Projectile Vomiting in a 6-Month-Old Without Illness
A 6-month-old infant with projectile vomiting but no other signs of illness requires urgent evaluation for hypertrophic pyloric stenosis (HPS) as the primary concern, though this diagnosis is less common at this age and warrants consideration of alternative causes including extrinsic compression or gastroesophageal reflux disease. 1
Immediate Clinical Assessment
Key History and Physical Examination Elements
Determine if vomiting is bilious or non-bilious – bilious vomiting indicates obstruction distal to the ampulla of Vater and constitutes a surgical emergency requiring immediate intervention 1, 2
Palpate for the classic "olive" mass in the right upper quadrant – this finding is pathognomonic for HPS 1
Assess hydration status by evaluating:
Evaluate weight gain pattern – poor weight gain elevates concern for GERD disease rather than benign reflux and warrants more aggressive intervention 1
Assess stool and gas passage – regular passage argues strongly against mechanical obstruction 1
Age-Specific Considerations
At 6 months of age, HPS is uncommon but not impossible. HPS typically presents between 2-8 weeks of age, making it quite rare in older infants 1, 3. Children presenting with projectile vomiting after 6 months should be thoroughly investigated for causes other than typical intrinsic HPS, including extrinsic compression from bands or other anatomical variants 3.
Diagnostic Approach
Initial Imaging Strategy
Abdominal ultrasound is the modality of choice for suspected HPS in infants older than 2 weeks with non-bilious projectile vomiting 1, 2
Abdominal X-ray should be obtained if signs of intestinal obstruction are present (abdominal distension, bilious vomiting) 1, 2
Upper GI series may be appropriate for suspected uncomplicated gastroesophageal reflux, though imaging is often not necessary if the infant is gaining weight appropriately 1
Red Flags Requiring Urgent Evaluation
- Bilious (green) vomiting 1, 2
- Blood in vomit or stool 1
- Abdominal distension 1, 2
- Weight loss or poor weight gain 1
- Lethargy or altered mental status 1, 2
- Decreased urine output 1
Management Algorithm
If Mechanical Obstruction Suspected (HPS or Other)
- Withhold feeds temporarily 1
- Ensure adequate hydration with IV fluids if dehydration is present or oral intake is not tolerated 1
- Obtain immediate surgical consultation if HPS or other mechanical obstruction is confirmed or strongly suspected 1
If Non-Obstructive Cause Likely (GERD)
Continue breastfeeding on demand if breast-fed – breast milk should not be interrupted 1
Continue full-strength formula immediately in amounts sufficient to satisfy energy requirements for formula-fed infants 1
Administer oral rehydration solution (ORS) in small, frequent volumes (5 mL every minute initially) using a spoon or syringe if any dehydration present 1
Replace each vomiting episode with 10 mL/kg of ORS 1
Consider trial of smaller, more frequent feeds and feed thickening agents for GERD 1
Medication Considerations
Antiemetics are generally NOT indicated for routine management in infants this young 1. Ondansetron (0.2 mg/kg oral, maximum 4 mg) may be considered only if persistent vomiting prevents oral intake entirely 1.
Antidiarrheal or antimotility agents should NOT be used as these can cause serious side effects and are not effective 1.
Common Pitfalls
Assuming HPS is unlikely due to age – while rare after 6 months, extrinsic causes of pyloric stenosis can occur and mimic HPS 3
Delaying evaluation of bilious vomiting – this is a surgical emergency until proven otherwise 2
Failing to maintain vigilance for change in vomiting pattern – malrotation with volvulus can present at any age, not just in newborns 1
Overlooking dehydration – regular assessment and aggressive rehydration are essential 1
Follow-Up Instructions
Instruct parents to return immediately or call if: