Investigation of blood in the stool

Blood in stool: Causes, examination, and treatment

Call 112 (the Danish emergency number) if you have heavy bleeding, fainting, or clear signs of circulatory compromise such as marked dizziness, pale clammy skin or a markedly affected general condition. Contact a doctor or the out-of-hours service the same day for black, tarry stools, larger amounts of fresh blood, or bleeding together with fever and severe abdominal pain.

If you experience blood in your stool, it's natural to be concerned. This is a symptom that should always be taken seriously and investigated by a specialist, regardless of whether it's a small amount of fresh blood on the toilet paper or darker blood mixed in with the stool. The assessment is based on the appearance of the bleeding, the accompanying symptoms and other risk factors.

Common and other possible causes

In many cases, the bleeding is due to harmless conditions. The most common causes include:

• Hemorrhoids: This is one of the most common causes of fresh, bright red blood. Hemorrhoids are swollen blood vessels at the anal opening that can cause itching, burning, and bleeding, often in connection with bowel movements.

• Fissures (Anal fissures): Small tears in the mucous membrane at the anal opening can occur with hard stools. This often causes sharp pain and small amounts of fresh blood.

• IBD (Inflammatory Bowel Disease): Diseases such as Colitis Ulcerosa or Crohn's disease (collectively referred to as IBD) can cause inflammation in the intestine, which often leads to bloody diarrhea and abdominal pain.

Focus on early detection of bowel cancer

Although the cause is often benign, the most important reason for being examined is to rule out serious diseases such as bowel cancer (colon cancer) or rectal cancer. The stage at diagnosis matters for prognosis and treatment options in cancer of the colon or rectum; the course also depends on tumour factors and your general health.

The symptoms of cancer can resemble those of hemorrhoids or IBD, which is why a visual examination of the inside of the intestine is necessary to make an accurate diagnosis. During an endoscopy, the specialist can also remove polyps. Some types of polyp can develop into cancer over time, so removal forms part of the overall assessment.

How is the examination performed?

When you are referred to us due to blood in your stool, we will typically conduct a thorough interview followed by a clinical examination. Depending on your symptoms and age, a colonoscopy or sigmoidoscopy may be necessary. This allows us to directly view the mucous membrane and take tissue samples if changes are found.

Which examinations are relevant depends on the symptoms, your age, your risk profile and the overall medical assessment.

A review of what the colour of the blood and the accompanying symptoms can point to is available in the article Rectal bleeding: is it haemorrhoids or a sign of bowel cancer?.

Frequently asked questions about blood in stool (FAQ)

Here you will find answers to the most common questions about rectal bleeding. blood in the stool should always be investigated by a doctor to determine the precise cause.

Is it always dangerous to have blood in the stool?

No, in many cases, bleeding is due to benign conditions such as hemorrhoids or small tears (anal fissures). However, since symptoms can overlap with more serious diseases, it is crucial to be examined by a specialist to rule out polyps or bowel cancer.

References:

• Arnold M, Sierra MS, Laversanne M, Soerjomataram I, Jemal A, Bray F (2017). Global patterns and trends in colorectal cancer incidence and mortality. Gut 2017;66(4):683-691. - The study emphasizes the importance of early diagnosis for symptoms such as bleeding to significantly improve prognosis.

• Peery, A. F., et al. (2015). Burden of Gastrointestinal, Liver, and Pancreatic Diseases in the United States. Gastroenterology. - Documents that hemorrhoids and fissures are the most common causes of rectal bleeding in the general population.

What is the difference between bright and dark blood in the stool?

Bright, red blood on the toilet paper or on the outside of the stool typically originates from the lower part of the intestine or the anal opening (e.g., hemorrhoids). Dark or black blood, which is mixed into the stool, may indicate bleeding higher up in the colon or stomach. Both require medical evaluation.

References:

• Lane, S. K., et al. (2004). Evaluation of bloody stools. American Family Physician. - A review of the clinical differences between upper and lower gastrointestinal bleeding based on the color and consistency of the blood.

When should I seek medical attention immediately?

You should contact a doctor as soon as possible, especially if the bleeding is accompanied by altered bowel habits (e.g., persistent diarrhea or constipation), unexplained weight loss, abdominal pain, or if you feel unusually tired (signs of anemia).

References:

• Hamilton, W., et al. (2005). Clinical features of colorectal cancer before diagnosis: a population-based case-control study. British Journal of Cancer. - Identifies "red flag" symptoms, including bleeding combined with altered bowel habits, as strong indicators of bowel cancer.

Can stress cause blood in the stool?

Stress can affect the stomach and bowel and cause pain, bloating and changes in bowel habit, but stress does not in itself explain visible blood. If you see blood in your stool, it should still be assessed by a doctor.

Can you tell yourself if the blood is due to hemorrhoids or cancer?

No, it is impossible to tell the difference yourself. Even if you have previously had hemorrhoids, new bleeding could be due to something else. An endoscopic examination (colonoscopy or sigmoidoscopy) is the examination that inspects the mucous membrane directly and clarifies what the bleeding is caused by.

References:

• Rinesmith, S. E., et al. (2005). Colorectal cancer screening and surveillance. Gastroenterology Nursing. - Explains why visual inspection via endoscopy is the reference standard for distinguishing between benign and malignant changes.

Read more about bowel examination

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Further investigation

Which examination is relevant depends on the appearance of the blood, the accompanying symptoms, age, risk profile and the overall medical assessment. Not everyone with rectal bleeding needs a colonoscopy.

Colonoscopy · Sigmoidoscopy