Hypertrophic Pyloric Stenosis

Synonyms: congenital hypertrophic pyloric stenosis, infantile hypertrophic pyloric stenosis

Diffuse hypertrophy and hyperplasia of the smooth muscle of the antrum of the stomach and pylorus, usually occurring in infants 2-8 weeks of age. The pyloric muscle hypertrophy results in narrowing of the pyloric canal, which can then become easily obstructed.

• Occurs in 1 in 500 live births.
• More common in males than in females, with reported ratios ranging from 2:1 to 5:1.
• First-born male children are believed to have the highest risk.
• Hypertrophic pyloric stenosis occurs very rarely in adults and must then be differentiated from gastric cancer.^1,2

• Typical presentation is onset of vomiting at 2-8 weeks old but late presentation up to 6 months can occur.³ 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, infrequent or absent bowel movements.
• Look for signs and degree of dehydration.
• Stomach wall peristalsis may be visible.
• An enlarged pylorus, classically described as an "olive", can usually be palpated in the right upper quadrant or epigastrium of the abdomen:
  • 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
• Gastro-oesophageal reflux
• Gastroenteritis
• Duodenal atresia, oesophageal atresia or other bowel obstruction in the newborn
• Intestinal malrotation
• Acute midgut volvulus

• Serum electrolytes for correction of electrolyte imbalances before surgical repair: there is often metabolic alkalosis with severe potassium depletion.
• Ultrasound is reliable and easily performed and has become the main investigation. Imaging is not required if an experienced examiner is able to palpate an 'olive'.⁴
• Although ultrasound is most often performed, one study found upper gastrointestinal barium series to be more cost-effective than ultrasound because fewer secondary studies were required.⁵
• A further advantage of a barium study is that it can identify other possible diagnoses such as gastro-oesophageal reflux.

• Preoperative management is directed at correcting the fluid deficiency and electrolyte imbalance.
• Ramstedt pyloromyotomy is easily performed and is associated with minimal complications.⁶
• Laparoscopic pyloromyotomy is also performed and is an effective alternative.⁷

• Vomiting can lead to dehydration, weight loss, and severe electrolyte disturbance with hypokalaemic, hypochloraemic metabolic alkalosis.
• Operative complications include mucosal perforation, continued postoperative bleeding (very rare), and persistent vomiting due to incomplete pyloromyotomy (rare).

• Prognosis is excellent unless diagnosis is delayed and prolonged severe dehydration occurs.
• Mortality is rare after pyloromyotomy.⁸