Hello and welcome to HCM, Injury to the tail bone in the form of fracture or injury to surrounding soft tissues is unlikely to cause a bloody diarrhea. Bloody diarrhea is caused due to infection in the gastrointestinal tract, inflammatory bowel disease, mesenteric vein occlusion or injury to anal canal mucosa etc. A stool examination will help to determine the cause of bloody diarrhea. In case there is presence of infectious agent, it will be detected on stool examination. In case there is no evidence of infectious agent in the stool, examination of the lower gastrointestinal tract will be required to look for probable cause of bleeding. However, injury to tail bone is not the likely cause of bloody diarrhea. Thanks and take care Dr Shailja Puri