Colonoscopy: Preparation Before the Test, Diet and Alternatives

What should we know about Colonoscopy?

It is a test that allows your doctor to look at the inner lining of your large intestine (rectum and colon). They use a thin, flexible tube called a colonoscope that serves to observe the colon.

A colonoscopy helps detect ulcers, colon polyps, tumors, and areas of inflammation or bleeding. During a colonoscopy, tissue samples can be collected (biopsy), and abnormal growths can be extracted.

Colonoscopy can also test cancer or precancerous growths in the colon or rectum (polyps).

The colonoscope is a thin, flexible tube oscillating between 48 cm (125 cm) and 72 cm (183 cm) long. A small video camera is attached to the colonoscope so your doctor can take pictures or videos of the large intestine (colon).

The colonoscope can look at the entire colon and the lower part of the small intestine. There is an additional test called sigmoidoscopy, which shows only the rectum and the lower part of the colon.

Process before Colonoscopy – Preparation

Before this test, you will have to cleanse your colon (a process known as colon preparation). Colon preparation takes 1 to 2 days, depending on the type your doctor recommends.


Some preparations can be taken the whole night before the test. For many people, the practice is worse than the test. Bowel preparation can be uncomfortable, and you may feel hungry during the liquid diet.

Plan to stay at home during your preparation time since you will need to use the bathroom often. Colon preparation causes loose and frequent stools and diarrhea so that your colon is emptied for testing.

If you need to take a unique solution as part of your preparation, have clear fruit juices or soft drinks to drink after the practice because the solution may have a salty or unpleasant taste.

Colonoscopy is one of many tests that can be used to detect colon cancer. Other tests include sigmoidoscopy, stool tests, and computed tomographic colonography.

The screening test you choose depends on your risk, preference, and doctor. Talk to your doctor about which test is best for you.

Colonoscopy is done to check for colorectal cancer or polyps.

This test is recommended by many experts and groups, including the American Cancer Society (SAC) and the United States Preventive Services Task Force.

These groups recommend routine tests for people 50 years of age or older who have an average risk of colorectal cancer.

Your doctor may recommend an earlier or more frequent test if you have a higher risk of getting this type of cancer. Therefore, it is always good to talk with your doctor about when you should get tested.

You should check:

  • The cause of blood in the stool or rectal bleeding.
  • The cause of dark or black stools.
  • The cause of chronic diarrhea.
  • The cause of iron deficiency anemia.
  • The cause of sudden and unexplained weight loss.

Check your colon after the abnormal results of a CT scan, MRI, virtual Colonoscopy, stool test, or barium enema.

The cause of unexplained long-term belly pain.

Other ways of preparing for the test

The places where you can perform a colonoscopy can be a hospital, a clinic, or a doctor’s office. Always, depending on the installation and the situation you are in.

Liquid diet

The patient will receive a combination of a liquid diet, laxatives, or enemas up to two days before the test with instructions on using them.

The doctor will determine the diet to be performed according to the patient’s current conditions.

There are several medications available for bowel cleansing, including polyethylene glycol 3350 (GoLYTELY, NuLYTELY), Magnesium Citrate (Citroma), and Senna (X-Prep).

These medications produce diarrhea, which can be uncomfortable, but the test may be limited and may have to be repeated later unless the bowel is empty of stool.

Are There Alternatives to Colonoscopy?

Other tests can help a doctor to detect diseases of the colon. Sometimes these tests can be done because each test can provide different types of information.

The preparation of these other tests remains similar. This is a special X-ray examination of the entire colon, a barium enema, which can be used instead of or in addition to the Colonoscopy.

A barium fluid is inserted into the colon using a small tube through the anus for this test. Then X-rays of the abdomen are taken with the barium inside. This fluid is seen on the x-ray and is used to delineate the irregularities of the intestinal wall.

Sigmoidoscopy: Computed tomography (CT) is similar to a colonoscopy but requires less preparation. A sigmoidoscope instrument is 2 feet long and allows visualization of the anal canal, the rectum, and the part of the colon closest to the rectum known as the sigmoid colon.

Although this test is essential, it does not allow the detection of abnormalities in other areas of the colon because the sigmoidoscope is much shorter than the colonoscope.

These scans are often used to investigate abnormalities of the abdomen, using Gastrografin, a liquid similar to barium, which allows the bowel to look better during a CT scan.

This fluid, also called oral contrast, is swallowed and then allowed to pass through the stomach, through the small intestine (the ileum), and then through the large intestine (colon) before the CT scan.

In this way, a computed tomography scan can help investigate abdominal and intestinal problems.

Other tests include balloon endoscopy, push endoscopy, and virtual Colonoscopy.

Your doctor will decide which of these tests is most appropriate for you.