Colon carcinoma (cancer of the large intestine), symptoms and complaints

Cancer in the colon can manifest itself in different ways, depending on where in the colon the tumor is located and how large it is.

Last updated: 29. Oct. 2019

Last revised: 27. Apr. 2017

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What is colon cancer?

There are two main types of cancer in the colon: rectal cancer, in the last ca. 15 cm of the colon, and colon cancer in the remaining parts of the colon. In technical language, one speaks of rectal carcinoma (rectum) and colon carcinoma, more generally also of colorectal carcinoma.

Colon, general view

Most cases with colon cancer start with small, benign structures called adenomatous polyps. Over time, some of these polyps grow, change character, and develop into malignant tumors (cancer).

Polyps are often small and cause few or no symptoms.

Symptoms and symptoms

Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms do occur, they vary depending on the size of the tumor and where in the intestine it is located. Often the tumor grows slowly.

Symptoms and symptoms of colon carcinoma can be:

  • Changes in bowel movements in the form of diarrhea (diarrhea) or constipation (constipation) or a change in the consistency of the feces
  • Bleeding from the rectum or visible blood in the stool
  • Persistent discomfort in the colon, such as pain, gas, or cramping
  • A feeling that the bowels can never be completely emptied.
  • unexplained weight loss.


When intestinal cells bleed, the blood may mix heavily with the stool and therefore not be noticeable. Therefore, such bleeding may occur unnoticed and last for a long time. Anemia develops from the constant loss of blood due to the loss of iron. You feel tired and have pale skin. The carcinoma can often, but not always, be detected by a stool examination for hidden (occult) blood. There is a test for this that you should do at home on 3 days (3 bowel movements). If only one stool sample is examined, the result is very uncertain. You may also be asked to collect stool samples in a container given to you by your doctor. The samples are then examined using an even more detailed test.

Narrowing in the intestine, stenosis

If the tumor has become quite large, it can completely or partially block the colon – a stenosis develops. If there are passenger difficulties, the following symptoms will occur:

  • Large stomach without gaining weight.
  • stomach pain, which is rare in colon carcinoma.
  • unexplained, persistent nausea and vomiting
  • conspicuous, small amounts during bowel movements
  • The feeling that the bowel has not been completely emptied during defecation.
  • Rectal pain: pain is rare in colon cancer, but it can be a sign that a tumor is growing in the surrounding tissue.

Tumors in the right or. Left part of the colon

Symptoms appear late, especially if the tumor is located in the right half of the colon. It is either caused by bleeding from the tumor in the intestine or manifests as narrowing because the intestine is blocked where the tumor is located. On the right side, the colon is wider and the tumor can often grow for a long time without causing noticeable narrowing or symptoms. The opposite is true on the left side: the closer the tumor is to the rectum, the earlier symptoms appear, such as changes in bowel movements, the feeling of incomplete emptying, evtl. Blood (red) or mucus in the stool and pain during bowel movements.

Colon carcinoma, tumor in the lower part of the intestine
Colon cancer, narrowing in the bowel

More than half of patients with colorectal carcinoma have noticed blood in the stool. This is especially common when the tumor is located in the lower part (left side) of the colon. The higher up the tumor is in the intestine, the more often blood mixes with the intestinal contents and is difficult to detect. Anemia is evident with falling blood levels (Hb) and increasing fatigue. If the Hb value decreases by 1-2% within one year in persons with stable blood values, the colon should be examined for carcinoma.

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