What is the differential diagnosis (DD) and management (Mx) for a 3-month-old baby who is breastfeeding (BF) normally but vomiting out the contents of breastfeeding, having vomited twice today?

Differential Diagnosis and Management of a 3-Month-Old with Vomiting

Immediate Assessment Priority

In a 3-month-old breastfeeding infant with only 2 episodes of non-bilious vomiting today, who is otherwise feeding normally, the most likely diagnosis is acute viral gastroenteritis or benign gastroesophageal reflux, and management should focus on maintaining hydration while continuing breastfeeding. 1

Critical Red Flags to Assess Immediately

Determine if any of the following are present, as they would change management urgency:

• Bilious (green) vomiting - indicates obstruction distal to ampulla of Vater and requires immediate surgical evaluation 1, 2
• Projectile vomiting - raises concern for pyloric stenosis (though typically presents 2-8 weeks of age) 1
• Blood in vomit or stool - suggests mucosal injury or more serious pathology 3, 1
• Abdominal distension or tenderness - indicates possible obstruction 3, 4
• Fever, lethargy, or altered mental status - suggests systemic infection or neurologic cause 3, 4
• Poor weight gain or weight loss - elevates concern from benign reflux to GERD disease 1
• Signs of dehydration - decreased urine output (<4 wet diapers/24 hours), sunken fontanelle, poor skin turgor 3, 1

Most Likely Differential Diagnoses (Absence of Red Flags)

1. Acute Viral Gastroenteritis

• Most common cause of vomiting in this age group 4
• Usually self-limiting, often accompanied by diarrhea 3
• Vomiting typically peaks early and improves within 24-48 hours 5

2. Gastroesophageal Reflux (GER)

• Common in infants, peaks at 4 months of age 3
• "Happy spitter" - vomiting without other concerning symptoms 3
• Lower rates in breastfed versus formula-fed infants 3

3. Overfeeding

• Can cause vomiting in otherwise healthy infants 3
• Consider if feeding volumes are excessive 3

4. Milk Protein Allergy

• Can mimic GERD presentation 3
• Consider if vomiting is persistent or associated with irritability 3

Management Approach

Immediate Management (First 24 Hours)

Continue breastfeeding on demand - breast milk should never be interrupted in breastfed infants with vomiting 1

Assess and manage hydration:

• For mild dehydration (3-5% deficit): Administer oral rehydration solution (ORS) 60-120 mL for each vomiting episode 3
• Give ORS in small, frequent volumes (5 mL every minute initially) using spoon or syringe 1
• Replace each vomiting episode with approximately 10 mL/kg ORS 1
• Breastfed infants should continue nursing throughout, supplemented with ORS if needed 3, 1

Avoid inappropriate interventions:

• Do NOT use antiemetics routinely in infants this young with presumed viral gastroenteritis 1
• Ondansetron (0.2 mg/kg oral, max 4 mg) may be considered ONLY if persistent vomiting completely prevents oral intake 1
• Do NOT use antidiarrheal or antimotility agents - these can cause serious side effects and are ineffective 1

When to Escalate Care

Return immediately or call if:

• Vomiting becomes projectile or bilious (green) 1
• Decreased urine output (fewer than 4 wet diapers in 24 hours) 1
• Signs of severe dehydration develop (≥10% deficit): sunken eyes, no tears, very dry mouth, lethargy 3
• Vomiting persists beyond 24-48 hours 4
• Infant becomes lethargic or difficult to arouse 3, 4

If Vomiting Persists Beyond 48-72 Hours

Consider GERD management strategies:

• Trial of maternal elimination diet (restrict milk and eggs for 2-4 weeks) in breastfeeding mothers 3
• Reduce feeding volume while increasing frequency 3
• Keep infant upright after feeds (only when awake and supervised) 3

Diagnostic evaluation if symptoms persist or worsen:

• Regular weight checks are essential - poor weight gain warrants more aggressive intervention 1
• Upper GI imaging or endoscopy reserved for failure to respond to conservative measures or presence of alarm symptoms 3

Common Pitfalls to Avoid

• Do not assume all vomiting is benign reflux - always assess for red flags first 3, 4
• Do not withhold breastfeeding - this is the single most important intervention 3, 1
• Do not overprescribe acid suppressants - there is significant concern about overprescription of proton pump inhibitors in infants 3
• Do not miss bilious vomiting - this is a surgical emergency until proven otherwise 1, 2
• Do not delay surgical consultation if obstruction is suspected - conditions like volvulus can cause bowel necrosis within hours 6