How is colon cancer diagnosed?


If colon cancer is suspected, the patient's medical history (anamnese) be collected. Of particular interest are symptoms that are suspicious of tumors as well as the family medical history with possible evidence of an increased incidence of colon cancer. The patient should then be given a thorough physical examination. The most important examination is the palpation of the rectum.


Up to 60% of the tumors can be palpated with a rectal palpation examination. In the case of higher-lying tumors, a tumor mass in the abdomen (abdomen) can be felt.

A haemoccult test is used to search for blood in the stool, which can occur as a result of tumor-related blood loss in the gastrointestinal tract. From the age of 50, this is also recommended for colon cancer screening.

Anyone who has frequent cases of family members who have colon cancer can also have genetic testing carried out in order to better assess their individual risk of developing cancer.

When analyzing the blood (laboratory values), certain blood values ​​can indicate a tumor disease. For example, low blood pigment levels (hemoglobin) indicate chronic blood loss, which can be more common especially with this type of tumor. So-called tumor markers are substances in the blood that are often found in some types of cancer and can thus indicate a cancer. Tumor markers are either formed by the tumors themselves or their formation is stimulated by them. They do not play an essential role in the initial diagnosis of colon cancer, as it is not uncommon for false-positive results to be found (positive tumor marker, but not cancer).

However, if a certain tumor marker value is found to be elevated before an operation, which disappears after the operation, this marker can be used particularly well to prevent a renewed outbreak of the tumor (Tumor recurrence) diagnose with a quick blood test. The final confirmation of the diagnosis is made by a colonoscopy (Colonoscopy) with tissue sampling. Pictures of a colonoscopy can be seen under the topic of colon cancer.

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The colonoscopy is the method of choice for the direct assessment and classification of damage to the mucous membranes and should be carried out if colon cancer is suspected. During this examination, a tube camera (endoscope) Transferring images to a monitor. To do this, the camera is extended to the end of the colon (Cecum) and then, while slowly withdrawing, assess the mucous membrane. During the colonoscopy, tissue samples (biopsy) can be taken from suspicious areas of the mucous membrane.

The reflection is also particularly suitable for larger mucosal growths (Polyps) to be removed with a loop. The tissue assessment under the microscope (histological finding) is far more meaningful than the one seen with the naked eye (macroscopic) Findings. The type of tumor and its spread in the layers of the intestinal wall can only be determined in the histological examination.

This is to be distinguished from the so-called rectoscopy (Recto-sigmoidoscopy). This method enables the lower intestine sections to be viewed (Rectum, rectum and sigmoid colon) by means of a rigid pipe. Since this examination can only see the end of the intestine, it offers no advantages over colonoscopy and is therefore not routinely used in tumor diagnostics.

Read more on the subject at: This is how colon polyps are removed

X-ray swallow

In this non-invasive, imaging examination, the abdomen is X-rayed after the patient has swallowed an X-ray contrast medium. The contrast agent is placed on the intestinal walls so that an assessment is possible. During this examination, for example, the degree of bowel narrowing (Stenosis) can be assessed by the colon cancer, especially if the colonoscopy cannot be performed. However, compared to a colonoscopy, the assessment of changes in the mucous membrane is limited. For this purpose, the direct assessment of the intestinal mucosa by mirroring with tissue removal (biopsy) essential.

How is the tumor stage determined?

Once the diagnosis of colon cancer has been confirmed, the tumor stage is then determined and the further therapeutic approach planned. You judge with different methods

  • the tumor spread (T)
  • the lymph node involvement (N)
  • and possible distant metastases (M).

The usual classification is done with the TNM system.

You may also be interested in this topic:

  • TNM system
  • The course of colon cancer


In an endoscopic ultrasound, as with a colonoscopy (Colonoscopy) also, a flexible tube advanced to the tumor. However, in this examination, an ultrasound head is attached to the end of the hose instead of the camera. With this method, by placing the transducer on the tumor, it can spread in depth (infiltration) the intestinal wall can be made visible and lymph nodes in the vicinity of the intestine are also assessed


With sonography (Ultrasonic) one cannot assess abdominal organs invasively and without radiation exposure. When performing ultrasound of the abdomen (abdomen), for example, metastases in the liver or affected lymph nodes in the abdomen (abdomen) are revealed. Since the method is easy to use and is not stressful for the patient, it can be repeated often and used particularly for follow-up and follow-up care.

Computed Tomography

The spiral computed tomography (Spiral CT) can provide information about the extent of the tumor, about the spatial relationship to neighboring organs, about the lymph node involvement and also about distant metastases. Computed tomography is required from both the chest cavity (thorax) as well as from the abdomen (abdomen) in order to be able to assess all possible ways in which the tumor has spread (especially in the liver and lungs). Magnetic resonance tomography (MRI).

Read more on the subject at: Computed Tomography

Chest x-ray

An overview X-ray of the chest (chest X-ray) can provide information about the involvement of the lungs by metastases.

Read more on the topic: X-ray of the chest