Intestinal Duplication Cyst

A 6-month-old infant presents with a palpable abdominal mass in the right lower quadrant, intermittent vomiting, and failure to thrive. Abdominal ultrasound shows a well-defined cystic lesion with characteristic "gut signature" (inner hyperechoic mucosal layer and outer hypoechoic muscular layer). Technetium-99m scan demonstrates focal uptake suggesting heterotopic gastric mucosa. At exploratory laparotomy, the structure marked **A** is identified as a spherical cystic duplication attached to the mesenteric border of the distal ileum. The surgeon notes it shares a common muscular wall and common mesenteric blood supply with the adjacent bowel. Given these findings, what is the most appropriate surgical management for the structure marked **A**?