Neonatal Necrotising Enterocolitis (NEC): Pathogenesis and clinical findings Necrotising Enterocolitis (NEC) Infant Risk Factor:
Extreme Prematurity1 (<28 weeks most commonly) Authors: Rachel Bethune Reviewers: Nicola Adderley Kamran Yusuf* * MD at time of publication Bacterial Colonization Gram Negative bacteria2 colonize gut Infections (sepsis) Immature immune system and gut barriers (tight junctions) Bacteria infiltrate gut lining ↑TLR4 in premature neonates TLR4 binds antigens on gram negative bacteria in gut mucosa Immature circulatory regulation (↑ SVR) Bacteria activate mesentery endothelium TLR4 Formula Feeding Missing breast milk’s protective immune cells and enzymes Insufficient protective mucus layer in gut wall Focal gut necrosis Sepsis Unstable temperature (+) Blood cultures Altered vitals: ↑ (early), ↓ (late): heart rate, respiratory rate (apnea), blood pressure Hypoxia / Ischemic event3 Immature gut: ↓motility, ↓digestion, ↓ goblet cells Impaired mesenteric gut perfusion ↑ release proinflammatory cytokines, ↑ lymphocyte activity, ↑macrophage inflammatory signaling Loss of enteric stem cells Abbreviations • TLR4: Toll-Like Receptor 4; aids fetal gut epithelium differentiation • SVR: systemic vascular resistance Notes 1. Very low birth weight correlates with ↑ severity; may occur in all neonates including term infants 2. ↑ Clostridiaceae and Enterobacteriaceae colonize premature gut = abnormal gut microbiota 3. Infants with cyanotic congenital heart disease or suffer from hypoxic events are at ↑ risk for NEC ↑ enterocyte apoptosis ↑ invasion of gas producing bacteria into bowel wall and portal venous system Impaired gut mucosal healing Ischemic necrosis of intestinal mucosa and gas leaking into tissues Accumulation of gas from bacterial metabolism Complications: Intestinal and/or gut strictures Intestinal perforation, Short gut syndrome, Neurodevelopmental impairment, ↑ neonatal mortality Thrombocytopenia, hyponatremia Abdominal X-Ray: Pneumatosis intestinalis Portal venous gas Dilated, gas-filled bowel loops Pneumoperitoneum Abdominal Distention Bilious Vomiting Bloody Stool Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published May 6, 2019 on