The figures below are ultrasound scans of a four-month-old child with vomiting and abdominal mass.

Figure 1 shows a transverse section through the thickened pylorus. The echogenic centre represents mucosa and the hypoechoic area represents the muscle.

Figure 2 is a saggital section showing elongation of the pylorus.

Pylorus stenosis is usually apparent on ultrasound and responds to surgery.