What causes bilious vomiting?

Causes of Bilious Vomiting

Bilious vomiting is a critical sign of intestinal obstruction until proven otherwise and requires immediate medical attention, particularly in neonates where it may indicate life-threatening conditions requiring urgent surgical intervention. 1, 2

Anatomical Causes of Bilious Vomiting

In Neonates (0-28 days)

• Congenital malformations (most common in first days of life):
  • Malrotation with or without midgut volvulus (20% of cases with bilious vomiting in first 72 hours) 1
  • Intestinal atresia (duodenal, jejunal, ileal) 1, 3
  • Annular pancreas 1
  • Hirschsprung disease 1
  • Meconium ileus 3

In Infants and Children

• Acquired obstructions:
  • Intussusception (uncommon in first 3 months) 1
  • Adhesive bands 4
  • Jejunal strictures due to non-specific jejunoileitis 4
  • Incarcerated hernia 3
  • Foreign body obstruction 1
  • Gastric volvulus 1

Non-Anatomical Causes

Functional Obstructions

• Functional immaturity of the colon 1
• Meconium plug syndrome 1
• Paralytic ileus (often secondary to sepsis or electrolyte abnormalities)

Inflammatory Conditions

• Necrotizing enterocolitis (particularly in premature infants) 3
• Neonatal appendicitis 1
• Enteritis 1

Systemic Conditions

• Sepsis 1
• Meningitis 1
• Raised intracranial pressure (tumor, trauma, hydrocephalus) 1
• Metabolic disorders (phenylketonuria, hyperammonemia, maple syrup urine disease, galactosemia, adrenocortical hyperplasia) 1

Clinical Significance by Age Group

Neonates

Bilious vomiting in neonates is an ominous sign requiring immediate evaluation. In a study of neonates with bilious vomiting, 46% had a surgical diagnosis and 14.1% had a time-critical surgical condition where delay could compromise gut viability 5. The presence of abdominal distension, tenderness, and abnormal abdominal X-ray findings were significantly associated with surgical conditions 5.

Older Infants and Children

In older infants and children, chronic bilious vomiting may be caused by partial obstructions such as jejunal strictures, which were found in 25% of children with bilious vomiting in one study from developing countries 4.

Diagnostic Approach

1. Initial assessment: Place nasogastric tube to decompress the stomach 3
2. Physical examination: Look for abdominal distension, tenderness, palpable masses ("olive" in pyloric stenosis) 1, 6
3. Imaging:
   • Plain abdominal radiographs (first-line) to assess for dilated bowel loops and air-fluid levels 3
   • Ultrasound for specific conditions (e.g., pyloric stenosis, intussusception) 6
   • Upper GI series if malrotation is suspected 1
   • Contrast enema for distal obstructions 1

Important Caveats

• Normal abdominal X-ray reduces the probability of surgical diagnosis but does not exclude it completely 5
• Clinical findings at referral may not reliably differentiate between infants with or without time-critical surgical conditions 5
• Non-bilious vomiting is more commonly associated with non-surgical conditions like gastroesophageal reflux or formula intolerance 1
• Hyperemesis gravidarum can cause vomiting in pregnant women but is typically non-bilious 1

Remember that bilious vomiting represents obstruction distal to the ampulla of Vater and should always be considered a surgical emergency until proven otherwise, particularly in neonates.