What is the initial workup for a 2-month-old infant presenting with vomiting in the emergency department (ED)?

Initial Workup for a 2-Month-Old Infant with Vomiting in the ED

The initial workup for a 2-month-old infant presenting with vomiting in the emergency department should begin with a thorough clinical evaluation including history and physical examination, followed by appropriate imaging based on the presentation, with abdominal radiography being the first-line imaging study if obstruction is suspected. 1

Clinical Assessment

History - Key Elements to Obtain

• Nature of vomiting (bilious vs. non-bilious) - bilious vomiting indicates obstruction distal to the ampulla of Vater and requires urgent evaluation 2
• Timing and frequency of vomiting episodes 1
• Associated symptoms (fever, diarrhea, irritability, lethargy) 1
• Feeding patterns and recent changes 3
• Stool characteristics (bloody, "currant jelly" appearance) 2
• Urine output (to assess hydration status) 4

Physical Examination - Critical Components

• Vital signs (including temperature, heart rate, respiratory rate) 3
• Hydration status assessment using the Clinical Dehydration Scale 4
• Abdominal examination (distention, tenderness, palpable masses - particularly the "olive" of hypertrophic pyloric stenosis) 1
• Neurological assessment (bulging fontanelle, altered mental status) 1
• Examination of genitalia and hernial orifices 5
• Fundoscopic examination (for papilledema suggesting increased intracranial pressure) 5

Red Flag Signs Requiring Immediate Attention

• Bilious vomiting (surgical emergency until proven otherwise) 2
• Bloody vomitus 5
• Signs of shock or severe dehydration 4
• Altered mental status or neurological signs 1
• Abdominal distention or signs of obstruction 1
• Inconsolable crying or excessive irritability 3

Initial Diagnostic Workup

Laboratory Studies (if dehydration or red flags present)

• Serum electrolytes and blood gases 3
• Renal and liver function tests 3
• Blood glucose (to rule out hypoglycemia) 3
• Consider metabolic studies if inborn errors of metabolism are suspected 3

Imaging Studies

• For infants with suspected obstruction: Abdominal radiography is the appropriate initial imaging study 1
• For infants older than 2 weeks with non-bilious vomiting: Ultrasound of the abdomen (UGI tract) is recommended to evaluate for hypertrophic pyloric stenosis 1
• For infants with bilious vomiting: Upper GI series is the appropriate next step after initial assessment 1

Management Algorithm Based on Presentation

For Non-Bilious Vomiting Without Red Flags

1. Assess hydration status 4
2. For mild dehydration: Oral rehydration therapy with small, frequent volumes (5 mL every minute) 1
3. Continue breastfeeding for breastfed infants 1
4. For formula-fed infants: Consider full-strength, lactose-free formulas if available 1
5. Consider ultrasound if pyloric stenosis is suspected (especially in infants 2 weeks to 3 months) 1

For Bilious Vomiting or Red Flags Present

1. Immediate surgical consultation 2
2. NPO (nothing by mouth) and nasogastric tube decompression 3
3. IV fluid resuscitation if moderate to severe dehydration 4
4. Abdominal radiography followed by upper GI series 1
5. Additional imaging based on radiographic findings 1

Common Pitfalls to Avoid

• Assuming all vomiting is due to gastroenteritis without ruling out surgical causes 3
• Delaying evaluation of bilious vomiting (surgical emergency until proven otherwise) 2
• Failing to recognize signs of increased intracranial pressure 1
• Overlooking hypertrophic pyloric stenosis in infants 2 weeks to 3 months of age 1
• Administering antiemetics before establishing diagnosis (may mask important symptoms) 5

Remember that while viral gastroenteritis is common, in a 2-month-old infant, serious conditions such as malrotation with volvulus, pyloric stenosis, intussusception, and metabolic disorders must be considered and ruled out promptly 1, 3.