What is the management approach for a 3-week-old infant presenting with forceful vomiting and abnormal exam findings?

Management of a 3-Week-Old Infant with Forceful Vomiting

A 3-week-old infant presenting with forceful vomiting requires immediate evaluation for hypertrophic pyloric stenosis, which is the most likely diagnosis given the age and symptom presentation. 1

Initial Assessment

• Hydration status evaluation:

  • Check for signs of dehydration: sunken fontanelle, decreased skin turgor, dry mucous membranes, decreased urine output
  • Assess for hypochloremic, hypokalemic metabolic alkalosis (typical in pyloric stenosis)

• Physical examination priorities:

  • Abdominal examination to detect a palpable "olive" (hypertrophic pyloric muscle)
  • Weight and growth parameters compared to baseline
  • Assessment of vital signs

Diagnostic Approach

1. Abdominal ultrasound - First-line imaging study with 95-100% sensitivity for pyloric stenosis

   • Look for pyloric muscle thickness >3mm and length >15mm 1

2. Laboratory studies if dehydration is present:

   • Electrolytes, BUN, creatinine to evaluate for metabolic alkalosis
   • CBC to assess for infection
   • Glucose level if hypoglycemia is suspected 1, 2

3. Upper GI series if ultrasound is negative but clinical suspicion remains high 1

Management Algorithm

1. If pyloric stenosis is confirmed:

   • NPO status
   • IV fluid resuscitation to correct dehydration and electrolyte abnormalities
   • Immediate surgical consultation for pyloromyotomy 1, 2

2. If gastroesophageal reflux disease (GERD) is diagnosed:

   • Parental reassurance and education about regurgitation
   • Smaller, more frequent feedings
   • Upright positioning for 30 minutes after feeding
   • Avoid medications unless symptoms are severe 3, 4

3. If acute gastroenteritis is suspected:

   • Oral rehydration therapy for mild to moderate dehydration
   • Consider ondansetron (0.2 mg/kg oral; 0.15 mg/kg parenteral; maximum 4 mg) if persistent vomiting prevents oral intake 2, 5
   • IV fluids for severe dehydration 5

Red Flags Requiring Immediate Attention

• Bilious vomiting (surgical emergency)
• Bloody vomiting
• Altered mental status
• Signs of shock or severe dehydration
• Inconsolable crying or excessive irritability 2, 6

Potential Pitfalls to Avoid

• Mistaking normal physiologic reflux for pathologic condition requiring medication 3
• Delaying surgical consultation when pyloric stenosis is suspected 1
• Using car seats or semi-reclined positions after feeding in cases of reflux 1
• Overlooking metabolic derangements from prolonged vomiting 2
• Failing to consider cow's milk protein allergy, which can co-exist with GERD in 42-58% of infants 4

Remember that while gastroesophageal reflux is common in infants, forceful (projectile) vomiting at 3 weeks of age strongly suggests pyloric stenosis until proven otherwise and requires prompt evaluation and management.