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Key Features

  • Postnatal muscular hypertrophy of the pylorus

  • Progressive gastric outlet obstruction, nonbilious vomiting, dehydration, and alkalosis in infants younger than 12 weeks

  • Upper GI contrast radiographs or abdominal ultrasound are diagnostic

  • Cause is unknown.

  • Incidence is 1–8 per 1000 births, with a 4:1 male predominance

  • Studies suggest that erythromycin given in the neonatal period is associated with a higher incidence of pyloric stenosis

Clinical Findings

  • Onset of symptoms may be delayed in preterm infants

  • Vomiting starts at birth in about 10% of cases

  • Projectile postprandial vomiting

    • Usually begins between 2 and 4 weeks of age

    • May start as late as 12 weeks

  • Vomitus is rarely bilious but may be blood-streaked

  • Infants are usually hungry and nurse avidly

  • Upper abdomen may be distended after feeding

  • Prominent gastric peristaltic waves from left to right may be seen

  • An oval mass can be felt on deep palpation in the right upper abdomen, especially after vomiting

    • Measures 5–15 mm in longest dimension

    • However, only present in 13.6% of patients studied


  • Hypochloremic alkalosis with potassium depletion is classic metabolic finding

  • Dehydration causes elevated hemoglobin and hematocrit

  • Mild unconjugated bilirubinemia occurs in 2–5% of cases

  • Ultrasonography shows a hypoechoic muscle ring greater than 4 mm thickness with a hyperdense center and a pyloric channel length > 15 mm

  • Barium upper GI series

    • Reveals retention of contrast in the stomach and a long narrow pyloric channel with a double track of barium

    • Postoperative radiograph remains abnormal for many months despite relief of symptoms


  • Treat dehydration and electrolyte imbalance before surgery, even if it takes 24–48 hours

  • Ramstedt pyloromyotomy

    • Treatment of choice

    • Consists of incision down to the mucosa along the pyloric length

    • Can be performed laparoscopically, with similar efficacy

  • Outlook after surgery is excellent

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