Pyloric stenosis

(Redirected from Pyloric Stenosis)


Outline of stomach, showing its anatomical landmarks, including the pylorus.
  • More common in males (5:1) & firstborn children (30%)
  • Prematurity and macrolide use are also thought to be risk factors
  • Most common surgical cause of vomiting in infants
  • The main diagnostic criterion is a measurement of more than 3 mm in thickness of the muscular layer on ultrasound.[1]
  • Abnormal elongation of the canal is characterised as greater than 17 mm in length .[2][3]

Clinical Features

  • Symptoms usually begin between 3-6 weeks of age, rarely after 12 weeks
  • Vomiting, immediately postprandial, nonbilious, often projectile, but desires to feed ("hungry vomiter")
  • Palpable mass in in RUQ to epigastric region after vomiting, occasionally may see reverse peristaltic fluid wave across abdomen
  • If untreated, will see signs of dehydration, weight loss, lethargy, shock

Differential Diagnosis

Pediatric Abdominal Pain

0–3 Months Old

3 mo–3 y old

3 y old–adolescence


Pyloric stenosis as seen on ultrasound in a 6 week old.
Longitudinal view of thickened and elongated pylorus muscle[4]


Primary test of choice

  • Ultrasound: thickened (>3 mm) and elongated (>17 mm) pylorus ~ 95% Sn/Sp[5]

Other tests that may show findings

  • Abdominal x-ray: may show large stomach bubble with absence of air in small bowel or colon
    • Characteristic caterpillar sign (gastric contractions against hypertrophied pylorus)
  • Upper GI: string sign (narrowed pyloric lumen), double track sign (duplicated mucosa), beak sign (abnormality of pyloric opening)


  • IVF
    • Normal electrolytes and no evidence of dehydration
      • 5% dextrose with 0.25% NaCl and 2 meq KCl per 100 mL
    • Moderate or severe dehydration
      • Higher NaCl concentrations (0.5% to normal saline) and higher rates of administration (1.5 to 2 times maintenance)
    • Ensure correction of bicarbonate level, as it may be a hypoventilation risk
  • Nasogastric tube
  • Surgery
    • Can be delayed 24-36 hr to rehydrate infant and correct electrolytes


  • Ensure that kidneys are functional prior to giving potassium
  • Do not give lactated ringers
    • May lead to worsening alkalosis > apnea in infants


  • Admission

See Also


  1. Dias, S et al Insights Imaging. 2012 Jun; 3(3): 247–250.
  2. Teele RL, Smith EH. Ultrasound in the diagnosis of idiopathic hypertrophic pyloric stenosis. N Engl J Med. 1977 May 19. 296(20):1149-50.
  3. Sargent SK, Foote SL, Mooney DP, Shorter NA. The posterior approach to pyloric sonography. Pediatr Radiol. 2000 Apr. 30(4):256-7
  5. Rohrschneider WK, Mittnacht H, Darge K, Tröger J. Pyloric muscle in asymptomatic infants: sonographic evaluation and discrimination from idiopathic hypertrophic pyloric stenosis. Pediatr Radiol. 1998 Jun;28(6):429-34.