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Blood in your stool can have many possible causes. Some, such as haemorrhoids and anal fissures, are common, while others include diverticular disease, inflammatory bowel disease, colorectal polyps and colorectal cancer.
The appearance of the blood can provide clues about where bleeding may originate. Bright-red blood often comes from the lower part of the digestive tract, while darker blood or black, tarry stools may indicate bleeding from higher up in the gastrointestinal tract. However, the appearance of blood alone cannot determine the cause.
Understanding the pattern of bleeding and accompanying symptoms will help you know when further investigation may be needed and when to seek medical assessment.
Blood in the stool may appear as bright-red streaks on the surface of the stool, be mixed into the stool, turn the stool dark red or maroon, or make it appear black and tarry. Its appearance can provide clues to where bleeding may be occurring, but it cannot determine the cause on its own.
| What you may notice | What it may suggest | Possible sources or causes |
|---|---|---|
| Bright-red blood | Bleeding is often from the lower part of the digestive tract or anal canal | Haemorrhoids, anal fissures or conditions affecting the rectum or colon |
| Blood mixed with stool | Bleeding may be coming from within the rectum or colon | Inflammation, diverticular disease, colorectal polyps or colorectal cancer |
| Dark-red or maroon stool | Bleeding may originate from the upper part of the colon or, sometimes, higher in the digestive tract | Diverticular bleeding and other gastrointestinal causes |
| Black, tarry stool | May indicate digested blood from the upper gastrointestinal tract | Bleeding from the stomach or small intestine |
Blood in the stool can result from conditions affecting the anus, rectum or colon, ranging from relatively common problems such as haemorrhoids to colorectal cancer. The need and urgency to seek medical attention depends on factors such as the appearance of the bleeding, associated symptoms, age, medical history and changes in bowel habits.
Haemorrhoids (piles) are a common cause of bright-red rectal bleeding. They are enlarged blood vessels in or around the anus, and bleeding may appear on toilet paper, in the toilet bowl or coat the stool during or after a bowel movement. Other symptoms can include itching, discomfort or a lump around the anus, although internal haemorrhoids may bleed without causing pain.
An anal fissure is a small tear in the lining of the anal canal, often associated with passing hard or large stools. It commonly causes bright-red bleeding together with sharp pain during or after a bowel movement. The blood is usually noticed on toilet paper or on the outside of the stool.
Diverticular disease can cause noticeable darker-red or maroon rectal bleeding when a blood vessel associated with a diverticulum bleeds. Diverticula are small pouches that develop in the wall of the colon. Diverticular bleeding is distinct from diverticulitis, which occurs when diverticula become inflamed or infected and more commonly causes abdominal pain and fever.
Ulcerative colitis and Crohn's disease, which are less common, can cause inflammation and ulceration within the digestive tract. Depending on the area affected, this may result in blood or mucus in the stool. Other symptoms can include persistent diarrhoea, abdominal pain, urgency to pass stool and weight loss.
Colorectal polyps are growths that develop on the inner lining of the colon or rectum. Some can bleed, although many cause no noticeable symptoms and are only detected during colorectal screening or investigation. Certain types of polyps can develop into colorectal cancer over time, which is one reason appropriate detection and removal can be important. Removal of polyps may reduce the chance of a person developing colorectal cancer.
Colorectal cancer can cause rectal bleeding or blood mixed with the stool, but bleeding may sometimes be too little to see. Other possible signs include a persistent change in bowel habits, unexplained weight loss, abdominal discomfort or iron-deficiency anaemia. These symptoms can have other causes, so further assessment is needed to determine what is responsible.
Blood in your stool should be medically assessed if it is persistent, recurrent or unexplained, particularly when it occurs with changes in bowel habits, unexplained weight loss, ongoing abdominal symptoms, iron-deficiency anaemia or a family history of colorectal cancer.
Even if haemorrhoids or another common condition seem like a possible explanation, the source of recurrent bleeding should not automatically be assumed. Arrange a medical assessment with a colorectal specialist if you notice:
Heavy bleeding, black and tarry stools, fainting, marked dizziness, weakness or other signs of significant blood loss require more urgent medical attention.
To determine where the bleeding is coming from, your doctor will usually ask about its appearance and frequency, your bowel habits, accompanying symptoms and relevant medical or family history. This may be followed by an abdominal and rectal examination.
Depending on the findings, further investigation may include:
The appropriate test depends on the character and pattern of bleeding, symptoms, examination findings and individual risk factors. Identifying the source is important because correct treatment depends on an accurate diagnosis.
Blood in your stool can have many possible causes, and it is not always possible to tell where the bleeding is coming from based on its appearance alone. If the bleeding persists, recurs or occurs alongside changes in bowel habits or other concerning symptoms, it is important to get a medical assessment to identify the underlying cause.
At Teoh Colon, Rectum & General Surgery, patients with rectal bleeding and other gastrointestinal concerns can be assessed with appropriate examinations and investigations, including endoscopic procedures where indicated. Treatment can then be recommended according to the condition identified and the individual findings.
If you have noticed blood in your stool or an unexplained change in your bowel habits, schedule a consultation with Dr Teoh Tiong Ann for further assessment.
Book an AppointmentYes. Small amounts of blood may not be visible to the eye and may only be detected through stool tests such as a faecal immunochemical test (FIT) or faecal occult blood test (FOBT). Occult or unnoticeable blood may have several causes. A positive FIT or FOBT will require further investigation to determine where the bleeding is coming from.
Bright-red blood on toilet paper or coating the outside of the stool may occur with conditions affecting the anus or lower rectum, including haemorrhoids and anal fissures. Blood mixed into the stool may suggest bleeding from within the rectum or colon. However, the appearance and location of the blood cannot confirm its cause, so persistent, recurrent or unexplained bleeding should be properly assessed.
Yes. Both haemorrhoids and colorectal cancer can cause rectal bleeding. The presence or colour of blood alone cannot reliably distinguish between them. Persistent or recurrent bleeding, particularly with other bowel changes or risk factors — especially a family history of cancer — should be properly assessed rather than assumed to be caused by haemorrhoids.
No. Not every episode of rectal bleeding requires a colonoscopy. Whether one is recommended depends on factors such as your symptoms, age, medical and family history, examination findings and the suspected source of bleeding. Other examinations or tests may sometimes be appropriate first. Your doctor will advise you on the best course of action.
Heavy bleeding, black and tarry stools, fainting, marked dizziness, weakness or other signs of significant blood loss require more urgent medical attention. For bleeding that is persistent, recurrent or unexplained without these urgent symptoms, arrange a medical assessment to determine the underlying cause.
Dr Teoh Tiong Ann
Consultant General and Colorectal Surgeon
MBBS (S'pore), M.Med (Surgery) (S'pore), FRCS (Edin), FAMS
Dr Teoh Tiong Ann is a Consultant General and Colorectal Surgeon with extensive experience in surgical care. He received subspecialty training at Cleveland Clinic Florida under Singapore's Health Manpower Development Plan and has been involved in professional surgical societies in Singapore and internationally. He currently practises at Mount Elizabeth Hospital.
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