The main reasons for visible mucus in the stool include digestive issues such as ulcerative colitis, anal fissures and irritable bowel syndrome, according to About.com. Bowel obstruction and Crohn's disease may also cause visible mucus in the stool.
Mucus is found in all stool, but normal stool only has a small amount, states About.com. The mucus that appears in the stool is from the large intestine where it protects the lining and helps stool pass through. Mucus in the stool is not harmful, but it could indicate an underlying condition that requires medical treatment. A person should see a doctor if mucus is often found in the stool, but only if not diagnosed with a condition known for mucus in the stool.
Another reason a person may notice mucus in the stool is due to a bacterial infection or bowel obstruction, claims About.com. Some bacterial infections known to cause mucus in the stool include salmonella and campylobacter. If the mucus is caused by a bacterial infection, the individual also may experience fever, diarrhea and abdominal pain. If the mucus is caused by a bowel obstruction, the person may also experience cramping, constipation, vomiting and abdominal distention. An obstruction may be caused by impacted stool, gallstones, a tumor or hernia.