Why Are There Blood Clots in Your Stool?

Medically reviewed by Jay N. Yepuri, MD

Blood clots in your stool are a sign of bleeding in the gastrointestinal tract. There are many possible causes for the bleeding, ranging from minor conditions like anal fissures and hemorrhoids to more serious conditions like colon cancer and ulcerative colitis.

It can be unsettling to find blood clots in your stool. Whether you notice them occasionally or consistently, it is important to see a healthcare provider to determine the cause and get any necessary treatment.

What Are Blood Clots?

Blood clots are semi-solid, gel-like masses formed when cells, platelets (tiny blood cells that help with blood clotting), and proteins clump together. Blood clots help prevent excessive bleeding when you're cut or injured. When blood clots are in the stool, it's a sign of bleeding somewhere in your gastrointestinal (GI) tract.

Specifically, a blood clot in the stool means the blood that's being lost in your GI tract had time to coagulate (change from a liquid to a semi-solid state) and form a clump. Not all GI bleeds turn into a blood clot. If the blood in your GI tract doesn't have time to go through the coagulation process, the blood would be more liquid-y, Kumkum Sarkar Patel, MD, a gastroenterologist in California and a member of Health's Medical Expert Board, told Health.

Besides how quickly the bleed is occurring, the medication you take can also influence whether the bleed will form a blood clot, according to Dr. Patel. For instance, blood thinners can slow down the coagulation process, meaning people on blood thinners are less likely to have blood clots—especially if the bleeding is severe.

What Does a Blood Clot in the Stool Look Like?

When in your GI tract, the blood clot can mix within the stool or adhere to the outside of your stool, Dr. Patel said. That means when your stool and clot make their way out of your body, you can see the gel-like clump of blood either mixed in to your stool or attached to the outside.

The clot can vary in size, Dr. Patel added, ranging anywhere from the size of a dime to the size of a silver dollar.

The blood clot's color can also vary, often providing a clue about whether the bleed is occurring in the upper or lower GI tract. The higher up in the GI tract the bleed, the darker the blood clot. This is because the blood has had more time in the tract to react with oxygen and, in turn, become darker.

Possible Causes of Blood Clots in Stool

Several conditions can cause blood clots in stool. Some conditions are minor and heal with time and treatment. Other conditions are more serious and may require long-term or lifelong treatment. You may have blood clots in your stool due to the following conditions:

Hemorrhoids

Hemorrhoids are swollen, inflamed veins in the lower rectum and anus. Straining during bowel movements, having chronic constipation, or frequently lifting heavy objects can lead to hemorrhoids. hemorrhoids can cause pain, anal itching, and anal bleeding. The blood might appear as a clot if the hemorrhoid has burst, according to Dr. Patel.

Anal Fissures

An anal fissure is a small tear in the lining of the anus. Straining during bowel movements; passing large, hard stools; or having prolonged diarrhea can lead to anal fissures. Anal fissures cause sharp pain during and after bowel movements, rectal bleeding, and bright red blood clots.

Diverticular Disease

Diverticular disease is also known as diverticulosis. This is a condition in which small pouches, called diverticula, develop in the colon's wall. Many people with these pouches do not develop symptoms. However, if one of the pouches becomes infected or inflamed, blood vessels within the diverticula can burst and cause significant bleeding and blood clots that may appear bright or dark red.

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) describes a group of conditions that affect the digestive tract. The two main types of IBD are Crohn's disease and ulcerative colitis. With IBD, inflammation can damage the lining of the digestive tract, causing inflammation and ulcers that bleed. IBD-related blood clots in the stool may be bright red if the bleeding is occurring in the large intestine or rectum. Darker red or black blood clots are usually from bleeding higher up in the digestive tract, such as the small intestine.

Gastroenteritis

Gastroenteritis is an intestinal infection caused by viruses or bacteria, such as norovirus, rotavirus, E. coli, or Salmonella. Gastroenteritis typically causes diarrhea, vomiting, abdominal pain, and fever. Severe gastroenteritis can lead to bloody diarrhea and dark red or tarry blood clots that may contain mucus.

Ischemic Colitis

Ischemic colitis is when the colon is damaged or injured due to impaired or blocked blood flow. It is most common among older adults and people with heart and blood vessel diseases. Symptoms include abdominal pain (typically on the left side); frequent, bloody diarrhea containing dark red blood clots; and sometimes bright red bleeding from the rectum without passing stool.

Peptic Ulcer Disease

Peptic ulcers are open sores in the stomach lining or duodenum (the upper part of the small intestine). Peptic ulcer disease develops due to a bacterial infection (H. pylori bacteria) or long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as Bayer (aspirin) or Advil (ibuprofen). Peptic ulcers can cause internal bleeding that ranges from minor to life-threatening in severity. Blood clots in stool from a peptic ulcer appear dark, tarry, or maroon.

