Infantile hypertrophic pyloric stenosis

Synonyms: congenital hypertrophic pyloric stenosis, hypertrophic pyloric stenosis

What is infantile hypertrophic pyloric stenosis?

Infantile hypertrophic pyloric stenosis is the hypertrophy of the pylorus, causing obstruction of the passage of milk from the stomach to the duodenum.

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

• 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 Asian and Black populations.

• Typical presentation is onset of vomiting at 2-8 weeks of age (late presentation up to 6 months can occur but is very rare):^{4 5}

  • Vomiting: non-bilious, often (but not always) projectile, and usually 30-60 minutes after a feed, with the baby remaining hungry. Projectile vomiting has been described as "vomit which hits the wall across the room" as opposed to "vomit that hits the floor in front of the child".

  • 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. This is present in 60-80% of infants with hypertrophic pyloric stenosis.³

  • The 'olive' is best palpated at the start of a feed but is often missed.⁶

  • 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.

• Feeding problem or milk intolerance.

• Reflusso gastroesofageo.

• Gastroenterite.

• Duodenal atresia, oesophageal atresia or other bowel obstruction in the newborn.

• Intestinal malrotation/acute midgut volvulus.

• 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.⁶

• Ultrasound is reliable and easily performed and is the main investigation.³⁷ There is a normal variation of pylorus muscle measurements with age and gestation but ultrasound has a very high sensitivity and specificity.⁸

• 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 pyloromyotomy.⁹

• 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.¹⁰ An extended pyloromyotomy is required to manage this.

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

• Pyloromyotomy is curative and complications are rare.