Rectal cancer: definition, signs, therapy

Cancer of the rectum or rectum (rectal cancer) is a malignant tumor that originates in the lining of the lower part of the intestine

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The rectum is at the end of the intestine and opens into the anal canal

© W & B / Ulrike Möhle

Colon Cancer - In Brief

Doctors refer to tumors of the intestine that are less than 16 centimeters from the anus as rectal cancer (rectal cancer). Small carcinomas can be removed endoscopically, while larger ones are operated with an abdominal incision. In addition to surgery, many patients receive a combination of radiation and chemotherapy, but sometimes just radiation therapy.

Definition: what is rectal cancer?

The rectum is the last part of the large intestine and opens into the anal canal. It is about six to eight inches long. According to the international definition, tumors that are 16 centimeters or less from the outer line of the anal canal (anus) are referred to as rectal cancer (rectal cancer, rectal cancer).

Rectal cancer often arises from an initially harmless tissue change in the form of benign growths (polyps). If certain factors are added, these polyps can degenerate and develop into cancer.

Colon cancer (i.e. carcinoma of the colon and rectum) is the third most common cause of cancer-related death in Germany. The annual new cases in Germany in 2014 were around 33,000 in the male and slightly less (around 28,000) in the female population.

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Polyps: Colon cancer can develop from them

© Shutterstock / Juan Gaertner

Causes and Risk Factors

Polyps and inflammatory bowel disease

In most cases, rectal cancer develops from benign tissue changes called polyps. These initially benign growths of the intestinal mucosa can degenerate under certain circumstances. Then the individual cells multiply excessively and in an uncontrolled manner, eventually growing into the surrounding tissue and destroying it. If cancer cells get into the blood and lymph vessels, they can reach other organs in the body and form daughter tumors (metastases) there.

People with many such benign polyps in their intestines have a higher risk of developing colon cancer compared to the rest of the population. Long-standing inflammatory bowel disease (particularly ulcerative colitis) also increases the likelihood of rectal cancer. If, after certain bladder diseases, urinary diversion has to take place via the intestine, this is also a risk factor.

Genetic predisposition

Genetic predisposition can also play an important role. Not everyone with cancer in the family falls ill. However, if one or more first-degree relatives (e.g. parents or siblings) are affected by colon cancer, you have a higher than average risk of cancer. Certain hereditary diseases promote the occurrence of tumors: the two most important are Lynch syndrome or hereditary non-polypoid cancer syndrome (HNPCC) and familial adenomatous polyposis (FAP). A special gene test can clarify whether a person actually has these diseases.


The risk of developing rectal cancer increases with age. Cancer researchers attribute this to the fact that with age, the ability of a person's cells to repair defects in genetic material decreases. If such errors accumulate in the genome, the cells can degenerate. In rare cases (for example, with HNPCC or FAP), rectal cancer develops in middle age. It usually only occurs in the sixth and seventh decades of life.


Long-term smoking and high alcohol consumption can increase the risk of rectal cancer. A healthy diet, on the other hand, has a preventive effect. We recommend an intake of 30 grams of fiber per day. These food components stimulate the intestinal activity and promote digestion. In addition, you should put plenty of vegetables, fruit, whole grain products and legumes (such as lentils, peas and beans) on the menu. Red and processed meat should only be consumed in moderation and alcohol should be avoided if possible. Regular physical activity (at least two and a half hours per week of moderate physical exertion or 75 minutes of intensive training per week), on the other hand, has a preventive effect. Anyone who is overweight should try to shed the extra pounds.

If the test for blood in the stool is positive, a colonoscopy should follow

© W & B / Heller


Signs of rectal cancer are similar to those of benign bowel disease. This means that not every irregularity in the bowel movement always means cancer. Nevertheless, it is advisable to consult a doctor and possibly even a specialist such as a proctologist or gastroenterologist if you have the following symptoms:

• Visible bleeding from the anus

• painful bowel movements

• Change in bowel habits (especially from the age of 40)

• blood in your stool

• Atypical stool discoloration

• Loss of performance and fatigue

• Persistent constipation or intestinal obstruction

• weight loss (rare)

• fever (rare)

Prevention: The colonoscopy helps to detect cancer and its precursors at an early stage

© iStock / robertprzybysz

Colon Cancer Early Detection

In Germany, women aged 50 to 54 have the right to have a blood test in their stool once a year. Men of this age group can take the annual stool test if they decide not to have a colonoscopy. The following applies to both sexes: From the age of 55, the test can be taken every two years as long as no colonoscopy has been taken. A palpation of the lower part of the intestine can be done in men as part of the early detection of prostate cancer. In women, the doctor can perform this examination during gynecological preventive care.

Men from 50 years of age and women from 55 years of age can have a colonoscopy. Men develop colon cancer earlier than women, so the first colonoscopy is recommended for them earlier. A new colonoscopy is then possible at least ten years apart. If the first colonoscopy does not take place until the age of 65 or above, a second colonoscopy is no longer planned.

For people whose cancer runs in their families, earlier preventive examinations (possibly before the age of 45) and / or additional genetic tests may be useful in individual cases.

Palpation examination (rectal examination):

The doctor scans the anal canal and the lower part of the intestine with his finger. With this simple method, he can detect bumps such as polyps or a lump. However, since the examiner's finger only reaches the smallest part of the rectum, rectal cancer cannot be safely ruled out.

Chair test:

A stool sample is examined for blood. With the help of specific antibodies that are directed against human blood components, it is also possible to detect blood that cannot be seen with the naked eye. If the test for blood in the stool is positive, a colonoscopy will help pinpoint the source of the bleeding.


For a colonoscopy, a tube about one and a half meters long with a camera and light source (endoscope) is inserted into the anus. The doctor uses this examination instrument - if possible - to examine the entire large intestine up to the transition to the small intestine. If he notices a tissue change, the doctor can either take a tissue sample with forceps (biopsy) or remove benign growths (polyps) completely with appropriate instruments.

The possibility of virtual colonoscopy has been the subject of much discussion in recent years. For this purpose, a computed tomography is carried out in which cross-sectional images of the large intestine are generated. When placed next to one another, the initially two-dimensional sectional images enable a three-dimensional reconstruction of the intestine to a complete image of a virtual colonoscopy. However, computed tomography is not a standard examination in the context of early detection, but is actually only considered if a complete reflection of the intestine is not possible. There are good reasons for this: Computed tomography is associated with radiation exposure. In addition, suspicious tissue changes cannot be removed and examined immediately.

Video: what is a colonoscopy?