Colonoscopy (examination): what it is, what it is for and risks. It hurts?


What is Colonoscopy?

Colonoscopy is an examination that consists of visualizing the interior of the large intestine and the final part of the small intestine, in color images that can be recorded. Made through an endoscope inserted through the anus, it helps to check for lesions in the intestinal walls.

This procedure makes it possible to prevent intestinal cancer , as it is able to remove polyps and stop small bleeds in the colon walls. It can also be used to remove samples of suspicious lesions that are sent for analysis (biopsy).

The examination is performed through an endoscope called a colonoscope. The device passes through the rectum and through the large intestine, until it reaches the distal portion of the ileum, that is, the final part of the small intestine. This colonoscope has a camera at the tip, which shows the inside of the organ on a TV, where the doctor can examine the condition of the intestinal walls.

In general, the exam is performed under sedation and local anesthesia. Thus, it ensures that the patient does not experience discomfort during the process, in addition to making him more collaborative. It is a safe procedure that does not require hospitalization, in most cases.

The doctor who specializes in this test is called a colonoscopist. Other professionals qualified to perform it are endoscopists and coloproctologists. The gastroenterologist is the doctor responsible for the report.

What is virtual colonoscopy?

A variation of the exam is virtual colonoscopy, usually performed when there are difficulties with the traditional environment. This version consists of using computed tomography to obtain images of the interior of the colon. This is a less invasive way to perform the exam, as the tube inserted into the anus does not travel throughout the intestine, being reserved for the final portion of the same, where it injects air to separate the intestinal loops and ensure better visualization. Thus, the procedure has limitations, such as the difficulty in identifying small polyps and the impossibility of extracting suspicious tissues for biopsy.

What is colonoscopy for?

Colon endoscopic examination is often used to prevent intestinal cancer in people over 50. In this case, it is recommended to perform a colonoscopy every 10 years or, if there is a family history of cancer, in an interval of 3 to 5 years.

In younger people, the exam can be ordered in case of:

  • Abdominal pains of unknown cause;
  • Intestinal bleeding;
  • Diarrhea or chronic constipation;
  • Examination of occult blood in the stool with a positive result;
  • Investigation of iron deficiency anemia;
  • Suspected colon cancer;
  • Confirmation of abnormal results in non-invasive exams, such as radiographs, CT scans and ultrasounds;
  • Follow-up of patients who had previously removed polyps.

In the presence of polyps, the colonoscope is able to remove them totally or partially. He can also take samples to biopsy suspicious lesions.

Exam preparation

The preparation for colonoscopy can be quite unpleasant for some patients, since it consists of a special diet and the use of laxative medications.

For the colonoscopist to be able to visualize the intestinal mucosa without interference, it is necessary to clean the colon. Therefore, the doctor must deliver a kit with instructions on how to do this. In general, this process is done at home and presents no danger.

The patient should be on a liquid diet, low in fiber and fat, for about 1 to 3 days before the exam. During this period, laxative medications should be taken to speed up emptying of the colon. It is possible that the doctor prescribes a stronger laxative to be taken especially on the last day before the test.

The diarrhea caused by medications can be unpleasant for the patient, but must take place to ensure that there are no remains of feces in the intestine during a colonoscopy. Ideally, the patient should reserve those days before the exam at home, as he will need to go to the bathroom frequently.

Drinking fluids is essential during these days, as diarrhea causes dehydration. The patient can drink strained fruit juices (except juices with a reddish color, such as grape or strawberry juice ), teas and pure coffee, but the most important is water. You should not drink milk, soft drinks, alcoholic beverages and any reddish colored liquids.

The doctor in charge can pass other instructions for specific cases.

Always remember to check the instructions and clear your doubts with the doctor.

The patient should also ask a friend or family member to accompany him / her on the day of the exam, as the sedation effect may take time to pass.

Do I need to stop taking medications before colonoscopy?

Most medications do not present problems or obstacles for the exam and, therefore, there is no need for discontinuation. It is extremely important that the patient tells the doctor all the medications he uses, so that the necessary adjustments can be made.

Medicines like insulin can be readjusted, especially due to the limited diet that alters the blood glucose level. Iron-based drugs should be discontinued, as they can hinder visualization.

Regarding drugs that act on clotting, there is a need for extra attention. During the examination, the doctor may remove polyps and lesion samples, which causes wounds that can bleed. Anticoagulant medications, such as heparin and warfarin , are contraindicated in patients who will undergo the test. Drugs such as acetylsalicylic acid , clopidogrel and anti-inflammatory drugs do not need to be stopped before the test.

How is the exam performed?

The procedure begins with sedation of the patient, who is placed on his side on a stretcher. In general, this sedation is accompanied by local anesthesia, so that the patient does not feel discomfort during the process.

When the patient is properly sedated, the doctor introduces the colonoscope through the anus. The device injects carbon dioxide to inflate the intestinal loops and open the passage. Thus, it progresses slowly through the rectum and colon, until it reaches the end of the small intestine.

If the doctor finds polyps or suspicious lesions on the way, he can remove them, in addition to collecting material for biopsy, which may take a few days to deliver an official report.

In general, this process lasts between 20 minutes and 1 hour. The effect of sedation, on the other hand, can take a long time to pass, so that there may be somnolence during the rest of the day. Thus, when the examination is over, the patient should not drive, work or operate machinery. Therefore, he should only be released from the hospital or clinic in the presence of a companion.

Does colonoscopy hurt?

Because it is an examination done while the patient is sedated and anesthetized, it is unusual for him to feel any pain during the procedure. However, it is worth remembering that the colonoscope releases carbon dioxide into the intestine, which can lead the patient to colic and the need to release flatus (fart) for some time after the exam.

