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Diagnostics > Colonoscopy

Colonoscopies: 12 questions you need to answer

Dr. med. André Sommer

Dr. med. André Sommer

A colonoscopy examines the colon, and it plays an important role in the prevention of colon cancer and in the diagnosis of other diseases such as inflammatory bowel disease. The examination is carried out by a doctor who inserts a device (colonoscope) through the anus into the intestine and takes pictures of the intestinal mucosa. Before a colonoscopy, the patient has to “cleanse” with laxatives so the doctor can assess the intestine from the inside.

Important information about colonoscopies at a glance:

  • A colonoscopy is a central component of colorectal cancer screening.
  • Regular colonoscopy checks can effectively reduce the risk of colon cancer.
  • A regular colonoscopy is also part of the standard diagnosis for inflammatory bowel diseases.
  • The cost of a colonoscopy for colon cancer screening every ten years is taken over by the health insurance company starting at the age of 55.
  • Alternatives to a colonoscopy are often less meaningful or are only paid for by health insurance companies in certain cases.

When is a colonoscopy performed?

There are various situations in which a colonoscopy can be medically recommended. For example:

  • If relatives have had colon cancer, the first colonoscopy is recommended either from the age of 40-45 or at least ten years before the earliest instance of cancer in the family.
  • If there are familial tumor syndromes that put one at high risk of colon cancer. These include familial adenomatous polyposis (FAP) or hereditary, non-polypous colon carcinoma syndrome (HNPCC). There are special tumor prevention programs for those affected, with more frequent colonoscopic examinations.
  • A colonoscopy is often offered for further clarification to patients with chronic inflammatory bowel diseases or suspected of such or patients with unusual, persistent indigestion or blood in the stool.
  • Patients with already diagnosed ulcerative colitis have an increased risk of colon cancer. They therefore receive regular colonoscopies. The frequency depends on the severity and extent of the inflammation. Similar standards apply to Crohn's disease, although there is no increased risk of colorectal cancer for Crohn's disease patients.
  • If there is a history of colorectal cancer, regular follow-up colonoscopies are part of the aftercare program.
  • Irritable bowel syndromes do not increase the risk of colon cancer. In the clarification of functional digestive complaints, however, a colonoscopy is usually performed to find possible causes of the digestive complaints.

How do I prepare for a colonoscopy?

Before the colonoscopy, medical advice is given with information about the examination and the necessary preparatory measures. The doctor must be informed about all medications that are taken regularly.

The colon must be completely empty before the colonoscopy. Otherwise, the examiner cannot assess the intestinal mucosa or can only assess it incompletely. To do this, the patient must follow the examiner's instructions for colon cleansing. The recommendations may vary slightly from examiner to examiner. Generally, no food containing grains or swelling agents should be taken from about four days before the examination. This also includes grain-containing fruits such as kiwi and some berries. No solid food may be consumed starting from noon the day before the examination. Clear liquids can be drunk or spooned as broth.

The evening before the examination, a liquid laxative (e.g. “Mivoprep”) is drunk and a lot of clear liquid is still drunk. The doctor will inform the patient about the laxative they should take. Increased bowel movements can start overnight.

Also in the morning before the examination, the laxative and a lot of clear liquid are taken again. The bowel movements should then gradually change to a clear, yellowish liquid.

The examination itself can be carried out on an outpatient basis. After colon cleansing, the colonoscopy can be performed.

What happens during a colonoscopy?

The duration of the colonoscopy is usually 15-30 minutes. If the examination conditions are poor or if there are any abnormalities, the examination may take longer. A colonoscopy is often performed on an outpatient basis in a practice (internist, gastroenterologist) or as an inpatient in a hospital.

1. Preparation for the colonoscopy

At the beginning of the examination, the patient lies on their left side in a bed. If desired, a sedative can be given before the examination, which can make the examination more comfortable for the patient. An IV is placed immediately before the examination. A short-acting anesthetic is administered via the IV shortly before the start of the colonoscopy, so you hardly notice the procedure. This makes the examination more pleasant. It also relaxes muscles, which makes it easier for the examiner and increases the meaningfulness of the results.

