Hello, Thanks for your query. There are many possible causes. Below is a brief overview of the more common causes: Haemorrhoids (piles) Anal fissure Diverticula Polyps Angiodysplasia Various abnormalities of the gut, or the gut wall may cause rectal bleeding in young children. An ulcer in the stomach or duodenum may bleed. This can cause melaena - where your faeces turn black as described earlier. May cause bloody diarrhoea due to inflammation of the gut, caused by some infections. I do hope that you have found something helpful and I will be glad to answer any further query. Take care