Why Do You Have Blood In Your Stool? Causes

Finding blood in your stool is alarming, and it is one of the most common reasons people see a gastroenterologist. The causes range from harmless conditions like a small tear in the skin around the anus to serious problems like colon cancer. Because the cause cannot be determined by how you feel, any visible blood in your stool should be evaluated by a doctor.

What Does the Color of the Blood Tell You?

The color of the blood gives the first clue about where the bleeding is happening. This is not a diagnosis, but it helps your doctor know where to look.

Bright red blood usually means the bleeding is low in the digestive tract. This includes the rectum, the anus, or the lower part of the colon. When blood is fresh and close to the exit, it stays red.

Dark red or maroon blood often means the bleeding is higher up in the colon. The blood has had time to partially digest, which changes its color.

Black, tarry stools — a condition called melena — point to bleeding in the upper digestive tract. This includes the stomach or the first part of the small intestine. Stomach acid turns the blood black.

Blood that is not visible to the eye is called occult blood. It is only found through a stool test. This type of bleeding can come from anywhere in the digestive tract.

Why Do You Have Blood In Your Stool? Common Causes

Several conditions can cause blood in the stool. Some are minor and resolve on their own. Others require ongoing treatment. A few are life-threatening.

Hemorrhoids are the most common cause of bright red blood in the stool. These are swollen veins in the lower rectum or anus. They can bleed during a bowel movement, leaving streaks of blood on the toilet paper or in the toilet bowl. Straining, pregnancy, and chronic constipation increase the risk of developing hemorrhoids.

Anal fissures are small tears in the lining of the anus. They usually happen when a hard stool stretches the tissue too much. The bleeding is typically bright red and small in amount. Anal fissures cause sharp pain during and after a bowel movement.

Diverticular disease is another common source of bleeding. Diverticula are small pouches that can form in the wall of the colon. When these pouches bleed, the blood can be heavy and sudden. This condition becomes more common with age.

Inflammatory bowel disease (IBD) — which includes ulcerative colitis and Crohn’s disease — causes inflammation in the digestive tract. This inflammation can lead to ulcers that bleed. Blood with mucus in the stool is a common sign of active IBD.

Colon polyps are growths on the inner lining of the colon. Most polyps do not cause symptoms, but larger ones can bleed. Some types of polyps can become cancerous over time, which is why colonoscopy screening is important.

Colorectal cancer is a serious cause of blood in the stool. The bleeding may be small and intermittent at first. It can be bright red, dark red, or black depending on where the cancer is located. Other warning signs include changes in bowel habits, unexplained weight loss, and feeling that the bowel does not empty completely.

Less Common Causes of Rectal Bleeding

Some causes of blood in the stool are less common but still important to know about.

Angiodysplasia is a condition where abnormal blood vessels form in the colon. These vessels are fragile and can bleed without warning. The bleeding may stop on its own, but it can also be severe and recur.

Infections from bacteria such as Salmonella, Shigella, or E. coli can cause inflammation in the colon that leads to bleeding. These infections usually also cause diarrhea, fever, and abdominal cramps.

Ischemic colitis happens when blood flow to the colon is reduced. This can cause tissue damage and bleeding. It is more common in older adults and people with narrowed arteries.

Peptic ulcers in the stomach or duodenum can bleed heavily. The blood travels through the digestive tract and comes out as black, tarry stool. Long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen increases the risk of ulcers.

When Is Blood in the Stool an Emergency?

Some situations require immediate medical attention. Do not wait to see if the bleeding stops on its own.

Seek emergency care if you have blood in the stool along with any of these signs:

• Dizziness or fainting
• Rapid or weak pulse
• Severe abdominal pain
• Large amounts of blood
• Blood mixed throughout the stool rather than on the surface
• Black, tarry stools along with vomiting blood

Heavy bleeding can cause a dangerous drop in blood pressure. This is a medical emergency. The body can lose a significant amount of blood through the digestive tract before you feel weak, so do not delay seeking care.

How Doctors Find the Cause

A doctor will start with a physical exam and a discussion of your symptoms. They will ask about the color of the blood, how much there is, and how often it happens. They will also ask about your family history of colon cancer or polyps.

A digital rectal exam is often the first step. The doctor inserts a gloved finger into the rectum to feel for abnormalities. This can detect hemorrhoids, masses, or tenderness.

A colonoscopy is the most reliable way to find the cause of rectal bleeding. The doctor uses a flexible tube with a camera to examine the entire colon. If polyps or abnormal tissue are found, they can be removed or biopsied during the same procedure.

Other tests may include a flexible sigmoidoscopy, which examines only the lower part of the colon, or a CT scan to look for structural problems. Stool tests can check for hidden blood or signs of infection.

Do not assume the bleeding is just hemorrhoids. While hemorrhoids are common, they can coexist with more serious conditions. A doctor needs to rule out other causes before settling on a diagnosis.

Why You Should Not Self-Treat Without a Diagnosis

Over-the-counter creams and ointments for hemorrhoids are widely available. They can reduce itching and discomfort. But using them without knowing the cause of the bleeding can delay a serious diagnosis.

Colon cancer often bleeds slowly. The blood may not be visible in every stool. By the time symptoms become noticeable, the cancer may have grown. Early detection through proper evaluation dramatically improves outcomes.

If the bleeding is from an anal fissure, increasing fiber and water intake can help soften stools and reduce strain. But if the bleeding is from a polyp or cancer, no amount of fiber will fix it. The only way to know is to have the bleeding investigated.

There is no reliable way to tell the difference between harmless and serious causes of rectal bleeding at home. The color, amount, and frequency of bleeding do not reliably predict the cause.

What to Expect During Recovery and Treatment

Treatment depends entirely on the cause. Hemorrhoids and anal fissures often improve with increased fiber, adequate hydration, and stool softeners. Warm sitz baths can reduce discomfort. Some hemorrhoids require procedures to remove or shrink them.

Diverticular bleeding often stops on its own. If it does not, a doctor may need to intervene during a colonoscopy to stop the bleeding. Severe cases may require surgery.

Inflammatory bowel disease is managed with medications that reduce inflammation. These include aminosalicylates, corticosteroids, and biologic therapies. The goal is to control inflammation and prevent flare-ups.

Polyps found during colonoscopy are usually removed immediately. This prevents them from growing and potentially becoming cancerous. After polyp removal, you may need more frequent colonoscopies to monitor for new growths.

Colorectal cancer treatment depends on the stage. Surgery to remove the tumor is common. Chemotherapy and radiation may be used in addition to surgery. The earlier the cancer is found, the better the chances of successful treatment.