Colonoscopy Exam - Preparation, Sedation and Risks

Colonoscopy is a safe endoscopic procedure that provides information that common radiological tests may not be able to give. Colonoscopy has the advantage that it can be used both for diagnostic purposes and for treatment of some diseases affecting the colon and rectum.

Patients who need to undergo colonoscopy often have many questions and concerns about the procedure. In this text we will explain everything you need to know before undergoing a colonoscopy examination.


What is colonoscopy?

Colonoscopy procedure
Colonoscopy procedure
A colonoscopy is an examination whose goal is to allow the doctor to look directly into the colon (large intestine). To do this, we use an endoscopic device called a colonoscope.

The colonoscope is a long and thin flexible tube, with a length that can reach up to approximately 185 cm and a diameter that varies between 1.0 and 1.3 cm.

Colonoscopy is done by introducing the colonoscope through the anus and progressing it to the beginning of the colon and the end of the small intestine.

At the end of the colonoscope is a microcamera that transmits the images to a monitor, allowing the doctor to see and record what occurs inside the large intestine. The last centimeters of the colonoscope are articulated and can rotate at various angles to facilitate visualization of the entire interior of the colon.

The colonoscope also allows the doctor to introduce a kind of tweezers, which can be used to remove, completely or partially, suspicious lesions, such as polyps.

Rectosigmoidoscopy is a variation of the traditional colonoscopy, being made with a shorter apparatus, which only goes to the end of the descending colon (yellow segment in the illustration above). Retrosigmoidoscopy allows the visualization of the rectum, sigmoid and descending colon, which are the regions of the intestine that most often present tumor lesions.

Reasons for having a colonoscopy

Because colonoscopy allows direct visualization of the interior of the intestine, it is usually indicated as a diagnostic medium for a variety of conditions of the intestinal tract. The most common reasons for staging a colonoscopy are:
  • Screening for colon cancer
  • Investigation of intestinal bleeding
  • Investigation of changes in bowel habits, such as persistent diarrhea
  • Investigation of anemia due to iron deficiency
  • As a follow-up examination of people with intestinal polyps
  • Investigation of chronic abdominal pain with no apparent cause
  • Confirmation of abnormal results on non-invasive examinations, such as x-rays, CT or ultrasonography

How is the preparation for colonoscopy

Before colonoscopy, the colon must be completely cleaned so that the doctor can see the mucous of the colon without interference. Most patients find the preparation more unpleasant than the actual exam.

Your doctor should give you specific instructions on how to prepare for the colonoscopy. It is common to receive a kit with instructions on how to proceed. Be sure to read the instructions in advance so that you can get in touch with your doctor in a timely manner should you have any questions.

Preparation begins with a solid food free diet for 1 to 3 days. To clean the colon, it is customary to use a strong laxative to take the night before the examination. Some doctors also indicate performing an enema to aid in cleansing. The goal is to even cause a severe diarrhea, so that not on remains of feces in the colon, able to disrupt the colonoscopy. Do not schedule anything out of the house on the eve of the exam. You will have a lot of diarrhea, needing to go to the bathroom often to evacuate.

It is important that you drink plenty of fluids the day before. The most indicated are:
  • Strained fruit juice
  • Water
  • Pure coffee
  • Common tea
  • Sports drinks, like Gatorade
  • Gelatine

Avoid soda, milk, or any reddish-colored liquid.

Should i stop taking my usual remedies before the colonoscopy?

You should tell your doctor all the medicines you take so that he can know if there are any drugs that should be stopped before the colonoscopy. Most medications do not need to be stopped before the test, but some dosages may need adjustment, as in the case of diabetes medications, because of decreased food intake before the procedure. It is also important to tell your doctor about the use of iron-based medications, as these can disrupt the visualization of the colon.

Drugs that act on clotting are the ones that should receive more attention, since the doctor may choose to take small samples of intestinal tissue during the colonoscopy. Usually, aspirin, clopidogrel, and anti-inflammatories, which are substances that increase the risk of bleeding by inhibiting the action of platelets, do not need to be discontinued prior to colonoscopy. The major concern is in relation to anticoagulants, such as heparin and warfarin. In these cases, the decision to stop is left to the doctor, who will assess the risks and the benefits.

