Why did jess of terabithia want a gut transplant?

In the book "Bridge to Terabithia" by Katherine Paterson, the character Jess does not want a "gut transplant." Jess is a young boy who forms a strong friendship with a girl named Leslie, and together they create an imaginary kingdom called Terabithia to escape from their real-world problems. The story focuses on themes of friendship, imagination, and dealing with loss.