Blood in the stool can be concerning, whether you discover it while wiping after a bowel movement or from a test ordered by your doctor.
While blood in stool can signal a serious problem, it doesn't always. Here's what you need to know about the possible causes of bloody stools and what you -- and your doctor -- should do if you discover a problem.
Causes of Blood in Stool
Blood in the stool means there is bleeding somewhere in your digestive tract. Sometimes the amount of blood is so small that it can only be detected by a fecal occult test (which checks for hidden blood in the stool). At other times it may be visible on toilet tissue or in the toilet after a bowel movement as bright red blood. Bleeding that happens higher up in the digestive tract may make stool appear black and tarry.
Possible causes of blood in the stool include:
Inflammatory bowel disease (IBD). If you have bloody diarrhea and pain that goes on for weeks, along with weight loss, IBD might be the reason. This long-term condition inflames parts of your digestive tract. Experts aren’t sure exactly why that happens. There are two main kinds of IBD: ulcerative colitis and Crohn’s disease.
Ischemic colitis. This is when blood flow to your colon slows down or stops. The lack of oxygen causes damage to your intestine. The blockage can happen slowly over time, such as when cholesterol builds up in your arteries. Or it can happen all of a sudden from a blood clot or from a serious drop in your blood pressure. It can lead to bloody diarrhea. It usually also comes with abdominal pain that can be serious. The pain usually worsens when you eat.
Bacterial infections. Bloody diarrhea from IBD can last for a while if you don’t treat it. If it’s from a bacterial infection, it doesn’t usually last more than 2 weeks. It doesn’t come back after it gets better unless you catch the same infection again. Bacterial infections that can cause bloody diarrhea include E. coli., salmonella, shigella, and campylobacter.
Diverticular disease. Diverticula are small pouches that project from the colon wall. Usually diverticula don't cause problems, but sometimes they can bleed or become infected.
Anal fissure. This is a small cut or tear in the tissue lining the anus similar to the cracks that occur in chapped lips or a paper cut. Fissures are often caused by passing a large, hard stool and can be painful.
Colitis. This is inflammation of the colon.
Angiodysplasia. This is a condition in which fragile, abnormal blood vessels lead to bleeding.
Peptic ulcer. This is an open sore in the lining of the stomach or duodenum, the upper end of the small intestine. Many peptic ulcers are caused by infection with a bacterium called Helicobacter pylori (H. pylori). Long-term use or high doses of anti-inflammatory drugs such as aspirin, ibuprofen, and naproxen can also cause ulcers.
Polyps or cancer. Polyps are benign growths that can grow, bleed, and could become cancerous. Colorectal cancer is the fourth most common cancer in the U.S. It often causes bleeding that is not noticeable with the naked eye.
Esophageal problems. Varicose veins of the esophagus or tears in the esophagus can lead to severe blood loss.
Blood in Stool Diagnosis
It is important to have a doctor evaluate any bleeding in the stool. Any details you can give about the bleeding will help your doctor locate the site of bleeding. For example, a black, tarry stool is likely an ulcer or other problem in the upper part of the digestive tract. Bright red blood or maroon-colored stools usually indicate a problem in the lower part of the digestive tract such as hemorrhoids or diverticulitis.
After getting a medical history and doing a physical exam, your doctor may order tests to determine the cause of bleeding. Tests may include:
Nasogastric lavage. This test might tell your doctor whether bleeding is in the upper or lower digestive tract. The procedure involves removing the contents of the stomach through a tube inserted into the stomach through the nose. If the stomach does not contain evidence of blood, the bleeding may have stopped or is more likely in the lower digestive tract.
Esophagogastroduodenoscopy (EGD). This is a procedure that involves inserting an endoscope, or flexible tube with a small camera on the end, through the mouth and down the esophagus to the stomach and duodenum. The doctor can use this to look for the source of bleeding. Endoscopy can also be used to collect small tissue samples (called a biopsy) for examination under a microscope.
Colonoscopy. This is similar to an EGD except the scope is inserted through the rectum to view the colon. As with an EGD, colonoscopy can be used to collect tissue samples to biopsy.
Enteroscopy. A procedure similar to EGD and colonoscopy used to examine the small intestine. In some cases this involves swallowing a capsule with a tiny camera inside that transmits images to a video monitor as it passes through the digestive tract.
Barium X-ray. This procedure uses a contrast material called barium to make the digestive tract show up on an X-ray. The barium may either be swallowed or inserted into the rectum.
Radionuclide scanning. This procedure involves injecting small amounts of radioactive material into a vein and then using a special camera to see images of blood flow in the digestive tract to detect where bleeding is happening.
Angiography. A special dye is injected into a vein to make blood vessels visible on an X-ray or CT scan. The procedure detects bleeding as dye leaks out of blood vessels at the bleeding site.
Laparotomy. This is a surgical procedure in which the doctor opens and examines the abdomen. This may be necessary if other tests fail to find the cause of bleeding.
Health care providers also order lab tests when there is blood in stools. These tests may look for clotting problems, anemia, and H. pylori infection.
A person with blood in the stool may be unaware of bleeding and might have reported no symptoms. On the other hand, they may also have abdominal pain, vomiting, weakness, difficulty breathing, diarrhea, palpitations, fainting, and weight loss depending on the cause, location, length, and severity of the bleeding.
Blood in Stool Treatments
A doctor can use one of several techniques to stop acute bleeding. Often, endoscopy is used to inject chemicals into the site of bleeding, treat the bleeding site with an electric current or laser, or apply a band or clip to close the bleeding vessel. If endoscopy does not control bleeding, the doctor may use angiography to inject medicine into the blood vessels to control bleeding.
Beyond stopping the immediate bleeding, if necessary, treatment involves addressing the cause of bleeding to keep it from returning. Treatment varies depending on the cause and may include medications such as antibiotics to treat H. pylori, ones to suppress acid in the stomach, or anti-inflammatory drugs to treat colitis. Surgery may be needed to remove polyps or the parts of the colon damaged by cancer, diverticulitis, or inflammatory bowel disease.
Depending on the cause, however, treatment may involve simple things you can do on your own. These include eating a high-fiber diet to relieve constipation that can cause and aggravate hemorrhoids and anal fissures, and taking a sitz bath, which means sitting in warm water to relieve fissures and hemorrhoids.
Your doctor will prescribe or recommend treatment based on the diagnosis.