Does the colonoscopy test hurt?

Our gut looks like one of those empty party balloons. Its interior is hollow, but the walls are "glued" to each other. In order for the colonoscope to enter and visualize the walls of the large intestine at all angles, it is necessary to cause an insufflation of the colonoscope. So while the colonoscope is being introduced it goes at the same time throwing air (actually carbon dioxide) inward, thus taking off the walls and allowing its progression.

The discomfort that colonoscopy causes is due to the air used to inflate the colon. The patient usually experiences cramps, which may be stronger or weaker depending on each case. As air is injected into the intestine, during the examination the patient often feels like eliminating flatus (dropping pum). It is not necessary to be ashamed and one should not try to prevent the exit of these gases. In fact, eliminating the air helps the doctor to have an idea of how much you tolerate the insufflation, allowing it to control so that the examination is less uncomfortable.

There are people who find colonoscopy a very uncomfortable exam, while there are others who tolerate it without problems. This is very individual, but it also depends on the skill of the doctor.

Sedation during colonoscopy

Colonoscopy can be done without sedation, with mild sedation or with deeper sedation. When deeper sedation is desired, usually an anesthesiologist is called to follow the examination.

The degree of sedation is decided according to the level of anxiety of the patient, their ability to cooperate during the examination and the conditions of their clinical condition. Obese patients with heart or lung disease, for example, tolerate poorly aggressive sedation. The ideal is to always perform the examination with the minimum of sedation necessary for the patient to feel well and allow the colonoscopy to be performed properly. In general, patients become sleepy but remain awake.

Before the examination, ask your doctor how he plans to perform your sedation.

How is the colonoscopy done?

At the time of the examination you will be placed aside and your vital signs monitored. A nurse will pick up a vein from you for administration of serum and medications. When you are relaxed and adequately sedated, the examination will begin.

The doctor will introduce the colonoscope through your anus, progressing slowly through the rectum and then colon, as you inject carbon dioxide to inflate the intestinal loops. During the examination the doctor may ask you to make small movements with the body in order to facilitate the passage of the colonoscope.

If the doctor identifies polyps during the procedure, they can be removed by the colonoscope. Likewise, suspected lesions can be biopsied for best evaluation by a pathologist looking for signs of cancer. The result of the evaluation of the withdrawn material usually takes a few days to be released.

The test takes between 20 and 60 minutes. If the colon cleansing is not satisfactory, the doctor usually chooses to stop the examination, rescheduling it to another date.

The sedative takes time to disappear completely. Patients may have to remain in the clinic for 1 to 2 hours after the end of the colonoscopy. Full recovery from sedation is only planned for the following day. Therefore, the patient should always be accompanied for the examination, because someone will have to help him return home. The patient should no longer work, drive vehicles, or operate heavy machinery on this day.

After arriving home the patient can have a snack or dinner, if desired. If the doctor has removed one or more polyps, it may indicate a special diet for the next few days. In cases where polyps or biopsies have been removed from suspected lesions, a small amount of blood in the first stool after the examination is normal. However, large amounts of blood and/or persistent stool bleeding are uncommon and should be reported to the doctor.

Cramps and flatus elimination may occur for an hour or two after the procedure. If you are still full of gas when you get home, walking helps eliminate them.

Risks of colonoscopy

Colonoscopy is a very safe exam. However, like any medical procedure, there is always a risk of problems. The complication rate is 0.2% and the risk of death is 0.007%. Complications are most common when you need to remove one or more polyps. Still, the risk is very low.

Bleeding can occur from biopsies or removal of polyps, but is usually minimal and can be easily controlled. Another possible but rare complication is the perforation of the colon.

It is possible to have side effects of the medicines used for sedation.

Transmission of diseases by the colonoscope is very rare and could theoretically only occur if it is not adequately sterilized after each examination. There are no reports of cases of HIV transmission through colonoscopy.

You should contact your doctor immediately if you experience any of the following symptoms after the test:
  • Severe abdominal pain (not just gas cramps)
  • Great distension of the abdomen
  • Vomiting
  • Fever
  • Persistent or large volume bleeding in the stool

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