GERD and Peptic Ulcer Disease USMLE Step 1 Practice Question
A 4-week-old firstborn boy presents with projectile nonbilious vomiting after feeds for 3 days. Vital signs show HR 152/min, RR 28/min, BP 78/52 mmHg, and temperature 37.2°C. Physical examination reveals visible peristaltic waves and a palpable olive-shaped mass in the epigastrium. Laboratory studies demonstrate serum chloride 92 mEq/L and potassium 3.1 mEq/L. There is no bilious drainage. Which acid-base abnormality is most likely present?
Answer choices
- ANormal acid-base status
- BMetabolic acidosis with hyperkalemia
- CHigh anion gap metabolic acidosis
- DHypochloremic metabolic alkalosisCorrect answer
- ERespiratory acidosis with hypochloremia
- FHypokalemic metabolic acidosis with elevated anion gap
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