Pyloric stenosis: Difference between revisions
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==Background==
==Background==
*More common in males (5:1) & firstborn children (30%)
*Hypertrophy of the pyloric muscle causing gastric outlet obstruction
*Prematurity and macrolide use are also thought to be risk factors
*Most common surgical cause of vomiting in infants<ref name="sreedharan">Sreedharan R, Liacouras CA. Major symptoms and signs of digestive tract disorders. In: Kliegman RM, ed. ''Nelson Textbook of Pediatrics''. 21st ed. Elsevier; 2020.</ref>
*Most common surgical cause of vomiting in infants
*Typical presentation: 2-6 week old infant (range 1-5 months)
*The main diagnostic criterion is a measurement of more than 3 mm in thickness of the muscular layer.<ref>Dias, S et al Insights Imaging. 2012 Jun; 3(3): 247–250.</ref>  
*Incidence: ~2-4 per 1,000 live births
*Abnormal elongation of the canal is characterised as greater than 17 mm in length .<ref>Teele RL, Smith EH. Ultrasound in the diagnosis of idiopathic hypertrophic pyloric stenosis. N Engl J Med. 1977 May 19. 296(20):1149-50.</ref><ref>Sargent SK, Foote SL, Mooney DP, Shorter NA. The posterior approach to pyloric sonography. Pediatr Radiol. 2000 Apr. 30(4):256-7</ref>
*Male:female ratio = 4:1
*Risk factors: firstborn, male sex, family history, macrolide antibiotics (erythromycin) in first 2 weeks of life


==Clinical Features==
==Clinical Features==
*Symptoms usually begin between 3-6 weeks of age, rarely after 12 weeks
*'''Non-bilious, projectile vomiting''' — immediately after feeds
*[[Nausea and vomiting (peds)|Vomiting]], immediately postprandial, nonbilious, often projectile, but desires to feed ("hungry vomiter")
**Progressively worsening over days to weeks
*Palpable mass in in RUQ to epigastric region after vomiting, occasionally may see reverse peristaltic fluid wave across abdomen
**Infant is hungry after vomiting ("hungry vomiter")
*If untreated, will see signs of [[dehydration (peds)|dehydration]], weight loss, [[lethargy]], [[pediatric shock|shock]]
*Olive-shaped mass in right upper quadrant/epigastrium (palpable in ~70% with experienced examiner)
*Visible gastric peristaltic waves (left to right across upper abdomen)
*Signs of dehydration: poor skin turgor, depressed fontanelle, decreased urine output, lethargy
*Weight loss or poor weight gain
*Jaundice (in ~2% due to decreased hepatic glucuronyl transferase activity)


==Differential Diagnosis==
==Differential Diagnosis==
{{Pediatric abdominal pain DDX}}
*[[Gastroesophageal reflux]] (GER)
*[[Malrotation]] with [[Midgut volvulus|volvulus]] ('''bilious''' vomiting = surgical emergency)
*Formula intolerance / milk protein allergy
*[[Intussusception]] (typically older age 6-36 months)
*Adrenal crisis ([[Congenital adrenal hyperplasia|CAH]]) — can mimic metabolic findings
*Gastroenteritis
*Increased intracranial pressure
*Inborn errors of metabolism


==Evaluation==
==Evaluation==
[[File:Pyloric-stenosisLocal.jpg|thumb|Pyloric stenosis as seen on ultrasound in a 6 week old.]]
*Abdominal ultrasound — diagnostic study of choice
[[File:PS longitudinal Subramaniam.gif|thumbnail|Longitudinal view of thickened and elongated pylorus muscle<ref>http://www.thepocusatlas.com/pediatrics/</ref>]]
**Pyloric muscle thickness >=3 mm
*Labs may show [[hypokalemia]] and hypochloremic [[metabolic alkalosis]]
**Pyloric channel length >=15 mm
 
**Sensitivity and specificity >95%
===Imaging===
*Labs (critical to check before surgery):
''Primary test of choice''
**BMP: hypochloremic, hypokalemic metabolic alkalosis (classic finding)
*[[ultrasound: abdomen|Ultrasound]]: thickened (>3 mm) and elongated (>17 mm) pylorus ~ 95% Sn/Sp<ref>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.</ref>
**Loss of HCl from vomiting → paradoxical aciduria
 
**May also have hyponatremia and hypoglycemia
''Other tests that may show findings''
*Upper GI series (if US inconclusive): "string sign," "shoulder sign," "beak sign"
*[[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)


