Bleeding in the Digestive Tract: Why It Happens

Medically Reviewed by Minesh Khatri, MD on March 17, 2024
6 min read

Bleeding in the digestive tract is a symptom of a problem rather than a disease itself. It usually happens due to conditions that can be cured or controlled, such as hemorrhoids.

The cause of the bleeding may not be serious, but it's important for your doctor to find the source of this symptom. The digestive or gastrointestinal (GI) tract includes the esophagus, stomach, small intestine, colon, rectum, and anus. Bleeding can come from one or more of these areas -- from a small area such as an ulcer on the lining of the stomach or from a broader problem such as inflammation of the colon.

You may not know if it happens. Doctors call this type of bleeding “occult” or “hidden.” Fortunately, simple tests can check for hidden blood in the stool.

The reasons vary, depending on where the bleeding is happening.

If it’s in your esophagus (the tube that connects your mouth to your stomach) causes can include:

Esophagitis and gastroesophageal reflux. Stomach acid that returns, or "refluxes," back into the esophagus from the stomach can cause irritation and inflammation of the esophagus (esophagitis) that may lead to bleeding. Read more about gastroesophageal reflux (GERD).

Varices. These are abnormally enlarged veins usually located at the lower end of the esophagus or the upper stomach. They may break open and bleed. Cirrhosis of the liver is the most common cause of esophageal varices. Learn more about the symptoms of bleeding varices.

Mallory-Weiss tear. This is a tear in the lining of the esophagus. It’s usually caused by severe vomiting. It can also happen due to things that increase pressure in your belly, such as coughing, hiccupping, or childbirth. Find out more on nausea and vomiting.

Bleeding from the stomach can be caused by:

Gastritis. This is inflammation in the stomach. Alcohol and some pain medicines can cause it.

Ulcers. Ones in the stomach may enlarge and erode through a blood vessel, causing bleeding. Aside from medication, the most common cause of these is an infection with a bacterium called Helicobacter pylori. Also, people who have had burns, shock, head injuries, or cancer, and those who've had major surgery, may get stress-related stomach ulcers. Get the facts on peptic ulcers.

Intestinal ulcers are usually caused by excess stomach acid and infection with Helicobacter pylori.

Cancer of the stomach.

Bleeding from the lower digestive tract (colon, rectum, and anus) can be caused by:

Hemorrhoids. These are probably the most common cause of visible blood in the lower digestive tract, especially blood that appears bright red. Hemorrhoids are enlarged veins in the anal area that can rupture and produce blood, which can show up in the toilet or on toilet paper. Learn about the symptoms and causes of hemorrhoids.

Anal fissures. Tears in the lining of the anus can also cause bleeding. These are often very painful. Find out how to treat anal fissures.

Colon polyps. These are growths that can happen in the colon. Some can turn into cancer over time. Colorectal cancer can also cause bleeding. Read more on what you should know about colon polyps.

Intestinal infections. Inflammation and bloody diarrhea can result from intestinal infections. Learn more about common infections such as H. pylori.

Ulcerative colitis. Inflammation and extensive surface bleeding from tiny ulcerations can be the reason for blood showing up in the stool. Get an overview of ulcerative colitis (UC).

Crohn's disease is an immune system condition. It causes inflammation and can result in rectal bleeding. Know the difference between UC and Crohn's disease.

Diverticular disease is caused by diverticula -- little “pouches” that bump out from the colon wall. Read about the symptoms of diverticular disease.

Blood vessel problems. As you age, issues may crop up in the blood vessels of the large intestine, which may cause bleeding. It’s not a normal part of getting older, but it is more likely later in life.

Ischemic colitis. This means that not enough oxygen is getting to the cells that line the intestine. Bloody diarrhea, often accompanied by belly pain, can happen if not enough blood gets to the intestine, which results in ischemia, or insufficient blood supply, and damage to cells lining the intestine. Get the facts on ischemic colitis.

These include:

  • Bright red blood coating the stool
  • Dark blood mixed with the stool
  • Black or tarry stool
  • Bright red blood in vomit
  • "Coffee-grounds" appearance of vomit

Other signs, which also need a doctor’s attention, include:

  • Fatigue, weakness, pale appearance
  • Anemia -- your blood is low on iron-rich hemoglobin

The location of the bleeding may affect what you notice.

If it comes from the rectum or the lower colon, bright red blood will coat or mix with your stool. The stool may be mixed with darker blood if the bleeding is higher up in the colon or at the far end of the small intestine.

When there's bleeding in the esophagus, stomach, or duodenum (part of the small intestine), the stool is usually black, tarry, and very foul-smelling. Vomit may be bright red or have a "coffee-grounds" appearance when bleeding is from the esophagus, stomach, or duodenum.

If bleeding is hidden, you might not notice any changes in stool color.

Keep in mind that some medications, such as iron, bismuth, and the antibiotic cefdinir, and some foods, such as beets, can give the stool a red or black appearance that looks like blood but isn't.

Symptoms also vary depending on how quickly you bleed.

If sudden, massive bleeding happens, you may feel weak, dizzy, faint, short of breath, or have cramp-like belly pain or diarrhea. You could go into shock, with a rapid pulse and drop in blood pressure. You may become pale.

If bleeding is slow and happens over a long time, you may gradually feel fatigue, lethargy, and shortness of breath. Anemia can happen, making your skin look more pale.

If you notice any unusual bleeding, make an appointment to see your doctor. They'll ask you questions and give you a physical examination. Symptoms such as changes in bowel habits, stool color (black or red), consistency, and whether you have pain or tenderness may tell your doctor which area of the GI tract is affected.

They'll test your stool for blood. You'll also take a blood test to check to see if you're anemic. The results will give your doctor an idea of the extent of the bleeding and how chronic it may be.

If you have bleeding in your digestive tract, you'll likely get an endoscopy. This common procedure lets your doctor see exactly where the symptom is happening. In many cases, the doctor can use the endoscope to treat the cause of bleeding, too. It's a thin, flexible tool that they can insert through your mouth or rectum to see the areas of concern and take a tissue sample, or biopsy, if needed.

Several other procedures can be used to find the source of bleeding, including:

X-rays. During these tests you either drink or have barium-containing fluid placed through your rectum. Then an X-ray is used to look for any unusual signs. Barium lights up on this imaging test.

Angiography. Doctors inject a dye into a vein before you get a CT scan or MRI. The dye helps to show where the trouble is. In some cases, doctors use angiography to inject medicine that may stop the bleeding.

Radionuclide scanning. Doctors can use this screening technique to find sites of bleeding, especially in the lower digestive tract. You’ll get a shot of a small amount of harmless radioactive material before your doctor uses a special camera to take pictures of your organs.

Most cases can be treated. Your plan will depend on what’s causing the bleeding.

You may get an endoscopy. For instance, if your upper digestive tract is bleeding, your doctor may be able to control it by injecting a medication directly into the problem area, using an endoscope to guide the needle. A doctor can also use heat to treat (or “cauterize”) an area that’s bleeding and surrounding tissue through the endoscope, or place a clip on a bleeding blood vessel.

Those techniques aren’t always enough. Sometimes you need surgery.

Once the bleeding is under control, you may need to take medicine to keep it from coming back.