A 26-day-old male infant presents with non-bilious projectile vomiting after every feed for 5 days. He is hungry after vomiting. A palpable olive-shaped mass is felt in the right hypochondrium. Serum electrolytes show Na+ 136, K+ 2.8, Cl- 88, HCO3- 34. Which is the characteristic pattern of acid-base disturbance in this infant?
- A Metabolic acidosis with normal anion gap
- B Respiratory alkalosis with hypokalemia
- C Metabolic alkalosis with paradoxical aciduria ✓
- D Mixed metabolic and respiratory acidosis
Correct answer: C. Metabolic alkalosis with paradoxical aciduria
Explanation
The infant has infantile hypertrophic pyloric stenosis, which causes loss of HCl-rich gastric juice through persistent vomiting, producing hypochloremic metabolic alkalosis. The kidneys attempt to conserve sodium by exchanging it for hydrogen in the distal tubule, producing paradoxical aciduria despite systemic alkalosis. This is a classic association described in pediatric surgery texts.
Reference: Bailey and Love's Short Practice of Surgery, 27th ed.
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Written and medically reviewed by the StethoPrep medical team.