But you should talk to your doctor if you notice an increased amount of mucus in stool — particularly if it begins happening regularly or if it's accompanied by bleeding or a change in bowel habits. Larger amounts of mucus in stool, associated with diarrhea, may be caused by certain intestinal infections. Bloody mucus in stool, or mucus accompanied by abdominal pain, can represent more serious conditions — Crohn's disease, ulcerative colitis and even cancer. With. John M. Wilkinson, M.D.