• Classically leads to non-bilious (stenosis occurs above the duodenum) projectile vomiting in a newborn at 2-6 weeks of age that is refractory to dietary changes
• Key idea: In questions asking about management, you want to first correct fluid and electrolyte abnormalities before proceeding with a corrective pyloromyomectomy

Non-bilious vomit in a young boy a few weeks old

• can't be lactose intolerance (switched to soy)
• mustard colored stool

Would also expect

• olive sized abdominal mass
• succession splash on auscultation

Non-bilious ddx

• pyloric stenosis
• TEF

Bilious ddx

• duodenal atresia
• annular pancreas
• malrotation/volvulus
• intestinal atresia