Hi. Thanks for your query. Noted the history of fall on a bum very hard, there is agonizing pain in the left buttock an thigh, noticed blood in stool, wants to know whether to worry about... If the blood in stool is for the first time and that too after such an injury, this is a big concern. I would advise you the following in such a situation. Consult your General Surgeon asap for clinical evaluation, examination, per-rectal examination, proctoscopy and colonoscopy. CT scan of the whole are to see for any hematoma, collection in any area and fractures of the involved area bones must be done. This gives the proper diagnosis so that further management can be done properly. Stop taking anything orally till advised so. Get admitted. Take strict bed rest till the investigations are conducted.