Intussusception Target Sign CT

A 14-month-old boy presents with 18 hours of intermittent severe colicky abdominal pain, non-bilious vomiting, and a single stool described as dark red jelly-like material. On examination, a sausage-shaped mass is palpable in the right upper quadrant with emptiness in the right lower quadrant (Dance sign). Contrast-enhanced abdominal CT is performed. The structure marked **A** in the diagram—the target or bull's-eye sign with concentric hypodense and hyperdense layers—represents which anatomical relationship?