Colonoscopy and preparation of the colon

Colonoscopy is an examination that allows the doctor to examine the inner walls of the colon (rectum and colon) after appropriate preparation.
The doctor uses a thin and flexible tube called a colonoscope to look at the colon.
This examination is carried out by means of a long, thin and flexible video camera, which is included in the colonoscope.

The doctor inserts the colonoscope into the intestine via the anus.


What are the colon and rectum?

The colon and rectum are the two main parts of the colon. The colon is only a part of the colon, most of the colon is formed by the appendix (cecum), ascending colon (colon ascendens), transverse colon (colon transversum), descending colon (colon descendens), sigmoid colon and rectum. The large intestine is technically referred to as Intestinum crassum.

Why perform a colonoscopy?

Colonoscopy can be done for a variety of reasons. As a rule, it is carried out to determine the causes of:

  • blood in the stool,
  • Stomach ache
  • chronic diarrhea,
  • changes in bowel habits (bowel movements), for example, the appearance of chronic constipation or diarrhea,
  • unexplained weight loss,
  • an abnormality in the X-ray of the colon or in the CT.

The doctor advises regular colonoscopy, because the risks of polyps or colon tumors are great in:

  • people who have already had polyps or cancer in the colon;
  • people with a familial, non-intestinal tumor disease;
  • People who have colic problems that could be related to cancer of the colon (for example, ulcerative colitis).

How often a colonoscopy should be performed depends on the underlying risk and abnormality found during the previous colonoscopy.
Healthy people with a normal risk of colon cancer are advised to undergo a colonoscopy from the age of 50 and to repeat it every 10 years in order to be able to have colon polyps in the colon removed before cancerous degeneration.

Preparation for colonoscopy

The examining physician must have a clear view of the intestinal mucosa.
The hospital’s eating recommendations should be followed carefully and consist of a very light, low-residue diet for 1 or 2 days before the examination.
The patient is allowed to drink clear liquids in the morning only if the colonoscopy is performed in the afternoon.
For example, it is allowed to suck candy or drink tap water or highly diluted clear drinks.
In addition, the solution for colon cleansing must be drunk at the times indicated.

To empty the colon, the doctor may ask to change the diet:

Follow a special diet the day before the examination. As a rule, no solid foods are eaten before the day of the examination. drinks are limited to clear liquids, plain water, tea and coffee without milk or cream, broth; Avoid carbonated drinks.

In the three days prior to the examination, the eating recommendations listed in the following table should be followed:


to avoid
Permitted foods



Whole grains

Fruit juice with pulp



Alcoholic beverages


Lean meat 


Skimmed cheese




Skimmed milk

Rice and bread made from white flour


Avoid red drinks, which may cause confusion with blood during colonoscopy.
The night before the examination, you are not allowed to eat or drink anything after midnight.

Take laxatives. The doctor may recommend a laxative in the form of tablets or in liquid form.
It is likely that you will need to take a laxative the evening before the colonoscopy, or the doctor may ask you to take one the night before and the morning of the procedure.

Use an enema kit. In some cases, it may be necessary to use an over-the-counter enema kit both the night before the examination and a few hours before the examination.

Adjust medication. Tell the doctor about the medications you have been taking at least a week before the examination, especially if you have diabetes, high pressure or heart problems, if you are taking medications or supplements that contain iron, or if you are taking aspirin or other blood-thinning medications such as warfarin (Coumadin) or clopidogrel (Plavix).
Temporary dose adjustment or discontinuation of medication may be required.

Laxatives for colonoscopy

  • If the colonoscopy takes place in the morning, it is necessary to take 12 liters of water with 3 sachets of laxative dissolved in it about 3 hours before; In the morning before the examination (around 6 o’clock) you have to dissolve another bag of laxatives in a liter of water and drink.
  • If the colonoscopy takes place in the afternoon, 2 liters of water with 2 sachets of laxative are taken in the evening and the same amount again in the morning before the examination (around 10 am) (2 sachets in 2 l of water).

Phospho-soda ash
Phospho-soda is a powder that is available as an over-the-counter medication alone or as part of a kit containing laxatives and an enema or suppository.
The doctor responsible for the colonoscopy will give instructions on what type of kit to get.

Make a drink with three ounces of liquid phospho-soda mixed with water or, if the doctor allows, with another clear liquid such as ginger ale.
After drinking the phospho-soda mixture, the patient needs to drink at least three more glasses of another clear liquid.
Part of the kit or the rest of the kit (laxative, enema or suppository) is used as directed by the doctor.

This preparation usually causes the stimulus for defecation within 30 minutes to 6 hours after ingestion.
Phospho soda is also available in different tastes that make it more enjoyable.

Most doctors ask patients to notify them if the preparation does not go as intended (for example, if there is no bowel movement or if the excretion does not become clear).

Sodium phosphate
Sodium phosphate tablets are prescribed by the doctor who performs the colonoscopy. There are two different brands, depending on the doctor’s prescription: Fleet Phospho-Soda and Phospho-Lax.

The preparation begins with its action about an hour after taking the first dose of the tablet.
A diet with liquid food is ordered about 12 hours before the examination. Possible side effects include bloating, nausea, vomiting and abdominal pain.

What happens during the examination?

Colonoscopy is performed on an outpatient basis and lasts 20-40 minutes. To induce a relaxed and sleepy state during the examination, a sedative is injected directly into the vein.
The patient is asked to lie on his side during the examination.
The colonoscope is provided with a lubricant and carefully inserted into the intestine via the anus. The doctor carefully pumps air into the intestine to improve visibility of the intestinal mucosa. This can lead to flatulence in the patient. But it is important to keep the air until the end, until the doctor has taken all the pictures and made necessary sampling.

