Infant with projectile vomiting AXR AP (left) shows a hugely distended air-filled stomach with distal bowel gas. Sagittal US of a posteriorly positioned pylorus (right) shows the pyloric channel to be lengthened (25 mm) and the pyloric muscle to be thickened (4 mm). The anechoic gallbladder is positioned anteriorly to the pylorus. The diagnosis was hypertrophic pyloric stenosis.