Pyloric Stenosis

Basics

Postnatal hypertrophy and hyperplasia of the circular smooth muscle cell layer causing a thickened pylorus and antrum leading to progressive gastric outlet obstruction
Neuronal nitric oxide synthase (NOS-1) may be a genetic susceptibility locus
Administration of erythromycin and azithromycin in infants during first 2 wk of life may increase risk of hypertrophic pyloric stenosis
Jaundice due to transient glucuronyltransferase deficiency
Adult: Caused by peptic ulcer disease

Most common cause of GI obstruction in infants; incidence 1/150 males, 1/750 females (average: 3/1,000 live births)
Males affected 5× more commonly than females; firstborn most common
Familial aggregation noted, 15%:
- Child of affected parent has 7% incidence
- Recurrence risk in subsequent male children is 10%; 2% in females

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