What can cause rectal bleeding if the colonoscopies comes back normal?

Colonoscopy: Will look for tumors or polyps in the colon. Most common cause of bleeding may be from hemorrhoids or anal fissure that may not be seen well on colonoscopy. Less common causes of colon bleeding could be vascular malformation or diverticulosis which can bleed intwrmittently & would not be seen at colonoscooy unless there was active bleeding at the time of the procedure.

Hemorrhoids; AVMs: Vascular malformations can sometimes be difficult to see on colonoscopy. These can bleed spontaneously. Most commonly, internal and/or external hemorrhoids, can also be a source of bleeding. Treatment: drink plenty of fluids and a high fiber diet. Also lesions and diseases of the small intestine can be a source of rectal bleeding. Gastric ulcers are usually assoc. With dark black stools.