What are the causes of lower gastrointestinal (GI) bleeding in newborns?

Causes of Lower GI Bleeding in Newborns

The most common causes of lower gastrointestinal bleeding in newborns include necrotizing enterocolitis, anal fissures, allergic colitis, and infectious colitis, with necrotizing enterocolitis being the most serious and potentially life-threatening condition requiring immediate intervention. 1, 2

Primary Causes by Category

Serious/Life-Threatening Causes

• Necrotizing Enterocolitis (NEC)

  • Most common GI emergency in newborns, particularly premature infants
  • Typically presents in the first 2 weeks of life
  • Early signs: abdominal distention, lethargy, feeding intolerance
  • May progress to GI bleeding and hemodynamic instability
  • Radiographic hallmark: pneumatosis intestinalis (air in bowel wall)
  • Mortality rate: 20-40% 2

• Malrotation with Volvulus

  • Congenital GI tract abnormality that can present in newborns
  • Can cause severe bleeding with intestinal ischemia
  • Surgical emergency requiring immediate intervention 3, 4

• Hirschsprung Disease

  • Functional obstruction that can lead to enterocolitis and bleeding
  • May present with delayed passage of meconium 3, 4

Common Benign Causes

• Anal Fissures

  • Most common cause of visible rectal bleeding in otherwise healthy infants
  • Small tear in anal mucosa causing bright red blood on stool surface 1

• Allergic Colitis (Milk/Soy Protein Allergy)

  • Common in formula-fed infants or breastfed infants whose mothers consume dairy
  • Presents with blood-streaked stools but minimal systemic symptoms 1

• Infectious Colitis

  • Various bacterial pathogens (Salmonella, Shigella, E. coli)
  • Often accompanied by diarrhea, fever, and other systemic symptoms 1

Less Common Causes

• Intestinal Atresia/Stenosis

  • Congenital obstruction that can present with bleeding 3, 4

• Meconium Ileus/Plug Syndrome

  • Obstruction from thick meconium, may be associated with cystic fibrosis
  • Can cause bleeding with intestinal compromise 4

• Vascular Malformations

  • Rare in newborns but can cause significant bleeding
  • Includes hemangiomas and arteriovenous malformations 1, 5

• Very Early Onset Inflammatory Bowel Disease

  • Rare but increasingly recognized in neonatal period
  • Presents with diarrhea, rectal bleeding, and failure to thrive 1

Diagnostic Approach

1. Initial Assessment

   • Evaluate hemodynamic stability
   • Assess amount and character of bleeding
   • Look for associated symptoms (abdominal distention, vomiting, lethargy)

2. Laboratory Studies

   • Complete blood count to assess for anemia and infection
   • Coagulation studies to rule out bleeding disorders
   • Stool studies for infectious causes

3. Imaging

   • Abdominal X-ray to evaluate for obstruction, pneumatosis intestinalis
   • Ultrasound for suspected intussusception or vascular malformations
   • Consider contrast studies for suspected anatomic abnormalities 3, 4

4. Endoscopic Evaluation

   • Colonoscopy may be indicated for persistent bleeding
   • Can provide both diagnostic and therapeutic intervention 5

Clinical Pearls

• The age of presentation is critical in narrowing the differential diagnosis
• Necrotizing enterocolitis is the most concerning cause in premature infants
• Most cases of lower GI bleeding in otherwise healthy term infants are due to benign, self-limiting conditions
• Bilious vomiting with lower GI bleeding should raise immediate concern for malrotation with volvulus
• The presence of abdominal distention with bloody stools in a premature infant strongly suggests necrotizing enterocolitis

Common Pitfalls

• Mistaking upper GI bleeding for lower GI bleeding (upper GI bleeding can present as bright red blood per rectum in newborns due to rapid transit time)
• Delaying surgical consultation for suspected necrotizing enterocolitis or malrotation
• Failing to consider formula protein allergy in an otherwise well-appearing infant with blood-streaked stools
• Overlooking the possibility of maternal blood ingestion (swallowed during delivery or from cracked nipples during breastfeeding) as a cause of apparent GI bleeding

Understanding the various causes of lower GI bleeding in newborns is essential for appropriate triage, timely diagnosis, and effective management to reduce morbidity and mortality.