What could cause lower back pain and blood in stool?

Maybe related or not: Certain colorectal problems such as ulcerative colitis, proctitis, crohn's disease, cancer, acute diverticulitis can cause lower back pain and blood in stool. But they may not be related--hemrroids, fissures, diverticular bleed, cancer can cause blood in stool and not likely causing back pain. So, without more info it is difficult to tell what you have. Consult doc. Good luck.

Something stinky!: These are 2 common independent issues people seek evaluation. This could be coincidental or the back pain is leading to constipation or vice versa &there is now bleeding from a hemmoroid. This could also be something happening within your GI tract causing both the back pain & blood or even due to taking anti inflammatory medication for your back pain which could be a reason for blood. See md.