2. Start of the colonoscopy

The patient lies on their side on the examination table. The examiner will insert the examination tube (an endoscope) using petroleum jelly or a similar lubricant. The tube is about 1.5 m long, with a camera at its end. In addition to the camera, it also offers a “working channel” through which instruments can be guided into the intestine at the end of the tube.

The tube is pushed up to the transition into the small intestine and gas is led into the intestine (air or carbon dioxide) so that it can be better examined from the inside. The examiner slowly pulls the tube back and looks closely at the intestinal mucosa.

Small inflammatory mucosal lesions or small mucosal growths (polyps) for example may be suspicious. Colon cancer almost always develops from polyps that degenerate into malignant tissue over many years. The examiner removes polyps with the help of instruments that they introduce via the working channel. The ablated tissue is then examined histologically.

3. End of colonoscopy

The exam is over after about 30 minutes. The patient can rest a little and should then be brought home by a friend. Driving is not possible for 24 hours after the examination because the sedative is still working.

4. After the colonoscopy

During the examination, the colon is inflated with air through the endoscope in order to improve the viewing conditions. The remaining air can cause abdominal pain after the examination and lead to increased flatulence. After the examination, it is important to let the air out of the intestine to prevent abdominal pain. An alternative to using air to inflate the intestine is to use carbon dioxide. The advantage is that carbon dioxide is absorbed much better through the intestinal mucosa and less abdominal pain and bloating occur after the examination.

When can you eat again after a colonoscopy?

Post-examination and after the sedative medication has subsided, the patient is allowed to eat and drink as normal.

When should another colonoscopy be performed?

The results of the investigation are communicated in a debriefing and any consequences are discussed. In normal colorectal cancer screening, the next control colonoscopy is carried out after around ten years.

Why get a colonoscopy?

Colonoscopies are primarily used for colorectal cancer screening and for diagnosing chronic inflammatory bowel diseases. Colon cancer arises from intestinal mucosal polyps. Polyps are benign overgrowths of the intestinal mucosa, some of which can develop into malignant colon cancer over time. The polyps are removed during a colonoscopy - so the colorectal cancer precursors are removed. If colon cancer has already developed, colonoscopy will detect it before it shows any symptoms. The earlier the cancer is discovered, the better the treatment options.

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What alternatives are there to a colonoscopy?

Many patients want to avoid colonoscopies because the examination can be uncomfortable. If patients reject colon cancer screening using colonoscopy, a test for blood in the stool or a colonoscopy of the rectum and sigmoid (the posterior sections of the intestine) can be performed. The entire intestine is not assessed, so the results are less useful.

Other alternatives are video capsule endoscopy and MRI or CT-assisted colonoscopy. With video capsule endoscopy, a small capsule with an integrated camera is swallowed, which takes pictures of the entire digestive tract and is finally excreted. The images are then evaluated.

It should be noted that intestinal cleansing using laxatives is also required for both of the alternatives mentioned. If polyps are discovered, a colonoscopy is required, as otherwise the polyps cannot be removed.

Which doctors perform colonoscopies?

Colonoscopies are performed by gastroenterologists (specialists in internal medicine with a focus on gastroenterology). There are practices in which colonoscopies are offered. Sometimes, colonoscopies are also carried out during an inpatient stay if acute complaints have led to an inpatient admission.

What risks are associated with a colonoscopy?

A colonoscopy is a low-risk examination procedure. Complications are very rare. Before the colonoscopy, the doctor provides information about the procedure and the possible risks of colonoscopy. The complication rate in therapeutic colonoscopy is 0.4 percent (four complications in 1,000 treatments).

Before the exam, it is important to tell the doctor if you are taking blood thinning medication, if you are pregnant, or if you have a heart/lung disease. The doctor should also be informed about allergies to certain medications and foods (e.g. soy). If there has been a gastric or intestinal perforation in the past, this should also be reported.

