In neonates, vomiting may range from benign physiological regurgitation to a surgical emergency. A systematic approach is essential.

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1. Gastrointestinal Causes

A. Physiological / Functional

• Physiological gastroesophageal reflux (GER)
• Overfeeding
• Improper feeding technique
• Aerophagia (swallowed air)
• Delayed gastric emptying in preterm infants

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B. Gastrointestinal Obstruction

High Intestinal Obstruction

Bilious vomiting is a surgical emergency until proven otherwise.

Esophageal

• Esophageal atresia ± tracheoesophageal fistula
• Esophageal stricture
• Congenital esophageal stenosis

Gastric

• Pyloric stenosis (typically 2–8 weeks)
• Gastric volvulus
• Gastric outlet obstruction
• Antral web

Duodenal

• Duodenal atresia
• Duodenal stenosis
• Annular pancreas
• Malrotation with midgut volvulus
• Ladd bands

Jejunal/Ileal

• Jejunal atresia
• Ileal atresia
• Meconium ileus
• Meconium plug syndrome
• Small left colon syndrome

Colonic

• Hirschsprung disease
• Colonic atresia
• Anorectal malformations

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C. Inflammatory/Infectious GI Disease

Necrotizing Enterocolitis (NEC)

Common NICU cause:

• Vomiting
• Feed intolerance
• Abdominal distension
• Bloody stools

Spontaneous Intestinal Perforation

Enterocolitis

• Bacterial
• Viral
• Fungal

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2. Infectious Causes

Any neonatal sepsis can present with vomiting.

Systemic Sepsis

• Early-onset sepsis
• Late-onset sepsis

Common organisms:

• Group B Streptococcus
• Escherichia coli
• Listeria monocytogenes
• Klebsiella
• Enterobacter
• Staphylococcus aureus
• CoNS
• Candida

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CNS Infections

• Meningitis
• Encephalitis
• Brain abscess (rare)

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Urinary Tract Infection

A very important cause of unexplained vomiting.

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3. Metabolic and Endocrine Causes

Inborn Errors of Metabolism (IEM)

Consider especially when vomiting is associated with:

• Lethargy
• Acidosis
• Hyperammonemia
• Hypoglycemia

Disorders

Amino Acid Disorders

• Maple syrup urine disease
• Phenylketonuria
• Homocystinuria

Organic Acidemias

• Propionic acidemia
• Methylmalonic acidemia
• Isovaleric acidemia

Urea Cycle Disorders

• OTC deficiency
• CPS deficiency

Fatty Acid Oxidation Disorders

• MCAD deficiency
• VLCAD deficiency

Carbohydrate Disorders

• Galactosemia
• Hereditary fructose intolerance

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Electrolyte Disorders

• Hyponatremia
• Hypernatremia
• Hypokalemia
• Hyperkalemia
• Hypocalcemia
• Hypercalcemia
• Hypomagnesemia

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Glucose Disorders

• Hypoglycemia
• Hyperglycemia

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Endocrine Disorders

Congenital Adrenal Hyperplasia (salt-wasting)

• Vomiting
• Dehydration
• Shock

Adrenal insufficiency

Congenital hypothyroidism

Hyperthyroidism (rare)

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4. Neurological Causes

Raised intracranial pressure can cause vomiting.

Intracranial Hemorrhage

• Germinal matrix hemorrhage
• Intraventricular hemorrhage
• Subdural hemorrhage

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Hydrocephalus

• Congenital
• Post-hemorrhagic

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Hypoxic-Ischemic Encephalopathy

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CNS Malformations

• Dandy-Walker malformation
• Arnold-Chiari malformation

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Seizures

May manifest as feed intolerance and vomiting.

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5. Respiratory Causes

Severe respiratory distress

• Respiratory distress syndrome
• Pneumonia
• PPHN
• Congenital heart disease with heart failure

Mechanism:

• Increased swallowed air
• Gut hypoperfusion

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6. Cardiac Causes

Congenital Heart Disease

Particularly:

• Duct-dependent lesions
• Heart failure states

Examples:

• Coarctation of aorta
• Hypoplastic left heart syndrome
• Interrupted aortic arch

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Congestive Cardiac Failure

• Large VSD
• PDA
• Cardiomyopathy

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7. Drug-Related Causes

Maternal Drug Exposure

• Opioid withdrawal
• SSRI exposure

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NICU Medications

• Caffeine
• Theophylline
• Erythromycin
• Opioids
• Iron supplements
• Vitamin preparations

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8. Feeding-Related Causes

Feeding Intolerance

Common in preterm infants

Features:

• Vomiting
• Increased gastric residuals
• Abdominal distension

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Human Milk Fortifier Intolerance

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Formula Intolerance

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Cow’s Milk Protein Allergy

Can present with:

• Vomiting
• Blood in stool
• Poor weight gain

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9. Hepatobiliary and Pancreatic Causes

• Neonatal hepatitis
• Cholestasis
• Biliary atresia
• Pancreatitis (rare)
• Choledochal cyst

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10. Toxic Causes

• Medication overdose
• Hypervitaminosis
• Accidental toxin exposure

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Important NICU “Cannot Miss” Diagnoses

Any neonate with vomiting should be assessed urgently for:

1. Malrotation with midgut volvulus
2. Necrotizing enterocolitis (NEC)
3. Sepsis
4. Meningitis
5. Congenital adrenal hyperplasia
6. Inborn errors of metabolism
7. Intestinal atresia
8. Hirschsprung disease
9. Pyloric stenosis
10. Intracranial hemorrhage

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Practical NICU Approach

Bilious Vomiting

Think:

• Malrotation with volvulus
• Intestinal atresia
• Hirschsprung disease
• Meconium ileus
• NEC

→ Surgical consultation immediately.

Non-bilious Projectile Vomiting

Think:

• Pyloric stenosis
• GER
• Overfeeding

Vomiting + Abdominal Distension

Think:

• NEC
• Obstruction
• Sepsis

Vomiting + Shock

Think:

• Sepsis
• CAH
• Volvulus
• Metabolic disease

Vomiting + Lethargy/Seizures

Think:

• Meningitis
• IVH
• Hypoglycemia
• IEM
• Electrolyte disturbance

For NICU practice, the highest-yield etiologies are GER/overfeeding, feeding intolerance of prematurity, NEC, sepsis, malrotation-volvulus, intestinal obstruction, CAH, and inborn errors of metabolism. These account for most clinically significant neonatal vomiting presentations.