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 then can 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 cancer¹

• Typical presentation is onset of vomiting at 2-8 weeks old but late presentation up to 6 months can occur.² 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: 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'.³
• 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.⁴ 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
• Laparoscopic pyloromyotomy is also performed⁵

• 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 delayed and prolonged severe dehydration occurs
• Mortality is rare after pyloromyotomy⁶