The most common risks of colonoscopy are:

1. Bleeding from injury to the intestinal wall

The risk is 0.3 percent (three cases in 1,000 examinations). The risk is increased in patients taking blood thinning medication. It is therefore particularly important to clarify which medications are being taken. Bleeding from the intestinal polyps can also occur.

2. Perforation of the intestinal wall by the endoscope tube

The risk of an intestinal breakthrough (perforation) is 0.06 percent (6 cases in 10,000 examinations). Since the tip of the endoscope is very thin and flexible and the optics are now very small, perforation is extremely rare. The risk of perforation increases due to inflammation of the intestinal tract, as is often the case with inflammatory bowel diseases, for example. Here, the intestinal wall is particularly sensitive due to the inflammation and tears faster than in healthy people.

3. Allergic reaction from the sedative (anesthetic)

It is important to clarify existing allergies in consultation with the doctor. An existing allergy to anesthetics is particularly important.

4. Circulatory problems caused by the sedative (anesthetic)

There is a slowdown in breathing and a drop in blood pressure. Existing heart/lung diseases should be mentioned in consultation with the doctor.

Is a colonoscopy painful?

Many patients find colonoscopies uncomfortable, and some also experience pain. If you want to avoid this, you can ask the doctor for a sedative or pain reliever. On special request, the colonoscopy can also be performed without anesthesia. The doctor and patient make the decision in the preliminary consultation depending on the patient's state of health.

Short-acting anesthesia is also possible, but should only be used if the patient is very afraid. After all, anesthesia is associated with risks. A short-acting anesthetic (often propofol) is administered shortly before the examination via a vein. The effect occurs within one minute and lasts for about two to five minutes because the drug is quickly broken down. Most patients are unaware of the examination.

Which diseases can be recognized with a colonoscopy?

During the examination, the doctor examines the intestinal mucosa of the different sections of the intestine. In addition, photos of the various intestinal areas are taken for documentation purposes. The examiner pays special attention to narrowing of the intestine (stenoses), which can provide an indication of a tumor. In addition, pathological changes in the intestinal mucosa can be identified, such as

  • Deep defects of the intestinal mucosa (ulcers)
  • Cracks in the mucous membrane (fissures)
  • Bleeding of the mucous membrane
  • Reddish inflamed mucous membrane, which can be the result of a chronic inflammatory bowel disease.
  • Colon polyps, which are relatively common, are examined and removed
  • Bulges of the intestinal wall (diverticula), which can become inflamed

The samples obtained using the biopsy forceps are examined for signs of inflammation. Characteristic changes can be found in inflammatory bowel diseases or microscopic colitis. With IBS, there are no typical inflammatory changes in the tissue samples. Instead, the tissue samples taken are used to rule out other diseases so that the IBS diagnosis can be made.

Is it possible to examine the small intestine?

The small intestine cannot be easily reached with the endoscope as part of a regular colonoscopy. A camera capsule (capsule endoscope) is therefore often swallowed to assess the small intestine. Alternatively, so-called balloon enteroscopy and push enteroscopy are available. The camera capsule is only slightly larger than a medication capsule (minimally invasive procedure) and has been in clinical use since 2001. This passes through the intestinal system including the small intestine. Images are captured twice per second using an LED flash of light. The images can then be evaluated. For this purpose, the recordings are transmitted to a storage device by radio. The examination of the small intestine is primarily used to search for bleeding sources, tumors of the small intestine and to diagnose Crohn's disease.

Before examining the small intestine, possible sources of bleeding in other parts of the intestine can be excluded using a regular colonoscopy or an upper endoscopy (esophagogastroduodenoscopy, which examines the esophagus, stomach, and duodenum for changes). This examination method plays a subordinate role in the diagnosis of IBS. A breath test is more likely to be used to investigate a possible colonization of the small intestine.

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Dr. med. André Sommer

Dr. med. André Sommer

I’m André, a medical doctor from Berlin. Together with a team of medical doctors, nutritionists and data scientists we empower people to understand digestive issues with our app Cara Care.

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