colonoscopy procedure

Colonoscopy is one of the most important examinations that are performed to detect diseases and abnormal changes that affect the colon. It is used for diagnostic or therapeutic reasons, depending on the case.

An overview of the colon

The colon forms the largest part of the large intestine, with a length of about 150 cm. The colon absorbs water and salts from the waste before excreting it, as the colon forms a passage for the stool to pass into the rectum, and then out of the body through the anus.

The colon is divided anatomically according to its location into four sections:

  • ascending colon
  • transverse colon
  • descending colon
  • sigmoid colon
Anatomical position of the colon and rectum
Image showing normal positioning of the colon and rectum

What is a colonoscopy?

In colonoscopy, the doctor inserts a long, flexible tube with a camera at the bottom through the anus, into the rectum, and into the distal parts of the colon.

The endoscope is connected to a screen where what the camera captures is displayed on the screen, enabling the examiner to see the colon and examine it and identify pathological changes, if present.

During the endoscopy, the patient is anesthetized so that no pain is felt. Endoscopy can be used for therapeutic reasons, meaning that if a mass is suspected within the colon, a biopsy can be taken through endoscopy for examination, and healthy masses and polyps can also be removed.

How to perform a colonoscopy
This picture shows the colonoscopy

Why is colonoscopy used?

The doctor advises the patient to undergo a colonoscopy for one of the following reasons:

  • The presence of gastrointestinal symptoms such as bleeding, abdominal pain, and the presence of chronic constipation or diarrhea.
  • revealing of colorectal cancer The presence of polyps in the colon.
  • Suspicion of inflammatory bowel diseases such as ulcerative colitis and Crohn's disease.
  • Colonoscopy is done regularly in patients who have an increased risk of colorectal cancer, such as a family history of the disease or advanced age.

Preparation before a colonoscopy

There are some instructions that the patient must follow before performing the endoscopy in order to clean the colon from the stool that obstructs the entry of the endoscope so that the examining doctor obtains a clear view of the colon.

Diet before the endoscopy

Some foods such as corn, nuts and red meat should be avoided about three days before the endoscopy. It is preferable for the patient to adhere to a low-fiber diet several days before the endoscopy.

You should refrain from eating solid foods and alcohol a day before the procedure, and four hours before the endoscopy, you should not eat food at all.

The most important thing is to follow your doctor's instructions regarding diet.

drink laxatives

The doctor often advises the patient to take laxatives before the endoscopy. The laxatives are either in the form of pills or in the form of a drink that the patient drinks. It is recommended to take laxatives the night before the endoscopy or the morning of the endoscopy.

Modify some medications

The doctor should be consulted about the medications taken. The doctor may ask the patient to adjust some medications before the endoscopy or reduce the dose taken. For example, if the patient is taking blood-thinning drugs such as warfarin, it can be stopped temporarily before the endoscopy to reduce the risk of bleeding.

The patient is advised to take a driver or a family member with him to the hospital or clinic where the endoscopy is performed. The reason behind this is that the patient may be sedated during the endoscopy, so another person will need to drive the car instead of him on the way back.

During a colonoscopy

A colonoscopy is performed either in a hospital or outpatient setting by a doctor experienced in the procedure.

During the procedure, the patient is dressed in a special gown and is lying on his left side with his knees raised towards his chest (fetal position). The patient is anesthetized either with regional anesthesia, i.e. the patient remains awake without feeling any pain, or general anesthesia is performed in some cases.

The examining doctor inserts the colonoscope through the anus. The endoscope is equipped with a camera and is long enough to reach all parts of the colon. The endoscope contains a small lamp and a channel that enables the doctor to release air through which the air expands the colon and gives the doctor a clearer view.


The doctor looks for any abnormal changes in the colon and may take a biopsy of the colon if he suspects the presence of a cancerous mass, and if a polyp is found, the doctor will remove it.

After the examination is completed, the doctor gently pulls the endoscope out. The patient may feel cramps during the withdrawal. The cramps can be relieved by resting and taking a deep breath.

In fact, colonoscopy takes about half an hour or less in normal cases, but if a polyp or mass is found, it may take longer.

After colonoscopy

After the endoscopy, the patient remains in the hospital to recover and to ensure that there are no complications related to the endoscopy. The recovery period depends on the type of anesthesia the patient received during the endoscopy.

You should avoid driving a car or doing strenuous activities for at least 24 hours after the procedure and avoid alcohol and smoking for at least a day after the endoscopy.

The patient may feel cramps or abdominal cramps temporarily, which will disappear quickly. The patient may not defecate for several days after the endoscopy due to the complete emptying of the colon. If the doctor removed a polyp during the endoscopy, the patient may notice slight rectal bleeding for a day or two after the colonoscopy.

