Infantile Hypertrophic Pyloric Stenosis

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

See also: Pyloric Stenosis written for patients

Synonyms: congenital hypertrophic pyloric stenosis, hypertrophic pyloric stenosis

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 obstructed.[1] 

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 condition.[2]

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  • The incidence is variable with different regions. The incidence has been found to occur in 1 in 500 live births.[3] However, the incidence may be as high as 1 in 200 live births in some regions.
  • It is more common in males than in females (male:female ratio 4:1). First-born male children are believed to have the highest risk.
  • Early exposure to oral erythromycin in young infants, particularly in the first two weeks of life, has been associated with the development of hypertrophic pyloric stenosis (HPS).[4] 
  • HPS occurs very rarely in adults and must then be differentiated from gastric cancer.[5]
  • Typical presentation is onset of vomiting at 2-8 weeks of age (late presentation up to 6 months can occur but is very rare):[6][7] 
    • 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 missed.[8] 
    • 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.
  • 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 diagnosis.[8] 
  • Ultrasound is reliable and easily performed and has replaced barium studies as the main investigation.[9] There is a normal variation of pylorus muscle measurements with age and gestation but ultrasound has a very high sensitivity and specificity.[10] 
  • 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.[11]
  • Laparoscopic pyloromyotomy is also performed and is an effective alternative where suitable facilities are available.[12] 
  • Time to achieve full enteral feeding has been found to be significantly shorter (18.5 hours) in those treated laparoscopically vs those having open pyloromyotomy (23.9 hours).[13]
  • Double-Y pyloromyotomy has also been safely and effectively performed.[14]
  • 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 IHPS.[15] 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 & 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. de Laffolie J, Turial S, Heckmann M, et al; Decline in infantile hypertrophic pyloric stenosis in Germany in 2000-2008. Pediatrics. 2012 Apr;129(4):e901-6. doi: 10.1542/peds.2011-2845. Epub 2012 Mar 19.
  4. Lozada LE, Royall MJ, Nylund CM, et al; Development of pyloric stenosis after a 4-day course of oral erythromycin. Pediatr Emerg Care. 2013 Apr;29(4):498-9. doi: 10.1097/PEC.0b013e31828a3663.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. Aspelund G, Langer JC; Current management of hypertrophic pyloric stenosis. Semin Pediatr Surg. 2007 Feb;16(1):27-33.
  12. Carrington EV, Hall NJ, Pacilli M, et al; Cost-effectiveness of laparoscopic versus open pyloromyotomy. J Surg Res. 2012 Nov;178(1):315-20. doi: 10.1016/j.jss.2012.01.031. Epub 2012 Mar 27.
  13. Hall NJ, Pacilli M, Eaton S, et al; Recovery after open versus laparoscopic pyloromyotomy for pyloric stenosis: a Lancet. 2009 Jan 31;373(9661):390-8. Epub 2009 Jan 18.
  14. Alalayet YF, Miserez M, Mansoor K, et al; Double-Y pyloromyotomy: a new technique for the surgical management of infantile Eur J Pediatr Surg. 2009 Feb;19(1):17-20. Epub 2009 Feb 16.
  15. Tan HL, Blythe A, Kirby CP, et al; Gastric foveolar cell hyperplasia and its role in postoperative vomiting in Eur J Pediatr Surg. 2009 Apr;19(2):76-8. Epub 2009 Feb 25.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Colin Tidy
Current Version:
Peer Reviewer:
Dr Adrian Bonsall
Document ID:
1455 (v23)
Last Checked:
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