What is the likely cause and appropriate management for a 13‑month‑old infant presenting with multiple episodes of projectile, non‑bilious vomiting of curdled milk, now tolerating small amounts of oral fluids?

Likely Diagnosis and Management of 13-Month-Old with Projectile Vomiting of Curdled Milk

This 13-month-old most likely has food protein-induced enterocolitis syndrome (FPIES) to cow's milk, and you should immediately eliminate all cow's milk from the diet and switch to an extensively hydrolyzed or amino acid-based formula while ensuring adequate hydration. 1

Immediate Assessment

First, confirm the vomiting is non-bilious (curdled milk indicates gastric contents, not bile). The projectile nature with multiple episodes in a 13-month-old who is now tolerating some oral intake suggests an acute FPIES reaction rather than a surgical emergency. 1, 2

Critical Red Flags to Rule Out

• Bilious (green) vomiting would indicate intestinal obstruction and require immediate surgical consultation – this is NOT present based on the description of "curdled milk" vomitus. 3, 2
• Check for signs of severe dehydration: capillary refill >2 seconds, <4 wet diapers in 24 hours, sunken fontanelle, lethargy. 4, 2
• Assess for signs of shock: severe lethargy, hypotonia, ashen appearance, hypotension – these would require immediate IV resuscitation. 1

Why FPIES is the Leading Diagnosis

FPIES to cow's milk typically presents with repetitive projectile vomiting 1-4 hours after ingestion, often with pallor and lethargy, and is classified as "late-onset" when occurring after 9 months of age. 1 Key features that fit:

• Age 13 months falls into the "late-onset" FPIES category (>9 months). 1
• Projectile vomiting of curdled milk indicates gastric contents expelled forcefully after cow's milk ingestion. 1
• Multiple episodes followed by tolerance of some oral fluids is consistent with acute FPIES – symptoms typically resolve within 24 hours after eliminating the trigger food. 1
• Cow's milk is one of the three most common FPIES triggers (along with soy and rice). 1

Severity Classification and Immediate Management

Based on the presentation, classify severity:

If Mild-to-Moderate (1-3 episodes, minimal lethargy, tolerating some PO):

• Continue oral rehydration with small, frequent volumes (5 mL every minute initially using breast milk, clear fluids, or oral rehydration solution). 4, 2
• Monitor at home if the child is alert, has adequate urine output, and can tolerate oral fluids. 1
• Parents should return immediately if vomiting recurs, becomes bilious, or if signs of dehydration develop. 4

If Severe (>4 episodes, severe lethargy, unable to tolerate PO):

• Administer ondansetron 0.15 mg/kg intramuscularly (maximum 16 mg) if age ≥6 months. 1
• Place IV line and give normal saline bolus 20 mL/kg rapidly; repeat as needed. 1
• Consider IV methylprednisolone 1 mg/kg (maximum 60-80 mg) for severe cases. 1
• Transfer to emergency department if persistent hypotension, shock, or extreme lethargy develops. 1

Definitive Dietary Management

Immediately eliminate all cow's milk and cow's milk-containing products from the diet. 1

Formula Selection:

• First-line: Switch to extensively hydrolyzed casein-based formula. 1
• If symptoms persist after 3-10 days, switch to amino acid-based formula (10-20% of FPIES patients require this). 1
• Do NOT use soy formula without physician supervision – 20-40% of US patients with cow's milk FPIES also react to soy. 1
• Avoid goat and sheep milk – high protein homology makes cross-reactivity likely. 1

If Breastfed:

• Continue breastfeeding – maternal dietary elimination of cow's milk is NOT routinely recommended. 1
• Breastfeeding should be maintained whenever possible. 1

Expected Clinical Course

Infants with chronic FPIES typically return to baseline within 3-10 days of switching to hypoallergenic formula. 1 Monitor for:

• Resolution of vomiting within 24 hours of trigger elimination. 1
• Weight gain improvement over the next 1-2 weeks. 1
• Normal growth trajectory restoration. 1

Important Caveats

Do NOT confuse this with pyloric stenosis – that presents at 2-12 weeks of age (not 13 months) with a palpable epigastric "olive" mass and metabolic alkalosis. 2

Do NOT confuse this with simple gastroesophageal reflux – GERD causes daily regurgitation in 40-50% of healthy infants but does not typically cause acute episodes of severe projectile vomiting. 2, 5

If vomiting becomes bilious at any point, this changes everything – immediate surgical evaluation for malrotation/volvulus is required regardless of age. 3, 2

Follow-Up and Future Food Challenges

• Avoid the trigger food completely until formal evaluation by pediatric allergist. 1
• Future oral food challenges should be performed in a monitored medical setting with IV access available, given the history of severe symptoms. 1
• Most children with cow's milk FPIES develop tolerance by age 3-5 years, but this requires supervised challenge testing to confirm. 1