In most cases, bright red blood indicates bleeding in the lower colon or rectum, while darker red blood is a sign of bleeding in the small bowel or upper colon.
Very dark or black-red blood is often associated with bleeding in the stomach or other organs in the digestive system.
In this article, we examine 11 causes of rectal bleeding, along with other symptoms that each one can prompt. We also look at when rectal bleeding should be referred to a doctor.
A wide range of health conditions and factors can cause or add to rectal bleeding.
Some of the most common causes include:
Hemorrhoids are a common and treatable cause of rectal bleeding.
Hemorrhoids are inflamed anal blood vessels, and they are extremely common. They can develop on the outside or inside of the anus, appearing as small bumps that occasionally bleed during bowel movements or when wiping.
- chronic constipation and straining
- chronic diarrhea
- straining during bowel movements or sitting on the toilet for too long
- low fiber or unbalanced diet
Hemorrhoids usually respond well to over-the-counter creams and suppositories that contain hydrocortisone. Taking warm baths frequently, eating a high-fiber diet, and using stool softeners can also help reduce the discomfort of hemorrhoids.
If initial treatments fail, a doctor may perform minor surgery to remove the hemorrhoids.
A fistula occurs when an abnormal opening or pocket develops between two neighboring organs. Fistulas that appear between the anus and rectum, or anus and skin, can cause a discharge of white fluid and blood.
Fistulas are sometimes treated with antibiotics, but they may require surgery if they progress.
Fissures occur when tissues lining the anus, colon, or rectum are torn, resulting in pain and rectal bleeding.
Warm baths, a high-fiber diet, and stool softeners can all help reduce symptoms of fistula. In severe cases, fissures may require prescription creams or surgery.
Diverticulosis is when small pockets called diverticula develop on the walls of the colon around a weakness in the organ's muscular layers.
These pockets or diverticula are extremely common. Sometimes diverticula can start bleeding, but this bleeding usually stops on its own.
Usually, these pockets do not cause symptoms or require treatment unless they become infected, which is when a condition called diverticulitis occurs.
Infected and inflamed diverticula are often painful and can cause rectal bleeding, usually a moderate rush of blood that flows for a few seconds.
Diverticulitis is treated with antibiotics and, if severe, surgery.
5. Proctitis or colitis
Proctitis occurs when the tissues that make up the rectum become inflamed, often resulting in pain and bleeding.
Colitis occurs when the tissues lining the colon become inflamed. A type of colitis called ulcerative colitis can also cause ulcers, or open, progressive sores, that are prone to bleeding.
Treatments for proctitis and colitis vary, depending on the causes and range from antibiotics to surgery.
Common causes of proctitis and colitis include:
- some conditions that cause digestive problems, such as irritable bowel syndrome (IBS) and Crohn's disease
- some medications, such as blood thinners
- radiation or chemotherapy
- anal intercourse
- reduced blood flow to the colon or rectum
- a blockage in the colon or rectum
Treatment for gastroenteritis usually involves fluids, rest, and antibiotics or antivirals, depending on the cause.
7. Sexually transmitted infections (STIs)
Unprotected sexual intercourse that involves the anal area can spread a wide range of viral and bacterial diseases. These can cause inflammation of the anus and rectum. Inflammation, if it occurs, increases the likelihood of bleeding.
Treatment for STIs usually involves either an antibiotic, antiviral, or antifungal medication, depending if the cause is bacterial, viral, or fungal.
Weakened rectal tissues can allow a portion of the rectum to push forward or bulge outside of the anus, usually resulting in pain and, almost always, bleeding.
Prolapse is more common in older adults than in younger people. Some people with this condition may require surgery to correct it.
Polyps are noncancerous, abnormal growths. When polyps grow on the lining of the rectum or colon they can cause irritation, inflammation, and minor bleeding.
In many cases, a doctor will remove polyps so they can be tested for signs of cancer and to avoid the risk of them becoming cancerous.
10. Colon or rectal cancer
Colon cancer is a very common form of cancer and tends to progress slowly, so it is often treatable if caught early.
Rectal cancer, while far rarer than colon cancer, is also usually curable if detected and treated in time.
Some cases of colon and rectal cancer develop from initially benign polyps. All cases of gastrointestinal cancer require treatment, which usually involves a combination of chemotherapy, radiation therapy, and surgery.
