Meckel diverticulum

A 20-month-old boy comes to the emergency department because of rectal bleeding and abdominal pain. The mother says that 3 days ago, he first had a small episode of rectal bleeding but that he did not show any signs of irritation or pain and that he was acting normal throughout the day. However, today he was found gripping his abdomen and crying in pain. Abdominal examination shows generalized tenderness to palpation. An abdominal X-ray shows a gasless abdomen and mild intestinal dilatation. Which of the following condition does the patient most likely have?