This 4-week-old male infant presented with projectile nonbilious emesis and failure to thrive. Panel A is a supine radiograph and Panel B a left lateral decubitus radiograph of the abdomen, revealing a dilated air-filled stomach (asterisk) with a lobulated appearance compatible with peristalsis (arrows) and a single air-fluid level (arrowhead). These are nonspecific signs but suggest a gastric outlet obstruction. Further evaluation with ultrasound identified hypertrophic pyloric stenosis.