11. Internal bleeding
Major injury to any of the gastrointestinal organs can result in internal bleeding that passes through the rectum. Severe gastrointestinal disease can also lead to internal bleeding.
Internal bleeding almost always requires hospitalization and surgery.
When to see a doctor
Ongoing or worsening rectal bleeding should be assessed by a doctor.
Occasional minor to mild rectal bleeding is extremely common and will often not need medical attention or treatment.
Severe, chronic, or painful rectal bleeding may be a sign of a more serious underlying condition and should be assessed by a doctor.
People normally notice rectal bleeding when they see streaks or drips of blood in their stool, the toilet bowl, or when wiping. Some people might also find blood in their underwear, or the toilet water may appear reddish-pink after they go to the bathroom.
Some cases of rectal bleeding also cause very bad smelling, dark, tarry stool mixed with very dark red to black blood.
Reasons to see a doctor for rectal bleeding include:
- bleeding that lasts longer than 2 or 3 weeks
- children with bloody stool or rectal bleeding
- unexplained weight loss, fatigue, or weakness as well
- painful, swollen, or tender abdomen
- accompanying fever
- simultaneous lumps in the abdomen
- stool that is thinner, longer, or softer than normal for 3 weeks or more
- accompanying nausea or vomiting
- accompanying long-term constipation or changes in bowel habits
- associated uncontrolled leakage from the anus
Reasons to seek emergency care for rectal bleeding include:
- vomiting or coughing up blood
- blood running from the nose, eyes, or ears
- bleeding that is very dark red or black
- the reason of bloody diarrhea is unclear, such as unrelated to an abdominal condition or medical treatment
- loss of consciousness or confusion
- extreme abdominal or lower back pain
Tests and diagnosis
If bleeding is associated with an already diagnosed medical condition, a doctor will discuss ways to manage, reduce, and track symptoms.
If the cause of rectal bleeding is unknown, a doctor will normally ask questions about symptoms and the person's medical history.
Depending on the severity, frequency, and accompanying symptoms, the doctor will work out if further testing is required. A doctor may also make a referral to a gastrointestinal or colorectal specialist.
Common tests associated with rectal bleeding include:
- a physical examination of the anus and rectum
- analysis of a stool sample
Specialists may perform additional tests that might include:
- colonoscopy or flexible sigmoidoscopy where the colon is examined by the insertion of a tube with a camera
- anoscopy where a device is inserted into the anus to examine the tissue
- biopsy or removal of a small tissue sample for examination
- computed tomography or CT scan that provides a 3-D image
Eating high-fiber foods may help to prevent rectal bleeding.
In some cases, there is no real way to prevent minor cases of rectal bleeding. However, some factors are known to cause, contribute to, or worsen rectal bleeding.
Common prevention tips for rectal, colon, and anal bleeding include:
- eating a balanced diet that is high in fiber
- always staying hydrated
- not straining when going to the washroom
- wiping the anus gently
- treating chronic or prolonged constipation with over-the-counter remedies, such as stool softeners, which are available online
- treating chronic or prolonged diarrhea with over-the-counter remedies, such as bismuth subsalicylate, which is available online
- trying not to lift heavy objects unless required
- maintaining a healthy body weight
- taking long, warm baths frequently if experiencing symptomsfollowing treatment plans set out by a doctor for related medical conditions
- trying to avoid spicy, rich, fatty, heavily processed, and refined foods
- seeing a doctor about abnormal growths in the area
- avoiding overuse of non-steroidal anti-inflammatory (NSAID) drugs
- wearing a condom during sex
People may wish to talk to a doctor about gastrointestinal symptoms that may be a sign of underlying conditions, including infections, digestive conditions, or abnormal growths.
Should you worry?
A few occasional drops or streaks of blood in the toilet, when wiping, or in the stool, is usually not a worry.
Some people may avoid talking with their doctor about rectal bleeding out of embarrassment and anxiety, even in moderate or severe cases. While rare, heavy or chronic rectal bleeding can cause serious blood loss or be a sign of an underlying condition that requires treatment.
People should see a doctor about rectal bleeding that is chronic or noticeable, abnormal growths around the anus. It is also a good idea to talk with a doctor about rectal bleeding that does not respond to home remedies.
People should seek emergency medical attention for rectal bleeding or stool that is very dark, especially if they are also vomiting or coughing up blood. It is also vital to seek immediate help for bleeding that lasts for more than a few minutes or is accompanied by other symptoms, such as severe pain, fever, or weakness.