==Management==
==Management==
*[[IVF]]
*'''This is NOT a surgical emergency''' — correct electrolytes and dehydration FIRST
**Normal electrolytes and no evidence of dehydration
*IV fluid resuscitation
***5% dextrose with 0.25% NaCl and 2 meq KCl per 100 mL
**Initial: NS 20 mL/kg bolus, repeat as needed
**Moderate or severe dehydration
**Maintenance: D5 0.45% NS + 20 mEq/L KCl (after urine output established)
***Higher NaCl concentrations (0.5% to normal saline) and higher rates of administration (1.5 to 2 times maintenance)
**Goal: correct chloride, potassium, and alkalosis before surgery
**Ensure correction of bicarbonate level, as it may be a hypoventilation risk
*NPO, NGT for decompression if significant distension
*[[Nasogastric tube]]
*Surgical consultation for pyloromyotomy (Ramstedt procedure) — definitive treatment
*Surgery
**Laparoscopic approach is standard; very high success rate
**Can be delayed 24-36 hr to rehydrate infant and correct electrolytes
*Surgery should be delayed until electrolytes are corrected (target: Cl >100, HCO3 <30, K >3.5)
 
===Precautions===
*Ensure that kidneys are functional prior to giving [[potassium]]
*Do not give lactated ringers
**May lead to worsening alkalosis > apnea in infants


==Disposition==
==Disposition==
*Admission
*Admit for IV fluid resuscitation and surgical repair
*Pediatric surgery consultation


==See Also==
==See Also==
*[[Abdominal Pain (Peds)]]
*[[Vomiting (peds)]]
*[[Malrotation]]
*[[Intussusception]]
*[[Pediatric abdominal pain]]


==References==
==References==
<references/>
<references/>
[[Category:Pediatrics]]
[[Category:Pediatrics]]
[[Category:GI]]
[[Category:Gastroenterology]]
[[Category:Surgery]]

Latest revision as of 10:25, 22 March 2026

Background

  • Hypertrophy of the pyloric muscle causing gastric outlet obstruction
  • Most common surgical cause of vomiting in infants[1]
  • Typical presentation: 2-6 week old infant (range 1-5 months)
  • Incidence: ~2-4 per 1,000 live births
  • Male:female ratio = 4:1
  • Risk factors: firstborn, male sex, family history, macrolide antibiotics (erythromycin) in first 2 weeks of life

Clinical Features

  • Non-bilious, projectile vomiting — immediately after feeds
    • Progressively worsening over days to weeks
    • Infant is hungry after vomiting ("hungry vomiter")
  • Olive-shaped mass in right upper quadrant/epigastrium (palpable in ~70% with experienced examiner)
  • Visible gastric peristaltic waves (left to right across upper abdomen)
  • Signs of dehydration: poor skin turgor, depressed fontanelle, decreased urine output, lethargy
  • Weight loss or poor weight gain
  • Jaundice (in ~2% due to decreased hepatic glucuronyl transferase activity)

Differential Diagnosis

  • Gastroesophageal reflux (GER)
  • Malrotation with volvulus (bilious vomiting = surgical emergency)
  • Formula intolerance / milk protein allergy
  • Intussusception (typically older age 6-36 months)
  • Adrenal crisis (CAH) — can mimic metabolic findings
  • Gastroenteritis
  • Increased intracranial pressure
  • Inborn errors of metabolism

Evaluation

  • Abdominal ultrasound — diagnostic study of choice
    • Pyloric muscle thickness >=3 mm
    • Pyloric channel length >=15 mm
    • Sensitivity and specificity >95%
  • Labs (critical to check before surgery):
    • BMP: hypochloremic, hypokalemic metabolic alkalosis (classic finding)
    • Loss of HCl from vomiting → paradoxical aciduria
    • May also have hyponatremia and hypoglycemia
  • Upper GI series (if US inconclusive): "string sign," "shoulder sign," "beak sign"

Management

  • This is NOT a surgical emergency — correct electrolytes and dehydration FIRST
  • IV fluid resuscitation
    • Initial: NS 20 mL/kg bolus, repeat as needed
    • Maintenance: D5 0.45% NS + 20 mEq/L KCl (after urine output established)
    • Goal: correct chloride, potassium, and alkalosis before surgery
  • NPO, NGT for decompression if significant distension
  • Surgical consultation for pyloromyotomy (Ramstedt procedure) — definitive treatment
    • Laparoscopic approach is standard; very high success rate
  • Surgery should be delayed until electrolytes are corrected (target: Cl >100, HCO3 <30, K >3.5)

Disposition

  • Admit for IV fluid resuscitation and surgical repair
  • Pediatric surgery consultation

See Also

References

  1. ↑ Sreedharan R, Liacouras CA. Major symptoms and signs of digestive tract disorders. In: Kliegman RM, ed. Nelson Textbook of Pediatrics. 21st ed. Elsevier; 2020.
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