Today, many doctors prefer to look at the images from the colonoscopy on the screen next to the patient and do not look directly through the colonoscope.
Patients can, if they wish, follow the process on the screen.
Sometimes the doctor needs to take small tissue samples.
This procedure is completely painless.
The tissue is sent to a laboratory for assessment, the results are usually available after a few days.

If a piece of tissue, such as a large polyp, is removed, it may be necessary to stay in the hospital for a few hours for observation due to possible postoperative bleeding.
The patient may rest after the examination until the effect of the sedation has passed. After that, he can go home.
Patients are unable to drive home by car due to sedation and must be monitored by an adult for over 24 hours after the examination.

Recovery time after colonoscopy

The colonoscopy takes about 30-60 minutes. In the first hour after the examination, cramps or flatulence may occur. The sedative needs time to be completely broken down again.
Patients may need to remain in the hospital for 1 or 2 hours. A full recovery is expected in the course of the next day.
The hospital’s instructions should be carefully read and followed.
Patients who develop any of the following rare side effects should contact the doctor immediately:

  • Severe abdominal pain
  • Fever
  • Significant blood loss from the anus
  • Vertigo
  • Weakness

At what age should a routine colonoscopy be performed?

A regular colonoscopy for cancer screening should begin for most people from the age of 50.
The doctor may advise earlier if there is a family predisposition to colorectal cancer, a personal history of inflammatory bowel disease or another risk factor.

Does a colonoscopy hurt?

According to some people, a colonoscopy is cumbersome and painful, especially because the doctor pumps a lot of air into the intestines, creating a feeling like colic.
Others, on the other hand, hardly feel any pain. So the statement is very subjective.
As a rule, the patient sleeps after sedation, but in some cases he remains awake.

What should be considered after a colonoscopy?

Most people can return home after half an hour of rest. It may be necessary to stay a little longer for observation after any polyps have been removed.
The sedative gives the feeling of well-being and relaxation.
Nevertheless, you must not drive a car, operate machines, drink alcohol, make important decisions or sign documents until the drug has been completely eliminated from the body after 24 hours.
It is necessary that the patient is accompanied home by someone and this remains with him for the first 24 hours until the effect has completely passed.
Most people can resume their normal activities after 24 hours.

The examining physician writes the result (report) and sends it to the doctor who requested the colonoscopy. The result of the biopsy takes a few days and may delay the sending of the report.
The doctor can also tell the patient directly orally what he saw during the colonoscopy.
However, after taking the sedative, it is possible that the patient does not remember what the doctor tells him.
It therefore makes sense to take a relative or close friend with you, who can still remember the words of the examining doctor.

Long-term perspectives

A swelling, pain and flatulence can pass in a few days.
These symptoms are caused by the air pumped into the intestines during the examination. The doctor must be consulted again to discuss the result from the colonoscopy. Treatment depends on the diagnosis.

Are there any side effects or complications after a colonoscopy?

Complications arise if there are problems during or after the examination. The main problems associated with a colonoscopy are listed below:

  • The doctor may not be able to see into all sections of the intestine. This may be the case if the bowel was not completely empty or if it is impossible to insert the colonoscope into a curve. If this happens, a repetition of the colonoscopy or another type of examination may be necessary.
  • There may be a reaction with breathing symptoms or heart symptoms to the sedative. The patient must be monitored throughout the procedure and treated immediately if symptoms develop.
  • The colonoscope and other instruments used in colonoscopy can injure or tear the intestines. If this happens, an operation may be required to recover.
  • Heavy bleeding may occur if the doctor takes a biopsy or removes a polyp.
  • Rarely, the colonoscope can cause damage to the colon. This can lead to bleeding, infection and perforation of the colon.

What are the alternatives to colonoscopy?

Colonoscopy is the best examination to look at the inside of the intestine. Nevertheless, it is not suitable for everyone. If colonoscopy cannot be performed, the doctor recommends other examinations. The main alternatives are:

Barium enema. A liquid containing barium (a substance presented in the X-ray) is introduced into the intestine via the anus. Radiography of the abdomen (abdomen) shows the inside of the intestine.

Virtual colonoscopy. This examination consists of a CT scan of the abdomen after a gas is pumped into the colon to dilate it. CT uses X-rays to display three-dimensional images of the colon and rectum.

Flexible sigmoidoscopy. This is a procedure similar to colonoscopy, but uses a shorter instrument to look at the rectum and lower intestinal section.

Results of colonoscopy

Depending on the size and number of polyps, more precise examination planning for the future may be necessary. If the doctor detects one or two polyps measuring less than 1 cm in diameter, a new colonoscopy after 5 or 10 years may be sufficient, depending on other risk factors for colon cancer.

For larger polyps or if the cells have characteristic changes, the doctor may recommend another colonoscopy in 3-5 years if other risk factors are present.
If one or more cancer-suspected polyps were removed during colonoscopy, the doctor may recommend a control colonoscopy in less than three months, six months, or a year.
If a polyp or other conspicuous tissue could not be removed during the colonoscopy, the doctor may suggest a check in the practice.

If the doctor is concerned about the quality of vision during the colonoscopy, he or she may recommend a new colonoscopy at an early time. If the doctor cannot see the entire inside of the intestine, he may prescribe a barium enema or virtual colonoscopy to examine the rest of the intestine.

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