Snapshot A 6-week-old first-born baby boy presents with projectile vomiting after feedings over the last 24 hours. Mom says that he enjoys feeding, and even after he vomits, he appears eager and hungry. On physical exam, you palpate an olive-shaped mass in the epigastric region. Labs show blood pH 7.47 and potassium of 3.2 mmol/L. High Yield A newborn boy presents with projectile vomiting and is always hungry to eat more after vomiting. The vomit is non-bilious, and an olive shaped mass is palpable in the patients abdomen. The patient has been treated with erythromycin for an infection. next best step in management: IV fluids and correct electrolytes (or order a complete metabolic panel) best initial test: ultrasound with a target shape lesion most accurate test: ultrasound treatment: pyloromyotomy Introduction Congenital hypertrophy of the pyloric sphincter Prevents stomach from emptying contents into intestinal tract "gastric outlet obstruction" Epidemiology 1:500 births Males > females More common in first-borns Uncommon in children > 6 months old, most common within first 12 weeks of life ETIOLOGY Risk factors maternal history of pyloric stenosis erythromycin use Associated with transesophageal fistulas Presentation Symptoms infants feed well for first 2-3 weeks of life presents with non-bilious vomiting after most or every feeding progresses to projectile vomiting at 2 weeks-2 months of life can lead to severe malnutrition/dehydration may experience other symptoms including belching abdominal pain constant hunger weight loss/failure to thrive Physical exam palpable epigastric olive-shaped mass pathognomonic for the disorder visible peristaltic waves over the gastrum may have swollen abdomen indicated of starvation state IMAGING Barium studies may show narrow pyloric channel "string sign" or "pyloric beak" Ultrasound hypertrophic pylorus may be observed STUDIES Electrolytes metabolic alkalosis hypokalemia/hypochloremia secondary to recurrent emesis Differential Hiatal hernia, duodenal atresia, volvulus, meconium ileus, GERD, gastroenteritis, tracheoesophageal fistula Treatment Prevention there are no preventive measures available at this time Medical management Hydration via IV fluids indicated in all cases Normalize acid-base/electrolyte abnormalities potassium replacement is key indicated in all cases Surgical intervention pyloromyotomy indicated for surgical correction of defect Complications Failure to thrive Prognosis Very good to excellent Surgery relieves symptoms and child is usually eating within hours of surgery