Rectal Bleeding: Causes & When to Have a Colonoscopy | GI Doc

Rectal bleeding, warning signs, and colonoscopy are important topics to understand because the same visible symptom can have several different causes. A small amount of bright red blood may come from a haemorrhoid or anal fissure, but its appearance alone cannot confirm a diagnosis.

Bleeding deserves a medical assessment, especially if it happens repeatedly or occurs with other symptoms. The aim is to find the source, provide the right treatment, and avoid overlooking a condition that benefits from early diagnosis.

What Does Rectal Bleeding Look Like?

Rectal bleeding may appear as a streak on toilet paper, drops in the bowl, blood coating the stool or blood mixed with it. Some people notice mucus as well. The colour may be bright red, dark red or maroon. Black, tar-like stools can also indicate gastrointestinal bleeding, often from higher in the digestive tract, although some medicines and foods may darken stools.

These details help a doctor decide what to investigate, but colour does not reliably identify the cause by itself. Even bright red blood, which often comes from near the anus or rectum, can sometimes reflect bleeding farther along the colon. Tell your doctor how much blood you saw, how often it occurred and whether it appeared before, during or after a bowel movement.

 

Common Causes of Rectal Bleeding

 

Haemorrhoids and anal fissures

Haemorrhoids are swollen blood vessels in or around the anus. They can cause bright red bleeding, sometimes with itching, discomfort or a lump. Internal haemorrhoids may bleed without much pain. An anal fissure is a small tear in the anal lining, often associated with constipation or passing a hard stool. It commonly causes sharp pain during and after a bowel movement, along with a little bright red blood.

These are frequent explanations, but finding a haemorrhoid does not automatically rule out another source of bleeding. A clinician may still recommend further investigation based on the person’s history and examination.

Inflammation and infection

Inflammation of the colon or rectum can produce blood, sometimes with diarrhoea, mucus, abdominal pain or a strong urge to pass stool. Causes include infections and inflammatory bowel disease (IBD), particularly ulcerative colitis and some forms of Crohn’s disease. Symptoms, examination findings and stool tests help guide the next steps; biopsies taken during colonoscopy may help confirm certain diagnoses.

Dr Deetlefs’ guide to Crohn’s disease and ulcerative colitis explains how these conditions affect the bowel.

Diverticular bleeding and abnormal blood vessels

Diverticula are small pouches in the wall of the colon. A blood vessel associated with one of these pouches can bleed, sometimes suddenly and without pain. Abnormal blood vessels in the colon may also cause intermittent bleeding. A larger or persistent bleed requires urgent assessment, regardless of whether it hurts.

Polyps and colorectal cancer

Colon polyps are growths on the lining of the colon or rectum. Many cause no symptoms, but some can bleed. Certain polyps may develop into cancer over time, which is one reason finding and removing them matters. Colorectal cancer can also cause rectal bleeding, a change in bowel habits, abdominal symptoms or iron-deficiency anaemia, although these signs have many possible explanations.

Bleeding does not mean a patient has cancer. It does mean the cause should be established instead of assumed. Learn more about how polyps are treated in GI Doc’s polypectomy guide.

Which Warning Signs Need Medical Attention?

Arrange a medical appointment for any unexplained rectal bleeding, particularly if it recurs or does not settle. Assessment is especially important when bleeding accompanies:

• A persistent change in bowel habits, such as new diarrhoea or constipation
• Unexplained weight loss or reduced appetite
• Ongoing abdominal pain, rectal pain or a feeling that the bowel does not empty
• Fatigue, breathlessness or a blood test showing iron-deficiency anaemia
• A personal history of polyps or IBD, or a family history of colorectal cancer

Seek urgent medical care for black or dark red stools, bloody diarrhoea, or bleeding that is heavy, ongoing or accompanied by clots. Go to an emergency department immediately if bleeding occurs with fainting, marked dizziness, confusion, severe weakness, a racing heartbeat or severe abdominal pain. These can be signs of substantial blood loss or another acute illness.

 

How Will a Doctor Investigate the Bleeding?

An assessment starts with a conversation about the bleeding pattern, pain, bowel movements, medications, medical history and family history. Your doctor may examine the abdomen and anal area and perform a digital rectal examination. This can help identify a fissure, haemorrhoid or other abnormality close to the anus.

Depending on the findings, blood tests may check for anaemia or inflammation. Stool tests may be useful when infection or bowel inflammation is suspected. Some patients need a closer look at the anal canal or lower bowel with anoscopy or flexible sigmoidoscopy. Others may need a colonoscopy, which examines the entire colon and rectum. The choice is individual: a small amount of bleeding in a younger person with an obvious fissure is assessed differently from recurrent bleeding with anaemia or a family history of colorectal cancer.

An examination of the anal area is useful, but it cannot show what is happening throughout the colon. That is why a doctor may recommend additional testing even when haemorrhoids are present.

When Might a Colonoscopy Be Recommended?

A colonoscopy may be recommended when the cause remains unclear, bleeding persists or returns, or a person’s symptoms and risk factors warrant a full examination of the colon. It is also considered when there are concerning features such as a change in bowel habits, unexplained weight loss, iron-deficiency anaemia, an abnormal examination or a relevant personal or family history.

Age matters, but there is no age below which persistent bleeding can simply be dismissed. The decision to investigate a symptom is separate from a routine screening schedule for someone with no symptoms. A clinician will weigh the whole picture and explain why colonoscopy or another test is appropriate.

During colonoscopy, a gastroenterologist passes a thin, flexible camera through the rectum to inspect the lining of the colon. The examination may reveal inflammation, ulcers, diverticula, bleeding points or polyps. Tissue samples can be taken for laboratory analysis, and some polyps can be removed during the same procedure. Certain bleeding lesions can also be treated endoscopically when appropriate.

Patients receive instructions for bowel preparation beforehand. A clean bowel is essential for a careful examination. Sedation is commonly used, and patients should arrange a lift home and follow the practice’s recovery instructions. For a fuller explanation, see GI Doc’s colonoscopy: what to expect page.

What Happens After the Cause Is Found?

Treatment depends on the diagnosis, not simply the appearance of blood. A fissure or haemorrhoids may respond to measures that reduce straining and treat constipation, although persistent symptoms sometimes require additional treatment. An infection or inflammatory condition may need tests and targeted medication. A bleeding polyp may be removed, and a suspicious lesion requires biopsy and a clear follow-up plan.

When a colonoscopy does not identify the source, your gastroenterologist will consider whether the bleeding has stopped, whether anaemia is present and whether further assessment is necessary. The plan may involve follow-up, another type of endoscopy or other investigations. The result should be discussed with you, including any biopsy findings and when to seek help if bleeding returns.

Conclusion

Rectal bleeding has many possible causes, from common anal conditions to inflammation, polyps and cancer. The amount and colour of blood can provide clues, but neither can give a reliable diagnosis on its own. Persistent, recurrent or unexplained bleeding should be assessed, and heavy bleeding or symptoms of significant blood loss need urgent medical attention.

Colonoscopy is one way to examine the colon, take biopsies and sometimes treat a problem during the same procedure. Whether it is needed depends on your symptoms, examination, blood results, age and personal and family history.

If you have noticed blood in your stool or after a bowel movement, arrange an individual assessment with Dr Eduan Deetlefs at GI Doc Cape Town.

Telephone: 021 202 0626
Email: info@gidoc.co.za
Address: Suite 304, 3rd Floor, The Park Building, Park Road, Pinelands, Cape Town, 7405
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