Colon Cancer

Colon cancer develops when small growths (polyps) in the colon or rectum are not removed and become cancerous. Early colon cancer often causes no symptoms, but as the tumor grows, the cancer invades the intestinal wall or rectum, causing blood vessels to burst and bleed. Blood clots in stool due to colon cancer may be bright or dark red and mixed with mucus, depending on the tumor's location.

Are Blood Clots in Stool Serious?

It is important to see a healthcare provider if you notice blood clots in your stool. While not all possible causes are serious or life-threatening, most causes require treatment and management to prevent complications.

Some causes of blood clots in stool, such as a severe peptic ulcer, can lead to rapid blood loss and require immediate treatment. Seek prompt medical attention if you experience any of the following symptoms along with blood clots in your stool:

• Severe abdominal pain

• Fever

• Dizziness or fainting

• Difficulty breathing or shortness of breath

• Sudden, severe diarrhea

• Nausea and vomiting

• Rapid heart rate 
  

Diagnosis

To diagnose the cause of blood clots in stool, your healthcare provider may ask about other symptoms you are experiencing, review your medical history, and perform a physical examination. They might order diagnostic tests to identify the location and cause of bleeding, which could include:

• Stool tests: You will provide a stool sample, which is sent to the lab to check for the presence of blood, bacteria, viruses, and parasites.

• Blood tests: Blood samples are taken through a vein and checked for anemia, infection, and inflammation markers.

• Colonoscopy: In this procedure, a thin, flexible tube equipped with a camera is inserted into the anus to view the rectum and colon to look for bleeding and other abnormalities, such as inflammation, polyps, or tumors.

• Sigmoidoscopy: Similar to a colonoscopy, this procedure involves inserting a thin, flexible tube with a camera into the anus to examine the rectum and the lower portion of the colon to check for bleeding, polyps, and other abnormalities.

• Abdominal computed tomography (CT) scan: This imaging test combines X-ray pictures to create 3D images of your gastrointestinal tract to look for the source and cause of bleeding.

Treatment

The treatment for blood clots in stool depends on the underlying cause. The goal of treatment is to manage the underlying condition, though heavy GI bleeding may require certain types of procedures to stop the source of bleeding.

Possible treatments for blood clots in stool include:

• Hemorrhoids: Eating high-fiber foods, staying hydrated, and avoiding straining during bowel movements may help treat mild hemorrhoids. Over-the-counter medications such as pain relievers and stool softeners may help relieve hemorrhoid symptoms. Healthcare providers may also have to perform minimally invasive procedures to shrink or close off hemorrhoids. Surgery may be necessary in severe cases.

• Anal fissures: A high-fiber diet and over-the-counter stool softeners may help make bowel movements easier. Sitz baths (a warm, shallow bath you sit in, particularly after a bowel movement) and topical over-the-counter lidocaine medications may help relieve anal pain. Severe, chronic anal fissures may require Botox (botulinum toxin) injections to help relax the anal sphincter muscles and promote healing.

• Diverticular disease: Depending on the severity of the bleeding, treatment may include blood transfusions to replace blood loss, antibiotics, or medicines for pain relief. Electrocauterization (the process of heating tissue with electricity) to stop the bleeding or surgery to drain an abscess may be necessary.

• Inflammatory bowel disease: Common IBD treatments include dietary changes to avoid IBD triggers and anti-inflammatory and immunosuppressant prescription medications to control inflammation and promote GI tract healing.

• Gastroenteritis: Treatment depends on the severity and cause of gastroenteritis. This may include antibiotics or antiparasitic medicines to clear an infection. Probiotics may help support gastrointestinal health to help slow or stop diarrhea.

• Ischemic colitis: Treatment may include intravenous (IV) fluids, pain relievers, and antibiotics. Surgery to improve blood flow to the colon and repair damaged tissue may be necessary in severe cases.

• Peptic ulcer disease: Treatment may include antibiotics to eliminate H. pylori bacteria. Proton pump inhibitors (PPIs) and H2 blockers help reduce stomach acid production to promote healing.

• Colon cancer: Treatment may include chemotherapy, immunotherapy, or radiation therapy to kill cancer cells or surgery to remove the tumor.

A Quick Review

Blood clots in stool indicate bleeding in the gastrointestinal tract. The bleed happens slow or high enough in the GI tract that the blood has time to change into a gel-like substance and clump together. There are many possible causes of blood clots in your stool, from temporary conditions like anal fissures and hemorrhoids to chronic conditions like inflammatory bowel disease and diverticular disease. The blood clots can be different colors based on where in the gastrointestinal tract the bleed is happening. Talk to your healthcare provider if you notice blood clots in your stool. The provider may order diagnostic tests, such as stool tests, blood tests, imaging tests, or a colonoscopy to determine the cause. Treatment options vary depending on the cause of the bleeding and may include lifestyle modifications, medications, or surgery. 

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