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Infantile hypertrophic pyloric stenosis

Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Pyloric stenosis article more useful, or one of our other health articles.

Synonyms: congenital hypertrophic pyloric stenosis, hypertrophic pyloric stenosis

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This condition is caused by diffuse hypertrophy and hyperplasia of the smooth muscle of the antrum of the stomach and pylorus. It usually occurs in infants aged 2-8 weeks. The pyloric muscle hypertrophy results in narrowing of the pyloric canal, which can then become easily obstructed1 .

Genetic studies have identified susceptibility loci for infantile hypertrophic pyloric stenosis (IHPS) and molecular studies have concluded that smooth muscle cells are not properly innervated in this condition2 .


  • The incidence of pyloric stenosis is 2 to 5 in 1,000 live births per year.

  • It is more common in males, with a male:female ratio of 4:1.

  • There is a familial link, with a polygenic hereditary pattern.

  • Pyloric stenosis is more common in the white population. It is less commonly seen in Indian, Asian and Black populations.

  • HPS occurs very rarely in adults and must then be differentiated from gastric cancer4 .

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  • Typical presentation is onset of vomiting at 2-8 weeks of age (late presentation up to 6 months can occur but is very rare)5 6 :

    • Vomiting: non-bilious, often but not always projectile and usually 30-60 minutes after a feed, with the baby remaining hungry.

    • Vomiting increases in frequency over several days.

    • Vomiting also increases in intensity until it becomes projectile.

    • Slight haematemesis may occur.

  • Persistent hunger, weight loss, dehydration, lethargy, and infrequent or absent bowel movements may be seen.

  • Stomach wall peristalsis may be visible.

  • An enlarged pylorus, classically described as an 'olive', may be palpated in the right upper quadrant or epigastrium of the abdomen:

    • The 'olive' is best palpated at the start of a feed but is often missed7 .

    • With the infant supine and the examiner on the child's left side, gently palpate the liver edge near the xiphoid process.

    • Then displace the liver superiorly; downward palpation should reveal the pyloric olive just on, or to the right of, the midline.

    • It should be possible to roll the pylorus beneath the examining finger.

Differential diagnosis

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  • Serum electrolytes (for correction of imbalances before surgical repair); there is often metabolic alkalosis with severe potassium depletion. However, biochemical disturbances are now much less common with earlier diagnosis7 .

  • Ultrasound is reliable and easily performed and has replaced barium studies as the main investigation8 . There is a normal variation of pylorus muscle measurements with age and gestation but ultrasound has a very high sensitivity and specificity9 .


  • Pre-operative management is directed at correcting the fluid deficiency and electrolyte imbalance.

  • Ramstedt's pyloromyotomy is easily performed and is associated with minimal complications.

  • Laparoscopic pyloromyotomy is also performed and is an effective alternative where suitable facilities are available. Time to achieve full enteral feeding has been found to be significantly shorter in those treated laparoscopically vs those having open pyloromyotomy10 .


  • Vomiting can lead to dehydration, weight loss, and severe electrolyte disturbance (hypokalaemic and hypochloraemic metabolic alkalosis).

  • Operative complications include mucosal perforation, continued postoperative bleeding (very rare), and persistent vomiting due to incomplete pyloromyotomy (rare).

  • Foveolar cell hyperplasia (FCH) has been reported as a rare cause of persistent gastric outlet obstruction in patients with IHPS11 . An extended pyloromyotomy is required to manage this.


  • Prognosis is excellent unless diagnosis is delayed and prolonged severe dehydration occurs.

  • Mortality is rare after pyloromyotomy.

Further reading and references

  1. Peters B, Oomen MW, Bakx R, et al; Advances in infantile hypertrophic pyloric stenosis. Expert Rev Gastroenterol Hepatol. 2014 Jul;8(5):533-41. doi: 10.1586/17474124.2014.903799. Epub 2014 Apr 10.
  2. Panteli C; New insights into the pathogenesis of infantile pyloric stenosis. Pediatr Surg Int. 2009 Dec;25(12):1043-52. Epub 2009 Sep 16.
  3. Garfield K, Sergent SR; Pyloric Stenosis. StatPearls, March 2020.
  4. Hellan M, Lee T, Lerner T; Diagnosis and therapy of primary hypertrophic pyloric stenosis in adults: case report and review of literature. J Gastrointest Surg. 2006 Feb;10(2):265-9.
  5. Hsu P, Klimek J, Nanan R; Infantile hypertrophic pyloric stenosis: does size really matter? J Paediatr Child Health. 2014 Oct;50(10):827-8. doi: 10.1111/j.1440-1754.2010.01778.x. Epub 2010 Jun 27.
  6. Taylor ND, Cass DT, Holland AJ; Infantile hypertrophic pyloric stenosis: has anything changed? J Paediatr Child Health. 2013 Jan;49(1):33-7. doi: 10.1111/jpc.12027. Epub 2012 Dec 2.
  7. Gotley LM, Blanch A, Kimble R, et al; Pyloric stenosis: a retrospective study of an Australian population. Emerg Med Australas. 2009 Oct;21(5):407-13. doi: 10.1111/j.1742-6723.2009.01218.x.
  8. Niedzielski J, Kobielski A, Sokal J, et al; Accuracy of sonographic criteria in the decision for surgical treatment in infantile hypertrophic pyloric stenosis. Arch Med Sci. 2011 Jun;7(3):508-11. doi: 10.5114/aoms.2011.23419. Epub 2011 Jul 11.
  9. Sivitz AB, Tejani C, Cohen SG; Evaluation of hypertrophic pyloric stenosis by pediatric emergency physician sonography. Acad Emerg Med. 2013 Jul;20(7):646-51. doi: 10.1111/acem.12163. Epub 2013 Jun 19.
  10. Ismail I, Elsherbini R, Elsaied A, et al; Laparoscopic vs. Open Pyloromyotomy in Treatment of Infantile Hypertrophic Pyloric Stenosis. Front Pediatr. 2020 Aug 21;8:426. doi: 10.3389/fped.2020.00426. eCollection 2020.
  11. Tan HL, Blythe A, Kirby CP, et al; Gastric foveolar cell hyperplasia and its role in postoperative vomiting in patients with infantile hypertrophic pyloric stenosis. Eur J Pediatr Surg. 2009 Apr;19(2):76-8. Epub 2009 Feb 25.

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