When is vomiting considered bilious in cases of suspected intestinal obstruction?

Bilious Vomiting in Suspected Intestinal Obstruction

Vomiting is considered bilious when it contains bile, appearing green or yellow-green in color, which indicates that the obstruction is distal to the ampulla of Vater (beyond the duodenum). This finding is a critical sign that requires urgent evaluation, particularly in neonates and infants, as it often indicates intestinal obstruction that may require immediate surgical intervention 1.

Clinical Significance of Bilious Vomiting

Bilious vomiting is an ominous sign that suggests the possibility of bowel obstruction and in some cases the need for urgent surgery. Key points to understand:

• It indicates that the obstruction is distal to the entry of bile into the duodenum
• In neonates, bilious vomiting in the first 72 hours of life is particularly concerning, with studies showing that 20% had midgut volvulus and 11% had lower GI causes 1
• In adults after bariatric surgery, bilious vomiting suggests obstruction at the jejuno-jejunostomy or a gastro-gastric fistula 1

Diagnostic Approach

Initial Assessment

1. Appearance of vomitus: Green or yellow-green color confirms bilious content
2. Physical examination findings:
   • Abdominal distension (74% sensitivity for surgical diagnosis) 2
   • Abdominal tenderness (62% sensitivity) 2
   • Assessment of abdominal tension (soft vs. tense)

Imaging Studies

1. Plain abdominal radiographs:

   • First-line imaging study
   • 97% sensitivity for surgical diagnosis 2
   • A normal abdominal X-ray reduces probability of surgical diagnosis from 50% to 16% 2
   • Look for:
     • Dilated bowel loops
     • Air-fluid levels
     • Double or triple bubble sign (in neonates)

2. Upper GI series with contrast:

   • Gold standard for evaluating malrotation in infants
   • Identifies abnormal position of the duodenal-jejunal junction 1
   • Essential when midgut volvulus is suspected

3. Abdominal CT with contrast:

   • First-line diagnostic imaging for suspected bile duct injuries or intra-abdominal fluid collections 1
   • May be complemented with CE-MRCP for exact visualization of biliary injuries 1

Common Causes Based on Age Group

In Neonates and Infants

1. Malrotation with midgut volvulus (surgical emergency)
2. Duodenal atresia (classic "double bubble" sign)
3. Jejunoileal atresia
4. Meconium ileus
5. Foreign body obstruction (e.g., water beads) 3

In Adults

1. Post-surgical complications (especially after bariatric surgery)
2. Internal hernia
3. Adhesions
4. Intussusception
5. Bezoars 1

Management Principles

Immediate Actions

1. Place a nasogastric or orogastric tube for gastric decompression 4
2. Fluid resuscitation and correction of electrolyte imbalances
3. Broad-spectrum antibiotics if peritonitis is suspected

Surgical Considerations

1. Timing is critical: In neonates with bilious vomiting, consider as time-critical until proven otherwise 2
2. For malrotation with volvulus: Urgent surgical exploration (within 12-24 hours) 1
3. For intestinal atresia: Surgical correction based on type and location
4. For internal hernia: Assessment of intestinal viability; if ischemia is present, surgical resection is performed 1

Important Caveats and Pitfalls

1. Delay in diagnosis: Bilious vomiting in neonates should always be considered a surgical emergency until proven otherwise
2. Reliance on clinical signs alone: Clinical findings at referral often do not differentiate between infants with or without time-critical surgical conditions 2
3. Missing malrotation: Up to 15% of children with proximal bowel obstruction may present with non-bilious vomiting initially 1
4. Unusual presentations: Conditions like situs inversus totalis can complicate the diagnosis and management of intestinal obstruction 5

Special Considerations

1. Post-bariatric surgery patients: Bilious vomiting suggests obstruction at the jejuno-jejunostomy or a gastro-gastric fistula 1
2. Unusual vascular causes: Rare conditions like portal vein aneurysm can cause intestinal obstruction with bilious vomiting 6
3. Congenital anomalies: Higher index of suspicion needed in patients with known congenital anomalies

Remember that bilious vomiting requires prompt evaluation and often surgical consultation, as delays in treatment for conditions like midgut volvulus can lead to intestinal necrosis and significantly worse outcomes.