreased immunologic factors in GI tract (secretory IgA) with exaggerated inflammatory response
Decreased regenerative capabilities
Increased gastric pH

7. Etiology Unclear & multifactorial
Most likely a combination of factors:
Intestinal ischemia
Bacterial colonization of GI tract
Enteral feedings with poor motility and unabsorbed nutrients leads to bacterial proliferation
Advancing feeds > 20-30ml/kg/day
Hyperosmolar formula
Medications (xanthine derivatives, indomethacin, vitamin E)

8. Pathophysiology
Impaired host intestinal defense system + immunological immaturity  colonization of GI tract with NICU flora
Bacteria may migrate through mucosa  inflammatory reaction/cytokine release
Enteric bacteria produces intraluminal gas

9. Pathophysiology
Accumulation of gas in the submucosal layers of the bowel wall  necrosis
Range of pathology:
Mucosal injury  full thickness injury  perforation

11. Normal Bowel Wall

12. NEC Bowel Wall

13. Staging of NEC Clinical presentation varies among infants with NEC
Ranges from slow and insidious to rapid and progressive
Difficult for the clinician to diagnosis
Dr. Martin Bell (1978) proposed original criteria for staging
Subsequently modified as more became known and increasingly lower gestational ages

14. Bell Staging Criteria Stage IA and IB-suspected NEC Systemic signs
Temp. instability, A/B’s, lethargy
Intestinal signs
Mild abdominal distention, residuals, emesis
Bright red blood from rectum (Stage B)
Radiological signs
Normal or dilated, mild Ileus

15. Bell Staging Criteria Stage IIA-Definite NEC, mildly ill
Systemic signs
Temp. instability, A/B’s, lethargy
Intestinal signs
Same as IB, and decreased or absent BS with or without abdominal tenderness
Radiological signs
Intestinal dilation, Ileus, pneumotosis intestinalis

16. Bell Staging Criteria Stage IIB-Definite NEC, moderately ill
Systemic signs
Temp. instability, A/B’s, lethargy, mild acidosis, and mild thrombocytopenia
Intestinal signs
Same as IIA, and definite abdominal tenderness with or without abdominal cellulitis or RLQ mass, absent BS
Radiological signs
Same as IIA with or without portal vein gas, with or without ascites

17. Bell Staging Criteria
Stage IIIA-Advanced NEC, severely ill, bowel intact
Systemic signs
Same as IIB, and hypotension, bradycardia, severe apnea, respiratory and metabolic acidosis, DIC, neutropenia, and anuria
Intestinal signs
Same as IIB, and signs of generalized peritonitis, marked tenderness, abdominal distension, abdominal wall erythema
Radiological signs
Same as IIB with definite ascites

18. Bell Staging Criteria
Stage IIIB-Advanced NEC, severely ill, bowel perforation
Systemic signs
Same as IIIA
Intestinal signs
Radiological signs
Same as IIB, and pneumoperitoneum

19. Bell Staging is Exhausting!

20. There’s more!
Necessary to differentiate NEC from acquired neonatal intestinal diseases (ANIDs)
Gordon et al propose reclassification for the <1250 gram infant to have 3 sub groups:
Feeding intolerance of prematurity
Medical ANIDs, preterm NEC or viral enteritis (VEI)
Surgical ANIDs: spontaneous perforation (SIP), preterm NEC and VEI

21. Question: is it NEC or feeding intolerance?
Symptoms are similar although not as severe:
Abdominal distention, increase in residual (25 to 50% of feeding volume), emesis
Bile stained emesis/residual – NEC??
Bloody stool??