MEDizzy - A 4-week-old male infant presents with projectile,

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Pediatric Surgery II

A 4-week-old male infant presents with projectile, nonbilious emesis. Ultrasound of the abdomen reveals a pyloric muscle thickness of 8 mm (normal 3-4 mm). Which of the following is the best initial management of this patient?

ExplanationD. The patient’s symptoms and findings on ultrasound are consistent with hypertrophic pyloric stenosis. The treatment is pyloromyotomy (a partial-thickness cut at the pylorus through muscle but not mucosa) after fluid resuscitation and correction of electrolyte and acid– base abnormalities. Loss of gastric hydrochloric acid with vomiting results in a hypokalemic, hypochloremic, metabolic alkalosis. Before surgery, it is important to hydrate the infant and slowly correct the metabolic alkalosis with normal saline. Because the compensatory mechanism for metabolic alkalosis is hypoventilation/respiratory acidosis, correction is necessary to prevent postoperative apnea. Dehydration initially results in loss of bicarbonate in the urine to maintain a normal pH. However, because the renal mechanism for restoring volume status is aldosterone-mediated, hydrogen and potassium ions are excreted in the urine when sodium is reabsorbed leading to “paradoxical aciduria” (in the setting of alkalosis). Administration of bicarbonate is therefore not indicated.