Blood in stool (rectal bleeding): causes, when to worry, and when to have a colonoscopy

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Can the appearance of blood in stool give clues to where it is coming from?

There are some features which can help predict where the blood is coming from. However, it is important to note that these 'clues' are not hard and fast rules - we can never know with complete certainty where the blood is coming from without visually examining inside.

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• Spots or streaks on the paper, dripping blood at the end of the motion, or bright red blood separate to the stool: May indicate bleeding from near the exit of the bowel, i.e. the anus or rectum

• Darker red blood or blood mixed in with the stool: May indicate bleeding from higher up in the colon or small bowel

• Jet black or tar-like stools: Suggests bleeding from the upper gastrointestinal tract (stomach region)

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Is blood in the stool serious?

Having blood in the stools is never 'normal', and always indicates an underlying problem. In many cases, the problem may be something simple (and benign) such as haemorrhoids. However, blood in the stool can also be the presenting symptom of serious conditions, including bowel cancer. The cause of bleeding cannot be determined with certainty based simply on the appearance. For this reason, you should always consult a doctor when you see blood in the stool.

 

What conditions might cause blood in the stool?

There are a wide variety of conditions, both benign and more serious, that can lead to blood in the stool. Common conditions include:

• Haemorrhoids: Bulging, enlarged veins in the rectum. The surface of these veins is fragile, and can be prone to bleeding during passage of a stool, especially if the person is straining excessively or has hard stools (constipation).

• Anal fissure: Small, painful tears in the lining of the anus. You may experience pain when passing a motion, along with bleeding.

• Bowel infections ("gastro" or "tummy bug"): May cause bloody diarrhoea, though bleeding should always subside within a week at most.

• Bowel cancer: Most concerning cause of blood in stool.

• Bowel polyps: Growths in the colon that can turn cancerous if left unchecked.

• Inflammatory bowel disease (Crohn's and ulcerative colitis): Condition causing swelling and inflammation of the intestines, and can cause bloody diarrhoea or frank blood in the stools.

• Diverticular disease: A condition where pouches form on the wall of the colon. It is more common with increasing age, and can cause profuse bleeding that usually subsides within a week.

 

When should I consult a doctor?

Blood in the stool is never 'normal' and therefore you should always consult your local doctor or gastroenterologist for a proper assessment. 

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When is colonoscopy recommended for blood in stool?

A colonoscopy is often recommended when rectal bleeding is recurrent, the source is unclear, or there are features suggesting bleeding from higher in the colon.

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Colonoscopy is commonly advised if you have:

• blood mixed through the stool 

• bleeding that is recurrent or increasing

• iron deficiency or anaemia

• a change in bowel habit (e.g. new diarrhoea, constipation, narrower stools)

• unexplained weight loss or persistent abdominal pain

• a personal or family history of bowel polyps, bowel cancer or inflammatory bowel disease

• age where bowel cancer screening becomes relevant, or new bleeding later in life

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If bleeding appears to be classic for a benign cause such as haemorrhoids (bright red on toilet paper, pain with opening bowels), you may not always need an immediate colonoscopy - but you still need a medical review to confirm this and ensure nothing else is being missed.

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Sydney: If you'd like an assessment, you can book a consultation or in most cases proceed directly to colonoscopy depending on your symptoms and referral details.

 

What tests might I require?

Your doctor or gastroenterologist may perform/order some of the following:

• Rectal examination: Your doctor will examine inside the end of your rectum using a gloved finger. This can detect major abnormalities at the very end of the bowel. If you will be having a colonoscopy, rectal examination can be performed while you are asleep under sedation so that there is no discomfort for you.

• Sigmoidoscopy: A 'short colonoscopy' that can visualise approximately the bottom third of your colon

• Colonoscopy: The 'gold standard' test to evaluate the bowels in cases of blood in the stool. Allows for a definitive examination of the entire colon and end of the small intestine to look for the presence of any of the conditions that cause blood in the stool.

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Your gastroenterologist is best placed to advise you on which of these tests are necessary. However, in most cases, colonoscopy is recommended for anyone over the age of 40 with blood in the stools; it is sometimes required in younger persons too.

 

Can I do anything before seeing the doctor?

You can try some of the following simple measures if the bleeding is mild:

• Take a soluble fibre supplement (e.g. psyllium husk) - Helps improve the consistency of the stool and may reduce bleeding from some anal and rectal causes.

• Laxatives - Useful if you are constipated, have hard stools or need to strain excessively to pass a motion. Making the stool softer can reduce bleeding. You can obtain laxatives over the counter at the chemist.

• Haemorrhoid ointments - If the bleeding is thought to be haemorrhoidal in origin, these ointments are simple, safe and may be effective in reducing the bleeding.

 

What is the treatment for blood in the stools?

Once the cause is determined then treatment is directed at the specific cause. Many causes of bleeding identified at colonoscopy can be treated then and there by an experienced gastroenterologist. For examples, polyps can be removed and abnormal blood vessels can be cauterised.

 

Who should I consult in Sydney regarding blood in my stools?

Enlist the services of an expert in gastrointestinal disorders and diagnostic and therapeutic colonoscopy, A/Professor Santosh Sanagapalli. You may request an appointment for consultation, or if you already know that a colonoscopy is required you may click here to book directly on for a colonoscopy.

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FAQs: blood in stool / rectal bleeding (Sydney)

Is blood in stool always bowel cancer?

No. Haemorrhoids and anal fissures are common benign causes, but bleeding should always be assessed by a medical professional, especially if recurrent or accompanied by red flag features.​

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Do haemorrhoids mean I don't need a colonoscopy?

Not always. Haemorrhoids might coexist with another cause of bleeding. A doctor such as a gastroenterologist can assess your risk factors and symptoms to decide if colonoscopy is recommended.​

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What does bright red blood vs dark blood vs black stool mean?

In general, the brighter red the colour of the blood​, the more suggestive that the bleeding is arising from lower down in the gastrointestinal tract. Black, tarry stool (melaena) can indicate upper GI bleeding and should always be assessed by a medical professional urgently.

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When should I go to Emergency?

Attend your local emergency department if you have heavy bleeding in the stools and any of the following:

• Feeling dizzy or faint

• Low blood pressure or racing heart rate

• Feeling very lethargic, tired or weak

• Black, tarry stools

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What happens during a colonoscopy?

A thin camera is used to examine the bowel lining whilst you are sedated. Polyps and some other causes of bleeding can often be treated during the procedure itself, and biopsies can be taken if needed.

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How do I book a colonoscopy in Sydney?

You can book a consultation first, or in some cases proceed directly to colonoscopy depending on your circumstances and referral details.​