My kid (her account) is under 16 and has rectal bleeding for less than a year but a while. it's only when she goes to the bathroom. condition/cause?

Rectal bleeding: I would first consider softening the stools. Constipation and large, hard bowel movements can often be the cause of bleeding. There could also be other causes like hemmhoroids or fissures, among others. Appropriate use of fiber supplements to soften the stools can be helpful. If this doesn't work, i recommend consulting with your doctor.