Colonoscopy: All You Need To Know

Medically Reviewed by Dr. K. on 17.5.2021.


A colonoscopy is a procedure in which the doctor examines the inside of the large intestine to check at the source of symptoms such as abdominal pain, rectal bleeding, or changes in bowel habits. During a colonoscopy, your doctor examines your large intestine, especially the colon, for anomalies or disease. A colonoscope is a thin, flexible tube with a light and camera connected to it.

The colon contributes to the formation of the gastrointestinal tract’s lower part. It processes food, absorbs nutrients, and eliminates waste.

The rectum connects the intestine to the anus. The anus is the bodily cavity from which faeces are expelled.

Colonoscopies are often used to screen for colorectal cancer, and they can begin at the age of 45. Your doctor can take tissue samples for biopsy or remove suspicious tissue such as polyps during a colonoscopy.

Don’t be alarmed if the doctor suggests a colonoscopy. You might expect it to be a painful operation, but it won’t be. You might not even recall anything because you won’t be conscious. (Most people believe the procedure’s preparation to be the most difficult part.)

What Do I Do Before Exam?

Let your doctor know of any medical conditions you have before doing a colonoscopy, such as:

  • Pregnancy
  • Kidney disease
  • Lung conditions
  • Heart conditions
  • Allergies to medications

Tell the doctor whether you have diabetes or are taking any medications that can affect blood clotting. Before the surgery, they may need to adjust to these medications.


A clean colon is needed for a successful colonoscopy. That means you must restrict your diet for at least 24 hours prior to the operation. A food guide can be provided to you to give you more information of what foods you can or cannot consume. Solid foods are normally off-limits, but clear liquids like:

  • Coffee
  • Broth
  • Water
  • Sports drinks

After that, you should empty your bowels. Your doctor would most likely ask you to take care of it in one of two ways:

  • Drink a laxative recommended by the doctor, most usually polyethylene glycol, to push you to go.
  • Enemas can be used in addition to the laxative.

They may recommend you to do it the night before or on the morning of your colonoscopy. Make sure you follow their instructions to the letter.

Make arrangements for someone to drive you home after the colonoscopy. You will be sedated, which means you will not be conscious throughout the process. After that, you won’t be able to move or handle machines for at least 8 hours.

Colonoscopy Procedure

You’ll lay on your left side on an exam table for your colonoscopy. You’ll be given sedatives with an IV in your arm. This can relax you and make you unconscious so you are unaware of the procedure.

During the procedure, the doctor inserts a colonoscope, which is a tube-like device, into the rectum. It’s about a half-inch long and a half-inch wide. It has a light and a video camera on the tip, allowing the doctor to examine the lining of the colon to determine whether or not there is an issue.

A tube attached to the colonoscope allows the doctor to inflate the colon by pumping air into it. This will enable them to see the colon and its lining more clearly.

Your doctor will use a small snare in the colonoscope to collect tiny samples of the colon for testing during the procedure, which is known as a biopsy. They will also use it to remove polyps, which are abnormal growths.

What Happens After the Exam?

It could take between 20 and 30 minutes to complete the operation. To recover from the sedative, you’ll spend 30 minutes to an hour in a recovery room.

You may experience cramping or pass gas, which are both normal. Once you leave the doctor’s office, you may resume your normal eating schedule.

Before you go, double-check if you understand the instructions. When your doctor performed a biopsy or extracted some polyps, you might need to avoid medications such as blood thinners for a day or two.

Risks and Complications

Since a colonoscopy is a common procedure, there are usually few long-term effects. The advantages of identifying symptoms and initiating treatment far outweigh the risks of complications from a colonoscopy in the overwhelming majority of cases.

However, there are a few rare complications:

  • bleeding from a biopsy site if a biopsy was done
  • a negative reaction to the sedative being used
  • a tear in the rectal wall or colon

Digital colonoscopy is a technique that utilises CT scans or MRIs to take photos of the colon. You can avoid a few of the complications associated with traditional colonoscopy if you choose it instead.

However, it has its own set of drawbacks. It might not be able to identify very tiny polyps, for example. It’s even less likely to be covered by health insurance because it’s a newer technology.

If you experience any of the following symptoms, call the doctor right away:

  • Bleeding that is more than a little or that persists a long time
  • Intense abdominal pain
  • Fever or chills


Referenced on  14/4/2021 

  1. American Cancer Society.
  2. Mayo Clinic, “Colonoscopy.”
  3. Harvard Health Publications, “Preparing for a colonoscopy.”
  4. The American Cancer Society medical and editorial content team. (2020). American Cancer Society guideline for colorectal cancer screening.
  5. Buskermollen M, et al. (2019). Colorectal cancer screening with faecal immunochemical testing, sigmoidoscopy or colonoscopy: A microsimulation modelling study. DOI:
  6. Colonoscopy. (2017).
  7. Colonoscopy. (2017).
  8. Mayo Clinic Staff. (2020). Colonoscopy.
  9. Qaseem A, et al. (2019). Screening for colorectal cancer in asymptomatic average-risk adults: A guidance statement from the American College of Physicians. DOI:
  10. Understanding colonoscopy. (n.d.).
  11. Virtual colonoscopy. (n.d.).

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