Colonoscopy: Information for men

Photo of a patient and receptionist
PantherMedia / Tyler Olson

In a colonoscopy, the colon (large intestine) is examined for and areas of abnormal tissue. Polyps that might become cancerous later on can be removed during the colonoscopy. 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 (sometimes also called coloscopy) 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 view 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 them. The tissue sample 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 viewing the walls of the colon. Throughout the procedure, the colon is widened using 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 information

During a colonoscopy

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 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 allows you to sleep so that you will hardly be aware of the examination. 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.

Sometimes a colonoscopy is stopped if it becomes too unpleasant. It's also not always possible to push the far enough into the large intestine because of particular anatomic features. This problem is more common in people who have had abdominal surgery in the past because that can cause tissue to scar and stick together in the abdominal cavity, making the intestinal loops too inflexible.

How reliable are the outcomes of colonoscopies?

In colonoscopies, the entire colon is examined to find and potentially cancerous tissue. Larger colorectal are usually detected. 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 tumors that have already started growing are nearly always found during colonoscopies. It is estimated that 95% of all tumors are discovered in this way.

Do colonoscopies lower the risk of colorectal cancer?

Several studies have looked into the advantages and disadvantages of colonoscopies. The pros and cons depend on various factors, including the age of the person being examined. The following tables show the main results for men over the age of 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 thatout of 1,000 men ... ... death from colorectal canceris prevented in 1 to 3 more men. ... the development of colorectal canceris 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 thatout of 1,000 men ... ... death from colorectal canceris prevented in 3 to 6 more men. ... the development of colorectal canceris 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.

Widening the bowel with air quite often causes temporary side effects such as mild pain or bloating. The sedative or anesthetic used may lead to problems like dizziness or cardiovascular issues.

Overall, complications that require medical treatment occur in about 2 to 3 out of 1,000 colonoscopies. The most common of these is bleeding following the removal of . The bleeding can usually be treated without having to stay in the hospital.

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. This 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 single, small, normal polyp is found, the next colonoscopy can be done ten years later.

But if an abnormal or larger polyp is found, or if more than three 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 is necessary to have a second colonoscopy because it wasn't possible to completely remove a polyp during the first. In Germany, the costs of these examinations are covered by statutory health insurers.

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

Brenner H, Stock C, Hoffmeister M. Effect of screening sigmoidoscopy and screening colonoscopy on colorectal cancer incidence and mortality: systematic review and meta-analysis of randomised controlled trials and observational studies. BMJ 2014; 348: g2467.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Invitation and decision aid for bowel cancer screening: final report; commussion P15-01. October 24, 2016. (IQWiG reports; volume 451).

Lin JS, Piper MA, Perdue LA, Rutter C, Webber EM, O’Connor E et al. Screening for Colorectal Cancer: A Systematic Review for the U.S. Preventive Services Task Force. Rockville (MD): AHRQ, June 2016. (Evidence Syntheses, volume 135).

Neugut AI, Lebwohl B. Colonoscopy vs sigmoidoscopy screening: getting it right. JAMA 2010; 304(4): 461-462.

Pignone M, Rich M, Teutsch SM, Berg AO, Lohr KN. Screening for colorectal cancer in adults at average risk: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2002; 137(2): 132-141.

Robert Koch-Institut (RKI). Krebs in Deutschland 2011/2012. Berlin; 2015.

Zentralinstitut für die kassenärztliche Versorgung in Deutschland (ZI). Wissenschaftliche Begleitung von Früherkennungs-Koloskopien in Deutschland: Berichtszeitraum 2014. Berlin/Cologne; 2016.

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.

Comment on this page

What would you like to share with us?

We welcome any feedback and ideas. We will review, but not publish, your ratings and comments. Your information will of course be treated confidentially. Fields marked with an asterisk (*) are required fields.

Please note that we do not provide individual advice on matters of health. You can read about where to find help and support in Germany in our information “How can I find self-help groups and information centers?

Updated on January 26, 2017
Next planned update: 2021


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

How we keep you informed

Follow us on Twitter or subscribe to our newsletter or newsfeed. You can find all of our films online on YouTube.