The examiner determines the need to stop taking diluents or adjust medications after the endoscopy.

Colonoscopy results

After the endoscopy, the doctor explains to the patient what happened during the endoscopy in the event that a polyp was removed or an abnormal tissue was suspected from which a biopsy was taken.
Endoscopy results are either:

Endoscopy results are negative

Meaning that no abnormal changes were detected at the level of the colon and rectum, meaning that the examination was normal and there is no need for concern or fear. The doctor advises the patient to repeat the endoscopy during:

  • 10 years in the absence of a risk factor for colon cancer.
  • 5 years if there are previous polyps that have been removed.
  • annually in the event that there is a high risk factor for cancer, such as familial polyposis, which greatly increases the risk of colon cancer.

Endoscopy results are positive

The results are considered positive if polyps are detected during the endoscopy or if abnormal tissue is detected in the colon.
In most cases, the polyps are not malignant, but there is a risk that the polyp will turn into a cancerous lesion, so the doctor will remove the polyp as soon as it is discovered.

The doctor may ask the patient to repeat the endoscopy soon if:

  • Presence of one or more polybins
  • Large polyp larger than 1 cm
  • The polyp has a shape that is close to a cancerous lesion

In the event that the doctor is unable to remove the polyps through laparoscopy, the patient may be referred to a surgical procedure to remove them.

No results

Meaning that the doctor was not able to examine the colon clearly because of the presence of a faecal mass that obstructs the entry of the endoscope. This occurs due to the poor preparation of the patient before the endoscopy.

In this case, the doctor asks the patient to repeat the colonoscopy within a short period with good preparation.

Colonoscopy risks

In general, colonoscopy is a safe procedure, as the risk of complications is fairly low. Of the complications related to endoscopy that can occur:

  • Bleeding following a biopsy or laparoscopic polypectomy
  • A tear in the wall of the colon or rectum
  • Anesthesia related problems
  • Sepsis if the endoscope used is contaminated
  • Some complications occur before the endoscopy, such as excessive use of laxatives, which causes irritation to the skin around the anus due to continuous defecation.

Colonoscopy Instructions

It is recommended to start regular colonoscopy at the age of 45, once every ten years. Colonoscopy is the best way to reduce the risk of colorectal cancer and to detect it early if it occurs.

In some cases, periodic colonoscopy must be started at an earlier age, i.e. before the age of 45, in one of the following cases:

  • Having a first-degree relative with colorectal cancer
  • Inflammatory colon diseases such as ulcerative colitis or Crohn's disease
  • Having genetic diseases that increase the risk of cancer, such as familial polyposis and Lynch syndrome

Tests alternative to colonoscopy for cancer screening

There are alternative tests to colonoscopy in order to prevent cancer, such as:

sigmoid colonoscopy

In fact, this test is somewhat similar to a colonoscopy, but with a sigmoid colonoscopy, the scope is shorter and is used to view only the rectum and sigmoid colon. That is, the sigmoid colonoscope cannot examine all sections of the colon.

Virtual colonoscopy

Also called computed tomography of the colon, it is a less invasive procedure than colonoscopy. This technique relies on shining several sources of x-rays that are controlled by a computer. The computer combines the images with each other and gives a three-dimensional image of the rectum and colon.

Swallow a capsule containing a camera

In fact, this method is used to see the small intestine rather than the large intestine, where a small pill containing a camera is swallowed and this capsule travels through the digestive system from the mouth to the colon.

This method is often used for imaging the small intestine, because it is difficult to see the colon due to aliasing and the large size of the colon, in addition to the difficulty of cleaning the colon to obtain a clear view.

fecal transplant

A stool sample is taken and examined in the laboratory. The occult blood in the stool is investigated, in addition to DNA testing and the necessary immunochemical tests. More information about stool culture from Here.

The relationship between colorectal cancer and colonoscopy

Colorectal cancer is one of the most common cancers that affect the elderly, as it is the most common cancer of the digestive system.

Colonoscopy is the primary screening test for colorectal cancer studies are one of the following:

  • Cancer mortality decreased due to periodic colonoscopy
  • Endoscopic excision of polyps reduced the risk of polyps turning into cancer

Frequently Asked Questions

Colonoscopy is often not painful because the patient is sedated during the colonoscopy with either local or general anesthesia.

Before the colonoscopy, you must adhere to a diet prescribed by the doctor to empty the colon of waste, in addition to the possibility of taking laxatives the day before the endoscopy to completely empty the colon.

In normal cases, colonoscopy should be done periodically once every ten years at the age of 45 in order to exclude colorectal cancer and detect it early, and colonoscopy is done in pathological cases when there are symptoms of colon problems such as chronic constipation or suspicion of infections at the colon level or to remove polyps intact.

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you can talk to us here.