There's no question that seeing blood in the toilet bowl, on or in your stool or on the toilet paper is a shock. Bleeding in the colon (large intestine) is not ever normal, and shouldn't be dismissed. Once that initial scare wears off, you will start wondering what is causing the bleeding. If you have some symptoms, the cause of the rectal bleeding might seem obvious, but that doesn't mean you should self-diagnose. Blood in the stool should always be evaluated by a physician. In the meantime, while you're waiting for that doctor appointment, find out more about some of the conditions that could cause visible bleeding from the rectum.
Rectal bleeding due to IBD is more common with ulcerative colitis than it is with Crohn's disease. Bleeding tends to be a hallmark sign of ulcerative colitis because in this form of IBD, the inflammation begins at the end of the colon, in the rectum. Crohn's disease in the colon, particularly in the rectum, could also lead to visible blood on or in the stool. The blood coming from the ulceration in the colon that is associated with these diseases is often fresh, so it tends to be a brighter red in color. In the case of ulcerative colitis, there might be bowel movements that consist mainly of just blood. Blood from higher up in the digestive tract tends to be darker in color and might not be as visible in the stool.
One source of bleeding from the rectum is colon cancer. Colon cancer starts with polyps -- protrusions on the inside wall of the colon. Bleeding from colon polyps might not be visible to the naked eye, and most polyps don't bleed at all. Therefore polyps could be growing in the colon without causing any signs or symptoms at all. Bleeding is a sign of colon cancer, but it might not appear until the cancer is in a more advanced stage. When polyps are removed during a colonoscopy, there is no chance of them developing into cancer.
Diverticular disease is very common; as many as half of all people over age 60 have signs of diverticular disease. Diverticulosis refers to the presence of weak spots on the wall of the large intestine that develop into pockets. These outpouchings are called diverticula (the singular form is diverticulum), and they generally don't produce any symptoms at all. You might not know they were there unless one or more of them get infected, which is then called diverticulitis. Diverticulitis might make a person very sick and cause abdominal pain. In rare cases the diverticula might bleed. The blood could be found in or on the stool, or bleeding could appear without a bowel movement. Diverticular disease could cause quite a bit of bleeding and might or might not need treatment, but it should always be investigated by a physician.
An anal fissure could be a complication of Crohn's disease or childbirth, or the result of hemorrhoids that have ulcerated or straining from severe constipation. This tear in the anal canal could lead to bright red blood in the stool or on the toilet paper, but also to pain during bowel movements. Most fissures are acute, will respond to non-invasive therapies that can be done at home and won't recur. A fissure that becomes chronic and is resistant to heal may need more intensive treatment, such as surgery.
One very common cause of bleeding from the rectum is hemorrhoids. Hemorrhoids are actually veins in the rectum that have swollen. They may cause pain, itching and bright red blood on the stool or on the toilet paper, although many do not cause any symptoms at all. Hemorrhoids are typically not serious and can be treated at home. They should be investigated by a physician in the case of significant bleeding or if they aren't getting any better.
Remember, when there is visible blood in the toilet, coating the stool or on the toilet paper, you should be evaluated medically because of the potential of dangerous blood loss and serious underlying illnesses such as IBD and cancer.