Can pregnant women do colonoscopy?

Although colonoscopy is an examination of the intestine, it can pose risks to the fetus and is therefore  not suitable for pregnant women , especially in the third trimester.

During advanced pregnancy, colonoscopy may be hampered due to the compression of the colon caused by the enlarged uterus. Complications that can occur during this test (such as intestinal perforation, for example) can lead to uterine trauma. In addition, it is uncertain whether the medications used to cleanse the colon and anesthetize the patient are safe for the developing fetus.

If you are pregnant and need a test to check your colon’s health, your doctor may order a rectosigmoidoscopy as an alternative, an endoscopic test that is not associated with fetal malformations or premature labor induction.


The results of the examination must be evaluated by a gastroenterologist or coloproctologist, who can classify it as normal, abnormal or inconclusive. Find out more below:

Normal (or negative) result

When no abnormality is found in the intestinal walls, the result will be considered normal. If you don’t have any other risk factors – other than age – to develop intestinal cancer, your doctor will probably ask you to repeat the test in 10 years.

Abnormal (or positive) result

The result is considered abnormal when, during the examination, polyps or suspicious lesions were found inside the colon, such as hemorrhoids, ulcers, diverticula or inflammation.

Although most polyps do not represent major risks, some can become precancerous lesions, that is, with great chances of progressing to a malignant neoplasm. The tissues collected during the procedure are sent for analysis.

If the doctor finds few polyps smaller than one centimeter in diameter, it is not necessary to perform a new colonoscopy for about 10 years. However, when the size exceeds 1 centimeter and the amount is large, the doctor may ask you to re-perform the test in 3 or 5 years, depending on the risk factors involved.

When one or more cancerous polyps are removed, the doctor may order follow-up and repeat the exam in about 3 months.

If you have polyps or abnormal tissues that were not removed during the exam, your doctor may recommend that you have a new exam with another doctor who has more experience in removing large polyps.


If the doctor has doubts about the quality of the visualization, or when there are fecal residues that make part of the exam impossible, it may be necessary to repeat it in a short time. When there is also a block that prevents the colonoscope from advancing, the doctor will recommend a virtual colonoscopy.

What can affect the results?

Some normal everyday actions can show changes in the exam images, which can confuse the doctor and deliver an inaccurate report. Are they:

  • Do a barium enema less than a week before colonoscopy;
  • Do not prepare correctly before the exam;
  • Have many turns (sprains) in the colon;
  • Surgeries performed on site;
  • Feeling a lot of pain during the exam;
  • Use iron supplements, which make stools dark and make intestinal cleaning difficult;
  • Eating or drinking food with a red or purple color, such as grape juice and strawberry jam.

After the exam

After the procedure, the patient is under observation for an average of 30 minutes. After that time, if he does not present any major difficulties, he is released to go home accompanied by a family member or caregiver.

It is common to have cramps and release flatus in the hours that the exam is performed. To help release the gases , it is recommended that the patient walk, with the help of a companion.

The effect of sedation can take a long time to pass. Therefore, one should not go home unattended, drive or operate machinery. It is important that the patient, when leaving the hospital or clinic, is at rest and does not do activities that require a lot of effort or care for the body, as the reflexes may be slightly altered for the rest of the day.

In general, the patient can return to eating normally after the examination. Sometimes, as in the case of extraction of polyps and other procedures that can hurt the intestinal walls, the doctor may go on a special diet until the intestine is recovered.

If the patient does not have a family history of intestinal cancer, he will need to undergo the test again after 10 years. When there is a family history, it is recommended to return every 3 or 5 years.


Colonoscopy should definitely not be performed if:

  • Suspected acute abdomen;
  • Suspected acute diverticulitis;
  • Suspected toxic megacolon.

There are also relative contraindications, that is, it is up to the doctor to decide whether to have a colonoscopy or not. In such cases, the advantages and disadvantages must be carefully considered, and the examination must be done cautiously. Are they:

  • Recent myocardial infarction;
  • Recent pulmonary embolism;
  • Neutropenia significativa;
  • Third trimester of pregnancy;
  • Aortic aneurysm;
  • Splenomegaly

If the patient is undergoing treatment with anticoagulants, the examination should be postponed to another occasion.

Complications and risks

Since colonoscopy is a safe test, complications appear very rarely, but they can take on serious proportions. In a normal procedure, the risk of any complications is very low. In the procedures that involve the removal of polyps and biopsies, the risk goes up a little, but the mortality rate remains extremely low (0.007%).

With the removal of polyps and other foreign tissues, there may be bleeding that does not stop on its own. In such cases, you should contact the doctor, who, in general, is able to solve the problem with ease.

More rarely, perforation of the intestine occurs. The patient is submitted to surgery to solve the problem.

Side effects of laxative drugs or sedation are more common. These can be easily circumvented with the help of other medications indicated by the doctor.

Sometimes, it may happen that the patient has prolonged sedation, that is, he remains unconscious for longer than expected. Usually, the doctor is able to resolve this in the exam room itself.

Diseases can hardly be transmitted, since the device is usually sterilized after each procedure.

The patient should contact the doctor if he / she has the following symptoms after the exam:

  • Severe abdominal pain, not being cramps caused by gases;
  • Distension of the abdomen;
  • Vomiting;
  • Fever;
  • Persistent or large bleeding in the stool.

Colonoscopy is a simple test that can help prevent intestinal cancer, as well as catching it early on, increasing the chances of a cure. This article seeks to inform the patient about the procedure, which is safe and rarely presents complications.

If you or someone you know is concerned about colonoscopy, share this article so that more people can understand it better and even avoid future illnesses.