Rectal Bleeding: Causes and When to Worry

What rectal bleeding looks like

Doctors call bright or dark red blood from the bottom hematochezia. The appearance gives clues to where it comes from:

Foods and medicines can mimic blood. Beets, red food coloring and tomato skins can turn stool red, and iron tablets and bismuth (Pepto-Bismol) turn it black.

Common causes of rectal bleeding

Hemorrhoids

Hemorrhoids are swollen blood vessels in and around the anus. They are the most common cause of rectal bleeding. Internal hemorrhoids usually bleed painlessly: bright red blood on the paper or dripping into the bowl after a bowel movement. They may bulge out (prolapse) and go back in. External hemorrhoids can form a painful, purple lump if a clot develops. Straining, constipation, pregnancy and prolonged sitting on the toilet make them worse.

Anal fissure

An anal fissure is a small tear in the lining of the anus, usually from passing a hard stool. The key feature is sharp, cutting pain during and after a bowel movement, often lasting an hour or more, with a little bright red blood on the paper.

Diverticular bleeding

Diverticulosis means small pouches in the colon wall, common after 50. A blood vessel in a pouch can bleed suddenly, causing a large, painless passage of dark red or maroon blood. It often stops by itself but needs hospital assessment.

Inflammatory bowel disease and infections

Ulcerative colitis and Crohn's disease cause bloody diarrhea with mucus, urgency, cramping and sometimes weight loss. Infections such as Campylobacter, Shigella, E. coli and C. difficile cause bloody diarrhea with fever. Proctitis, inflammation of the rectum alone, causes bleeding, mucus and a constant urge to pass stool.

Serious causes not to miss

Bowel polyps and colorectal cancer

Colorectal polyps are growths on the bowel lining. Some slowly become cancer. Both can cause bleeding that may be visible or hidden. Colorectal cancer is more likely if bleeding comes with:

• a change in bowel habit lasting more than 3 weeks, especially looser or more frequent stools
• blood mixed into the stool rather than on the surface
• unexplained weight loss or tiredness from iron deficiency anemia
• a feeling of incomplete emptying, or a lump in the abdomen or rectum
• age over 45, or a strong family history

Bowel cancer is increasing in adults under 50, so new rectal bleeding at any age should not simply be assumed to be hemorrhoids if it persists or has any of these features.

Other causes

• Angiodysplasia: fragile blood vessels in the bowel wall, more common in older adults.
• Ischemic colitis: reduced blood flow to the colon causes sudden cramping pain followed by bloody stool, usually in older adults.
• Upper GI bleeding: a fast-bleeding stomach ulcer can produce red or maroon blood. See gastrointestinal bleeding.
• Anal cancer, rectal prolapse and injury.
• Radiation proctitis after pelvic radiotherapy.

Rectal bleeding with no pain

Painless bright red bleeding is typical of internal hemorrhoids, but it is also how polyps, early cancer, diverticular bleeding and angiodysplasia present. Pain during bowel movements points more toward a fissure or thrombosed hemorrhoid. Lack of pain is reassuring only in younger people with a clear hemorrhoid history and no other warning signs.

When to worry about rectal bleeding

See a doctor promptly if:

• you are 45 or older and have not had bleeding investigated
• the blood is dark, mixed into the stool, or comes with mucus
• you have a change in bowel habit, weight loss, abdominal pain or fatigue
• bleeding keeps coming back
• you have a family history of bowel cancer or inflammatory bowel disease

Get emergency help for heavy bleeding, clots, or signs of significant blood loss such as dizziness or fainting.

How doctors find the cause

1. History: color and amount of blood, its relation to bowel movements, pain, bowel habit, weight, medicines (especially blood thinners, aspirin and NSAIDs) and family history.
2. Examination: abdominal examination, inspection of the anus, and a digital rectal exam.
3. Anoscopy or proctoscopy: a short tube to view hemorrhoids and the lower rectum, done in the clinic.
4. Blood tests: complete blood count for anemia, iron studies, and clotting tests.
5. Fecal immunochemical test (FIT): detects hidden blood and helps decide how urgently to investigate.
6. Flexible sigmoidoscopy or colonoscopy: a camera examination of part or all of the colon. Colonoscopy is the main test to exclude polyps, cancer and colitis, and polyps can be removed during it.
7. For heavy bleeding: CT angiography, upper endoscopy, or capsule endoscopy for small bowel sources.

Treatment

Treating the cause

• Hemorrhoids: fiber, fluids, avoiding straining, creams for symptoms; rubber band ligation or surgery if bleeding persists.
• Fissures: stool softeners and prescription ointments that relax the anal muscle; Botox or a small operation if they do not heal within 6 to 8 weeks.
• Colitis: anti-inflammatory and immune-modifying medicines.
• Polyps: removal during colonoscopy.
• Cancer: surgery, often with chemotherapy or radiotherapy.
• Heavy bleeding: hospital care with fluids, transfusion if needed, and endoscopic or radiological procedures to stop the bleeding.

Home care for minor bleeding

• Eat 25 to 35 grams of fiber a day from vegetables, fruit, whole grains and beans, or a fiber supplement.
• Drink enough fluid to keep stools soft.
• Do not strain or sit on the toilet for long periods, and avoid reading on the toilet.
• Use warm sitz baths for 10 to 15 minutes for hemorrhoid or fissure discomfort.
• Gently pat clean with moist, unscented wipes.

Frequently asked questions

Is bright red blood when wiping serious?

Usually not. Bright red blood on the toilet paper is most often from hemorrhoids or a small anal tear. It still needs a check if it keeps happening, if you are 45 or older, or if it comes with a change in bowel habit, weight loss or tiredness.

When should I worry about rectal bleeding?

Worry if bleeding is heavy, contains clots, is dark or mixed with stool, comes with dizziness or abdominal pain, or occurs with weight loss or a lasting change in bowel habit. These need prompt medical review, and heavy bleeding or fainting needs 911.

Can stress cause rectal bleeding?

Stress does not directly cause bleeding, but it can worsen constipation, diarrhea and flares of inflammatory bowel disease, which can lead to bleeding. Any repeated bleeding should still be investigated rather than put down to stress.

What does it mean if blood is mixed in my stool?

Blood mixed into the stool usually comes from higher in the colon or rectum rather than the anus. Causes include colitis, infection, polyps and bowel cancer. It needs a doctor's assessment and often a colonoscopy.

Do I need a colonoscopy for rectal bleeding?

Not always. A young person with clear hemorrhoids or a fissure may only need an examination. Colonoscopy is recommended for people 45 or older, those with warning signs such as anemia or bowel habit change, a family history, or bleeding that does not settle with treatment.

Can hemorrhoids cause a lot of blood?

Hemorrhoids can make the toilet water look very red even from a small amount of blood, which can be alarming. Truly heavy or continuous bleeding, clots or feeling faint is unusual from hemorrhoids and needs emergency assessment.