Signs of colorectal cancer

Photo of a woman with abdominal pain

Colorectal (bowel) cancer doesn't cause any symptoms at first and often goes undetected until it has reached a later stage. Certain symptoms may be signs of , but they are usually caused by another, non-cancerous condition.

Colorectal (bowel) cancer doesn't cause any symptoms at first and often goes undetected until it has reached a later stage. Certain problems may be a sign of , but they are usually caused by something else.

Possible signs of include:

  • Blood in stool (reddish, black or very dark stool)
  • Bleeding or secreting mucus (slime) from your bottom
  • Change in bowel movements over several weeks (for example constipation or diarrhea, sometimes alternating)
  • The feeling of not being able to empty your bowels properly
  • Pains or cramps in the abdomen (belly) or around the anus
  • Unintentional weight loss
  • Tiredness and physical weakness

All of these symptoms are non-specific. In other words, they could also be caused by other diseases such as irritable bowel syndrome (IBS), inflammation of the lining of the stomach (gastritis), a peptic , a food intolerance, or an inflammatory bowel disease. Bowel cancer is very rarely the cause of these problems, especially in people under the age of 40.

Adelstein BA, Macaskill P, Chan SF et al. Most bowel cancer symptoms do not indicate colorectal cancer and polyps: a systematic review. BMC Gastroenterol 2011; 11: 65.

Del Giudice ME, Vella ET, Hey A et al. Systematic review of clinical features of suspected colorectal cancer in primary care. Can Fam Physician 2014; 60(8): e405-415.

Jellema P, van der Windt DA, Bruinvels DJ et al. Value of symptoms and additional diagnostic tests for colorectal cancer in primary care: systematic review and meta-analysis. BMJ 2010; 340: c1269.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on September 13, 2021

Next planned update: 2024


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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