What is the classic presenting symptom and patient age for this condition?
Projectile non-bilious vomiting in infants 1 - 2 months of age.
Ultrasound of the pylorus demonstrates 4mm thick pyloric muscle and increased length of the pyloric canal to 20mm. The thickened muscle forms a prominent hypoechoic target sign on transverse (sagittal with respect to the trunk) imaging . Also note the protrusion of pyloric mucosa in to the antrum.