What are the differential diagnoses and recommended workup for a 14‑month‑old presenting to urgent care with five episodes of vomiting today?

Acute Vomiting in a 14-Month-Old: Differential Diagnosis and Workup

Begin with an immediate assessment for red-flag features—bilious vomiting, bloody emesis, severe dehydration, toxic appearance, altered mental status, or abdominal distension—because these indicate surgical emergencies or life-threatening systemic illness that require urgent intervention. 1

Immediate Red-Flag Assessment

Perform a focused evaluation for the following critical features:

• Bilious vomiting (green or yellow-green emesis) indicates obstruction distal to the ampulla of Vater and is a surgical emergency until proven otherwise; malrotation with midgut volvulus can cause intestinal necrosis within hours. 1, 2
• Bloody vomitus or "currant-jelly" stools suggest intussusception, which peaks between 6–18 months and presents with intermittent crampy abdominal pain, lethargy, and a palpable mass. 1, 2
• Toxic appearance with fever may indicate sepsis, meningitis, bacterial pneumonia, or urinary tract infection requiring immediate recognition and treatment. 1
• Severe dehydration (≥10% fluid deficit) manifested by prolonged skin tenting >2 seconds, cool extremities, decreased capillary refill, and lethargy mandates immediate intravenous fluid resuscitation. 1
• Altered mental status or neurologic signs raise concern for increased intracranial pressure from trauma, hydrocephalus, or meningitis. 3

Hydration Status Evaluation

Stratify dehydration clinically:

• Mild (3–5% deficit): increased thirst, slightly dry mucous membranes. 1
• Moderate (6–9% deficit): loss of skin turgor, dry mucous membranes. 1
• Severe (≥10% deficit): lethargy, prolonged skin tenting >2 seconds, cool extremities, reduced capillary refill. 1

Differential Diagnosis by Clinical Pattern

Non-Bilious Vomiting Without Red Flags

Viral gastroenteritis is the most common cause in this age group, typically presenting with sudden onset of vomiting, watery diarrhea, mild fever, and a relatively short duration, often occurring in epidemics. 3, 1

Other considerations include:

• Systemic infections: otitis media, pneumonia, urinary tract infection, or sepsis can present with vomiting and fever. 3, 1
• Gastroesophageal reflux (GER): typically presents with intermittent regurgitation from birth and normal weight gain; forceful projectile vomiting is not consistent with simple GER. 1, 4
• Metabolic disorders: phenylketonuria, hyperammonemia, galactosemia, diabetes, or adrenocortical hyperplasia may present with vomiting. 3
• Toxic ingestions or trauma: always consider in the differential. 3

Bilious Vomiting (Surgical Emergency)

• Malrotation with midgut volvulus: accounts for 20% of bilious vomiting cases and can occur at any age, though most commonly in newborns; requires immediate upper GI series. 1, 2, 4
• Intussusception: presents with intermittent crampy abdominal pain (manifested as inconsolable crying or drawing up of legs), progression to bilious vomiting, "currant-jelly" stools, and lethargy; most common between 6–18 months. 3, 1, 2
• Other obstructions: less common at this age but include incarcerated hernia, adhesions, or foreign body. 3

Forceful Projectile Non-Bilious Vomiting

• Hypertrophic pyloric stenosis (HPS): typically presents between 3–6 weeks of age (not 14 months), but atypical late presentations can occur; characterized by progressive forceful projectile vomiting, palpable "olive" mass in the right upper quadrant, and hypochloremic hypokalemic metabolic alkalosis. 3, 1, 4

Recommended Workup

History and Physical Examination

Document the following:

• Vomitus characteristics: bilious (green/yellow-green), bloody, projectile, or non-bilious. 1
• Stool pattern: bloody, "currant-jelly," watery, or absent. 1
• Associated symptoms: fever, abdominal pain, altered mental status, toxic appearance, or lethargy. 1
• Recent exposures: recent antibiotics (risk of C. difficile), daycare attendance (risk of Giardia, Shigella), foreign travel. 1
• Abdominal exam: distension, tenderness, masses (especially right upper quadrant "olive" or sausage-shaped mass), bowel sounds, and hernial orifices. 1, 5
• Neurologic exam: altered mental status, bulging fontanelle (if still open), papilledema. 3, 1

Laboratory Studies

• Stool cultures are indicated when any of the following are present: bloody diarrhea, white blood cells on stool stain, recent antibiotic use, daycare exposure, recent travel, or immunodeficiency. 1
• Serum electrolytes, blood gases, renal and liver function tests are required in any child with dehydration or red-flag signs. 5
• Blood cultures and urinalysis if systemic infection is suspected. 1

Imaging Studies

The imaging pathway depends entirely on the presence or absence of bilious vomiting and clinical suspicion for obstruction or intussusception:

For Bilious Vomiting or Suspected Obstruction

• Obtain an abdominal radiograph immediately as the first imaging study to identify obstruction patterns (dilated loops, air-fluid levels, "double-bubble" or "triple-bubble" signs). 1, 2
• Perform an upper GI series urgently if bilious vomiting is present with non-classic radiographic findings or if malrotation with volvulus is suspected; plain films miss up to 7% of malrotation cases. 1, 2

For Suspected Intussusception

• Ultrasound is the initial imaging modality of choice when clinical features (intermittent crampy pain, "currant-jelly" stools, lethargy, palpable mass) raise suspicion for intussusception. 1, 2

For Non-Bilious Vomiting Without Red Flags

• No imaging is required for clear viral gastroenteritis (watery diarrhea, vomiting, child <2 years, normal exam). 1
• Imaging is not indicated for uncomplicated GER when the infant demonstrates normal weight gain and lacks progressive projectile vomiting. 1

Management

Viral Gastroenteritis (Most Likely Diagnosis)

• Oral rehydration therapy (ORT) is the cornerstone of treatment; begin early refeeding with an age-appropriate diet once the child is rehydrated. 1
• Antimicrobials are NOT indicated for watery diarrhea and vomiting in children <2 years, as the condition is most often viral. 1
• Antidiarrheal agents (e.g., loperamide, kaolin-pectin) are contraindicated because they do not reduce stool volume or duration and can cause severe abdominal distention, ileus, and even death. 1
• Ondansetron (0.2 mg/kg oral; maximum 4 mg) may be used for children unable to take oral fluids due to persistent vomiting, but should not replace proper fluid and electrolyte management. 1, 5

Surgical Emergencies

• Immediate pediatric surgery consultation is mandatory for any bilious vomiting, suspected intussusception, or signs of bowel obstruction. 2, 4
• Stop oral fluids/feeds and decompress the stomach with a nasogastric tube in patients with bilious vomiting. 5
• IV fluid resuscitation is required for severe dehydration or surgical conditions. 1, 4

Critical Pitfalls to Avoid

• Never dismiss bilious vomiting as "just gastroenteritis"—it is a surgical emergency until proven otherwise. 1, 2
• Do not delay imaging if clinical suspicion for obstruction or intussusception is high—progression can lead to bowel necrosis, perforation, or death. 2, 4
• Infants have a higher risk of dehydration due to a larger body-surface-to-weight ratio, higher metabolic rate, and reliance on caregivers for fluid intake; reassess hydration status frequently. 1
• Always reassess for progression to bilious vomiting—this changes the diagnosis to a more urgent surgical emergency. 2, 4