A 6 year old male presents with report of bloody stool, but…

A 6 year old male presents with report of bloody stool, but no history of diarrhea or constipation.  A stool guaiac is obtained and is positive.  On exam the patient’s abdomen is mildly tender and non-distended.   The mother reports that this has occurred once in the past and a CT scan at that time was negative.  Based on the child’s age and symptoms you would suspect: