Infantile hypertrophic pyloric stenosis

What it is

In pyloric stenosis there is hypertrophy of the pyloric muscle causing gastric outlet obstruction. It is characterised by hypertrophy and hyperplasia of the pyloric sphincter in the first months of life. Symptoms develop between the 2nd and 7th week of age, irrespective of gestational age, after 3-4 first weeks of normal feeding. The age at which it is seen is also put at 2-20 weeks, with the 2nd to 7th week being the onset of symptoms. It sits in the differential of non-bilious milk vomiting in early life, together with GER and any stenosis down to the first part of the duodenum. Posseting and GER are a non-forceful return of milk or food; vomiting is a forceful ejection of gastric contents. The age is given differently across sources: between the 2nd and 7th week, 2-20 weeks, 3 to 6 weeks of life with presentation very rarely after that, and commonly 6-8 weeks.

Causes and risk

• First baby
• Boys, 4:1 M:F
• Family history, especially maternal
• Exposure to nicotine during pregnancy (smoking mothers)
• Macrolide antibiotics: erythromycin and azithromycin, exposure less than 16 weeks of age
• Bottle feeding