A 3-week-old male infant presents with projectile non-bilious vomiting, visible gastric peristalsis, and an olive-shaped mass in the epigastrium. Ultrasound shows pyloric muscle thickness of 4.5 mm and channel length of 18 mm. What is the metabolic derangement and definitive treatment?
- A Hyperchloremic metabolic acidosis; emergency pyloromyotomy
- B Hyponatremic dehydration; IV sodium and immediate surgery
- C Normal metabolic state; laparoscopic fundoplication for gastroesophageal reflux
- D Hypochloremic hypokalemic metabolic alkalosis; correct electrolytes then Ramstedt's pyloromyotomy ✓
Explanation
Hypertrophic pyloric stenosis causes loss of gastric HCl through repeated vomiting, producing hypochloremic hypokalemic metabolic alkalosis (paradoxical aciduria in severe cases as kidneys preferentially conserve Na+ and H2O at the expense of H+ and K+). Ultrasound criteria for diagnosis: muscle wall thickness ≥4 mm, channel length ≥17 mm. Pyloromyotomy is the definitive treatment, but it is NOT an emergency — life-threatening metabolic derangement must first be corrected with IV normal saline + KCl supplementation. Ramstedt's pyloromyotomy (open or laparoscopic) divides the hypertrophied muscle longitudinally without entering the mucosa.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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Written and medically reviewed by the StethoPrep medical team.