What are the treatment options for an infant presenting with projectile vomiting?

Treatment of Projectile Vomiting in Infants

The treatment approach for an infant with projectile vomiting depends critically on whether the vomiting is bilious or non-bilious, with bilious vomiting requiring immediate surgical evaluation for malrotation with volvulus, while non-bilious projectile vomiting most commonly indicates hypertrophic pyloric stenosis (HPS) requiring surgical pyloromyotomy after fluid resuscitation. 1, 2

Immediate Triage and Assessment

Determine if vomiting is bilious (green) or non-bilious first—this single distinction changes everything: 1, 2

• Bilious vomiting = surgical emergency until proven otherwise, requiring immediate imaging (abdominal X-ray looking for obstruction patterns) and surgical consultation for possible malrotation with volvulus 2
• Non-bilious projectile vomiting in a 2-8 week old infant = suspect HPS as the most common surgical cause 1

Assess hydration status immediately using specific markers: 1

• Mild dehydration: 3-5% deficit
• Moderate dehydration: 6-9% deficit
• Severe dehydration: ≥10% deficit (prolonged skin tenting, cool extremities, decreased capillary refill) 1, 2

Diagnostic Workup for Non-Bilious Projectile Vomiting

Physical examination must include palpation for the pathognomonic "olive" mass in the right upper quadrant, which confirms HPS. 1

Ultrasound is the imaging modality of choice for suspected HPS in infants older than 2 weeks with new onset non-bilious projectile vomiting. 1

Common pitfall: While HPS typically presents between 3-6 weeks of age, it can occur later—one case series documented HPS in an 8-month-old, so maintain suspicion in older infants with appropriate symptoms. 2, 3

Treatment Algorithm

For Confirmed or Suspected HPS (Surgical Cause):

1. Withhold feeds immediately and place nasogastric tube for gastric decompression 1

2. Initiate IV fluid resuscitation to correct dehydration and metabolic abnormalities before surgery: 1

• Administer IV fluids to correct the typical hypochloremic, hypokalemic metabolic alkalosis
• Preoperative preparation is essential to optimal surgical outcome 4

3. Obtain immediate surgical consultation for pyloromyotomy 1

• Pyloromyotomy is the definitive treatment for HPS
• Gastric emptying returns to normal 8-16 days post-operatively 5

For Non-Obstructive Causes (GERD/Viral Gastroenteritis):

If the infant has normal weight gain, passes gas and stool regularly, and has no palpable olive mass, mechanical obstruction is unlikely and medical management is appropriate: 1

1. Oral rehydration is the cornerstone of treatment: 1, 2

• Administer oral rehydration solution (ORS) in small, frequent volumes (5 mL every minute initially) using a spoon or syringe 1
• Replace each vomiting episode with 10 mL/kg of ORS 1
• For severe dehydration or inability to tolerate oral intake, use IV rehydration 2

2. Continue appropriate feeding: 1

• Continue breastfeeding on demand—breast milk should never be interrupted 1
• For formula-fed infants, continue full-strength formula immediately in amounts sufficient to satisfy energy requirements 1
• Consider smaller, more frequent feeds for GERD 1
• Feed thickening agents may be helpful for GERD 1

3. Ondansetron use is restricted and NOT routine: 1, 6

• Dose: 0.2 mg/kg oral (maximum 4 mg) or 0.15 mg/kg parenteral 1, 6
• Only consider if persistent vomiting prevents oral intake entirely—it should not replace proper fluid and electrolyte management 1, 2
• Generally NOT indicated for routine viral gastroenteritis in young infants 1

4. Avoid antidiarrheal or antimotility agents entirely—these cause serious side effects, are ineffective, and shift focus away from appropriate fluid therapy. 1, 2

Critical Red Flags Requiring Immediate Escalation

Return immediately or escalate care if: 1, 2

• Vomiting becomes bilious (green) 1, 2
• Bloody vomitus or "currant jelly" stools appear (suggests intussusception) 2
• Decreased urine output (fewer than 4 wet diapers in 24 hours) 1
• Poor weight gain on serial measurements (elevates concern from benign reflux to GERD disease requiring aggressive intervention) 1
• Signs of severe dehydration develop 2

Key Clinical Pitfall

Never dismiss bilious vomiting as "just gastroenteritis"—malrotation with volvulus can present at any age, not just in newborns, and accounts for 20% of bilious vomiting cases in the first 72 hours of life. 1, 2