Question:medium
What is the metabolic finding seen in a baby with CHPS (Congenital Hypertrophic Pyloric Stenosis)?
What is the metabolic finding seen in a baby with CHPS (Congenital Hypertrophic Pyloric Stenosis)?
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Think about what is lost when a baby repeatedly vomits gastric acid.
Updated On: Jun 23, 2026
- Hyperchloremic hypernatremic metabolic alkalosis
- Hypochloremic hypernatremic metabolic acidosis
- Hypochloremic hyponatremic metabolic alkalosis
- Hyperchloremic hyponatremic metabolic alkalosis
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The Correct Option is C
Solution and Explanation
In CHPS, the infant vomits gastric contents repeatedly. Gastric juice contains HCl, so loss of HCl leads to: loss of $H^+$ (metabolic alkalosis) and loss of $Cl^-$ (hypochloremia). Volume contraction triggers aldosterone release, which causes renal Na+ retention at the expense of K+ and H+, producing hyponatremia and hypokalemia. The combined result is hypochloremic, hyponatremic metabolic alkalosis. Key associations: MC surgical cause of vomiting in infants; age of presentation ~4 weeks; olive-shaped epigastric mass on palpation. \[\boxed{\text{Hypochloremic hyponatremic metabolic alkalosis (Option C)}}\]
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