A 5-week-old male infant is brought to the pediatric clinic with complaints of projectile, non-bilious vomiting after every feed for the past 7 days. The parents report that the baby is always hungry after vomiting and feeds vigorously. Physical examination reveals a palpable olive-shaped mass in the right upper quadrant and visible peristaltic waves across the abdomen. An abdominal ultrasound is performed. Which of the following ultrasound findings is most characteristic of infantile hypertrophic pyloric stenosis (IHPS)?
