Your GI tract runs from your mouth to your rectum. Bleeding can occur at any point along the GI tract. The source of blood that appears in the stool is an important indicator of whether the cause may be serious.
Lower GI bleeding
When blood appears fresh, with a bright red color, it most commonly originates in the lower GI tract. This includes the lower part of the small intestine, the colon, the rectum, and the anus. The medical term for this type of blood is hematochezia.
The American College of Gastroenterology (ACG) lists these possible causes of lower GI bleeding:
- Diverticulosis: This is a condition in which small pouches form along the large intestine. The ACG reports that this is the among the most common reasons for lower GI bleeding.
- Angiodysplasias: These are are abnormal blood vessels in the GI tract. The ACG notes that this is the second most common reason for lower GI bleeding.
- Colon polyps: These are small growths that can lead to bleeding. Colon polyps can be benign or cancerous, or they may become cancerous.
- Tumors: Both benign and malignant tumors can cause bleeding if they develop in the large intestine.
- Inflammatory bowel disease (IBD): This includes ulcerative colitis and Crohn’s disease. Inflammation and ulcers that result from these conditions can lead to bleeding.
- Hemorrhoids: These are veins that become swollen near the anus and lower rectum, typically causing blood to appear on toilet paper or in the toilet bowl after a bowel movement.
- Anal fissures: These are small tears that can develop in the anus, and they can result in fresh blood appearing with a bowel movement.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) also mentions rectal prolapse as a cause of blood in the stool. This is when a small section of the rectal wall protrudes outside the anus.
Upper GI bleeding
When blood in the stool appears dark red or black and tarry, the source is typically higher up in the GI tract, including the stomach and small intestine. Melena is the medical term for black, sticky, or tarry stools.
Upper GI bleeding can also appear in vomit as dark blood that looks like coffee grounds.
The NIDDK lists possible causes of upper GI bleeding including:
- peptic ulcers in the stomach
- enlarged veins in the esophagus (esophageal varices) or the stomach (stomach varices)
- tears in the esophagus either from trauma or from prolonged, violent vomiting
- gastritis, or inflammation of the stomach lining
- gastroenteritis, or inflammation of the stomach and intestines
Blood in the stool can be a symptom of colon cancer. However, statistics show this is rare, with cancer present in 3.4% of people who see a doctor for blood in their stool.
Colorectal cancer also often causes other symptoms along with rectal bleeding, including:
- changes in bowel habits, such as going less often or more frequently
- abdominal pain or cramps that do not go away
- diarrhea
- constipation
- feeling that your bowel is not completely empty after a bowel movement
- unexpected weight loss
Early detection is critical in improving treatment outcomes, so talk with your doctor about any symptoms of colorectal cancer, including blood in your stool.
Because some causes of blood in the stool can be serious, talk with your doctor or healthcare professional about any rectal bleeding you experience. They can rule out more complex conditions or begin prompt treatment if necessary.
It is important to tell your doctor about other symptoms you may be experiencing. It also helps to provide details about your bleeding, including how long it has been happening, how much blood you see, and the color and consistency of the blood.
Who to see
In most cases, your family doctor or primary care physician can evaluate your symptoms. They will likely take your vital signs and perform a rectal exam, and they may recommend further testing to rule out certain conditions. Some tests may require you to collect a stool sample.
Your primary care doctor may refer you to a gastroenterologist. Gastroenterologists specialize in conditions and diseases that affect your GI tract. If you have a serious condition that requires surgery, you will receive a referral to a colorectal surgeon. Check with your insurance company to see if you need a referral from your primary doctor before seeing a specialist.
Your treatment options will depend on the cause of your bleeding. Your doctor will discuss your individual diagnosis and advise on the next steps for treatment.
Learn how to treat hemorrhoids at home and when to see a doctor.
In some cases, blood in the stool could be a symptom of cancer that is causing a bowel obstruction. Seek immediate medical help or call 911 if you have blood in the stool along with symptoms including:
- abdominal cramps
- bloating
- constipation
- vomiting
Black tarry stools accompanied by lightheadedness or feeling faint may indicate a serious upper GI bleed that requires emergency treatment.
Blood in the stool can be an alarming symptom, and it is important to contact your healthcare professional for an accurate diagnosis.
The color and consistency of the blood can indicate the source of the bleeding along the GI tract. Fresh, bright red blood often comes from the lower GI tract. Bleeding from the upper GI tract can appear as dark red or black and tarry.
Common causes of blood in the stool include diverticulitis, IBD, hemorrhoids, and anal fissures.
It is rare for blood in the stool to be a symptom of colon cancer. However, because early detection is critical for treating this type of cancer, it is important to talk with a doctor or another healthcare professional about any bleeding in the stool.
