What is the most common cause of a painful gastrointestinal bleed in children?

A painful gastrointestinal bleed in children is most commonly caused by an anal fissure. Anal fissures are small tears in the lining of the anus, which can occur due to passing hard stools or constipation. These fissures can lead to bleeding during bowel movements and often cause significant pain, prompting children to avoid using the bathroom. The pain associated with anal fissures can also result in behavioral changes as children may become reluctant to eat or have bowel movements, further exacerbating the condition.

While other options may contribute to gastrointestinal bleeding in children, they typically do not present with pain as a primary symptom. Meckel's diverticulum can cause complications leading to pain and bleeding, but it is less common than anal fissures. Intussusception, though it can cause severe abdominal pain and bleeding, is more associated with intermittent episodes rather than consistent pain during bowel movements. Hemorrhoids tend to be rare in children, especially when considering painful bleeding as a predominant symptom. Anal fissures, due to their higher incidence and the painful nature of the bleeding they cause, stand out as the most common cause in this context.