A patient with high jejunal obstruction and repeated projectile vomiting is expected to develop which acid-base and electrolyte pattern?

• A Hyperchloraemic metabolic acidosis from loss of bicarbonate-rich fluid
• B Hypochloraemic, hypokalaemic metabolic alkalosis from loss of hydrochloric acid and potassium in gastric juice ✓
• C Normal anion gap metabolic acidosis with compensatory hyperkalaemia
• D Respiratory alkalosis from hyperventilation secondary to pain

Explanation

Proximal obstruction causes loss of gastric juice rich in hydrogen, chloride, and potassium, producing hypochloraemic hypokalaemic metabolic alkalosis, classically worsened by aldosterone-driven renal potassium wasting. Loss of bicarbonate-rich distal secretions, as in diarrhoea or distal fistula, produces metabolic acidosis instead, which is what makes option A the classic trap here.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.