Colonoscopy: Information for men

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In a colonoscopy, the colon (large intestine) is examined for and areas of abnormal tissue. If any are detected, they can be removed immediately. This lowers the risk of . Complications such as bleeding may occur, and there is a small risk of injury to the wall of the colon.

The descriptions found here refer to the health care system in Germany, where all men over the age of 50 can have two free colonoscopies to screen for . If no abnormalities are found in the first colonoscopy, they can have a second one ten years later at the earliest. The reason for the wait is that it takes many years for to develop from colorectal . Those who do not wish to have a second colonoscopy after ten years can have a stool test every two years instead.

Colonoscopies for purposes are generally not recommended for men over 75 because the risk of complications increases with age. A colonoscopy may also be too much for people with certain chronic diseases, such as severe heart failure.

What do colonoscopies involve?

A colonoscopy is an examination of the entire large intestine with a special called a colonoscope. This is a long flexible tube about 1.5 meters long and 1 cm in diameter. The end of the colonoscope has a light attached to it and a tiny video camera so that the doctor can see the inside wall of the bowel. If or abnormal areas of mucous membrane are found during the procedure, they can be removed right away. A small wire loop or forceps can be pushed through the colonoscope and used to remove the tissue, which is then examined more closely in a laboratory.

The colonoscope is inserted into the anus and pushed up to where the small and large intestine meet (roughly where the appendix is, as in the illustration). The doctor then slowly pulls the colonoscope out while looking at the walls of the colon. Throughout the procedure, the colon is inflated with air or carbon dioxide to make it easier for the doctor to see the walls of the bowel.

Illustration: During a colonoscopy – as described in the article

How can you prepare for a colonoscopy?

Before having a colonoscopy, you will have a doctor's appointment to discuss the procedure and how to prepare for it. Your entire large intestine has to be as empty as possible for the examination. Depending on what time of day it is carried out, you will take a laxative with two to four liters of fluids the evening before and/or on the morning of the procedure. You can drink water, broth, tea or juice. You are not supposed to eat any solid foods from two to three hours before taking the laxative until after the colonoscopy. After cleansing your colon in this way, only a clear liquid should come out when you go to the toilet.

It is usually possible to eat again right afterwards. If larger were removed it may be a good idea to wait a while, though.

You will be offered a sedative before the colonoscopy. This causes you to fall asleep for a short while and makes the examination less unpleasant. If you take a sedative you should not drive or operate any machinery for the next 24 hours. The examination takes about 15 to 45 minutes.

It is usually possible to push the colonoscope up to the appendix to view the entire large intestine. Sometimes the colonoscopy needs to be stopped because it's too unpleasant or because the colonoscope can't be pushed far enough. That may be due to abnormal anatomical features, scars or growths in the abdominal cavity. This problem is more likely in people who have had abdominal surgery in the past.

How reliable are the outcomes of colonoscopies?

In colonoscopies, the entire colon is examined to find and potentially cancerous tissue. Larger colorectal are usually discovered that way. But even colonoscopies don't offer complete protection against . Some abnormalities may be overlooked, especially small or flat that are harder to see. It also isn't always possible to fully cleanse the bowel before the examination. Then it's more difficult to get a clear view of the walls of the bowel.

Any cancer that has already started growing is nearly always found during colonoscopies, though. It is estimated that 95% of all colorectal cancers are discovered in this way.

Do colonoscopies lower the risk of colorectal cancer?

Several studies have looked into the pros and cons of colonoscopies. These depend on various factors, including the age of the person being examined. The following tables show the main results for 55-year-old men and for 65-year-old men. Each table describes what could happen within a period of ten years after having one colonoscopy.

Out of 1,000 men who are 55 years old ...
  ... will die of . ... will develop . ... will have complications.
Without 4 13 0
With a colonoscopy 1 to 3 4 to 10 2
This means that out of 1,000 men ... ... death from is prevented in 1 to 3 more men. ... the development of is prevented in a further 3 to 9 men. ... 2 men will have complications.
Out of 1,000 men who are 65 years old ...
  ... will die of . ... will develop . ... will have complications.
Without 9 24 0
With a colonoscopy 3 to 6 8 to 20 3
This means that out of 1,000 men ... ... death from is prevented in 3 to 6 more men. ... the development of is prevented in a further 4 to 16 men. ... 3 men will have complications.

What are the possible risks and side effects of a colonoscopy?

Colonoscopy is the examination for that takes the most time and effort. Preparing for it – drinking large amounts of fluid and completely emptying your bowels – can be unpleasant and bothersome.

Inflating the bowel with air sometimes causes temporary problems such as pain or bloating. The sedative or anesthetic used may lead to problems like dizziness or cardiovascular issues.

In about 2 to 3 out of 1,000 men, colonoscopies lead to complications that need to be treated. The most common of these is bleeding caused by the removal of . The bleeding can usually be treated well in an outpatient setting.

In fewer than 1 out of 1,000 colonoscopies, cardiovascular problems or bowel perforations that require treatment occur. The bowel may become perforated if the tip of the colonoscope is pushed against the wall of the bowel with too much force, or if the wall of the bowel is injured when a polyp is removed. A bowel perforation can be life-threatening and immediate surgery is needed.

What happens if polyps are found?

Polyps are discovered in nearly half of all men who have a colonoscopy. If only a few, small are found, and they're not considered to be abnormal, the next endoscopy can be done ten years later.

But if several, abnormal or larger are removed during the procedure, there is a greater risk of more developing in the next few years. If that happens, doctors recommend having the next colonoscopy in three to five years. In rare cases it's necessary to have a second colonoscopy because it wasn't possible to completely remove a polyp during the first. In Germany, the statutory health insurers cover the costs of any further examinations that are needed.

Because it's not possible to predict which will become cancerous and which won't, many "harmless" will be removed too. But that is an inevitable consequence of .

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Invitation and decision aid for bowel cancer screening: final report; commussion P15-01. 2016.

Jodal HC, Helsingen LM, Anderson JC et al. Colorectal cancer screening with faecal testing, sigmoidoscopy or colonoscopy: a systematic review and network meta-analysis. BMJ Open 2019; 9(10): e032773.

Lin JS, Perdue LA, Henrikson NB et al. Screening for Colorectal Cancer: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA 2021; 325(19): 1978-1997.

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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