Hypertrophic pyloric stenosis - classically presents as non-bilious projectile vomiting during the second month of life. Ultrasound is excellent for first line assessment with the pylorus considered hypertrophied if it exceeds 15mm in length and 3mm or more in thickness (from lumen to outer edge). The stomach will usually be distended with fluid and at no time during the scan will the pylorus open.
Pyloric Stenosis: Ultrasound of the abdomen shows a longitudinal section of the pylorus with increased muscle thickness (measuring 4 mm between the calipers labeled “2″) and increased length of the pyloric channel (measuring about 22 mm between the calipers labeled “1″).
SonoSite- Helpful Ultrasound tutorials. Used as pre-class material in our Ultrasound Elective.