Is blood in stool always obvious? I have normal bowel movements but every so often I see a dark patch or two on the stool. I would describe it as reddish/brown or rust. But it's hard to tell. Also have been having left lower abdominal discomfort for almost 6 months now! Had an ultrasound done and pelvic scan but nothing found. A few medical professionals I've spoken to think it's muscular but I just want to be sure.