Non-bilious projectile vomiting in a young infant

Specialty: Pediatrics.

• Explosive postprandial vomiting
• suspected hypertrophic pyloric stenosis

Why it occurs

• Hypertrophic pyloric stenosis (HPE, progressive hypertrophy and hyperplasia of the circular musculature of the pylorus that obstructs the gastric outlet, typical in infants 2 to 8 weeks of age)
• Severe physiological gastroesophageal reflux or allergy to cow's milk proteins (with gastric irritation and reactive pyloric spasm)
• Acute gastroenteritis in the initial phase (gastric viral infection that produces repeated emesis, although rarely in constant projectile form)
• Innate error of metabolism with acidosis or hyperammonemia (urea cycle disorders or organic acidemias that present with early onset vomiting)
• Intracranial hypertension or infant meningitis (vomiting of central origin, not preceded by nausea, accompanied by extreme irritability or tense fontanel)

Initial workup

High-resolution abdominal ultrasound (gold standard for the diagnosis of hypertrophic pyloric stenosis; confirms the diagnosis if the thickness of the pyloric muscle is greater than or equal to 3 mm and the length of the pyloric canal is greater than or equal to 15-17 mm). Capillary gasometry and determination of serum electrolytes (potassium, sodium, chlorine) to identify the presence of hypochloremic metabolic alkalosis. Esophagogastric transit with diluted barium or water-soluble contrast if ultrasound is inconclusive (revealing the "string" or "umbrella" sign).

Standard management

• Antiemetics such as Metoclopramide or Ondansetron should not be administered to infants suspected of mechanical pyloric obstruction or children under one year of age without specific indication, due to the risk of extrapyramidal effects or clinical masking. The curative treatment of EHP is surgical through Ramstedt pyloromyotomy. Prior to surgery, dehydration and electrolyte disorders must be comprehensively corrected by intravenous infusion of 0.9% Physiological Serum or 5-10% Glucosated Serum with contributions of sodium chloride and potassium chloride, until the pH and serum chloride levels are normalized.