In a 2-year-old with painless rectal bleeding, which condition is most likely?

In a 2-year-old presenting with painless rectal bleeding, Meckel diverticulum is the most likely condition. This is a congenital pouch that can form on the small intestine, representing a remnant of the omphalomesenteric duct. It is quite common and can be present from birth without causing symptoms until later in life.

The bleeding associated with Meckel diverticulum usually occurs due to the presence of heterotopic gastric mucosa, which can become ulcerated and lead to painless rectal bleeding. This presentation is particularly notable in children, as they may not exhibit pain, which can help distinguish it from other causes of rectal bleeding.

In contrast to Meckel diverticulum, hemorrhoids, although possible, are less common in such young children, especially when they do not exhibit any signs of pain. Anal fissures typically present with painful bleeding, often associated with difficult bowel movements, and are not usually characterized by painless rectal bleeding. Intussusception, on the other hand, is usually accompanied by abdominal pain and may present with "currant jelly" stools, indicating a more emergent situation, making it less likely in this scenario of painless bleeding.