Blood in the stool or visible in tissue after wiping is a common occurrence, according to UpToDate. Most of the time, such blood is caused by conditions, such as anal fissures or hemorrhoids, that are not life threatening. Someone who notices rectal bleeding should consult a physician for an examination to determine the cause.
Hemorrhoids are caused by the inflammation of blood vessels in the anus or rectum, and they often cause pain and bleed, notes UpToDate. The blood from hemorrhoids is commonly bright red and may appear on the stool itself, on the wiping tissue or in the toilet. Hemorrhoids are common and are not typically related to other major health issues. Anal fissures are tears in the lining of the anus, and they also bleed bright red and may be more painful when bleeding during a bowel movement than hemorrhoids.
More serious causes of rectal bleeding include colitis, colon cancer and polyps, reports MedicineNet. If the source of the bleeding is from higher up in the digestive system, the blood is generally darker when it shows up in the stool. Blood from the transverse colon or right colon is often dark red. If the blood originates in the stomach, it is almost black because of its interaction with stomach acids.