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 www.thecalgaryguide.com