About eight months ago I noticed larger and larger amounts of blood in my stool. This continued on and off for about a month. Last week it started up again. What could this be?

--Rosy

Blood in the stool could mean anything from hemorrhoids to Endometriosis to benign colon polyps to colon cancer to trauma from anal sex. Other possibilities include inflammatory bowel disease, such as Crohn's or ulcerative colitis, especially if the bleeding is accompanied by pain and diarrhea. Some parasitic infections may lead to bloody stools as well. Tarry, dark stools may be a sign of bleeding higher in the gastrointestinal tract, such as from an ulcer. Using large amounts of aspirin or nonsteroidal anti-inflammatory drugs (Motrin, Advil, etc.) may also cause blood to appear in the stool. Endometriosis involving the intestinal wall can lead to bloody stools with menstrual periods.

Blood in the stool demands medical evaluation. If the blood appears just on the outside of the stool, it most likely comes from hemorrhoids, but if it persists it should be investigated as well.