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Please Note: This page is related to procedures at Credit Valley Hospital site of Trillium Health Partners. Some of these procedures are also available at our Mississauga Hospital site - see Mississauga Hospital endoscopy procedures page » or see main Endoscopy page »

Understanding Colonoscopy

What is a colonoscopy?

Colonoscopy enables your doctor to examine the lining of your colon (large intestine) for abnormalities by inserting a flexible tube as thick as your finger into your anus and slowly advancing it into the rectum and colon. If your doctor has recommended a colonoscopy, this brochure will give you a basic understanding of the procedure - how it's performed, how it can help, and what side effects you might experience. If you have additional questions, please ask your doctor.

What preparation is required?

Please choose one of the bowel preparations below as instructed by your physician.



 Credit Valley Hospital Procedures - Prep

Colonoscopy BiPegLyte Preparation -Morning.pdfColonoscopy BiPegLyte Preparation -Morning
Colonoscopy BiPegLyte Preparationpm Afternoon.pdfColonoscopy BiPegLyte Preparationpm Afternoon
Colonoscopy Moviprep Preparationam Morning.pdfColonoscopy Moviprep Preparationam Morning
Colonoscopy Moviprep Preparationpm Afternoon.pdfColonoscopy Moviprep Preparationpm Afternoon
Colonoscopy PEG Preparation AM.pdfColonoscopy PEG Preparation AM
Colonoscopy PEG Preparation PM.pdfColonoscopy PEG Preparation PM
Colonoscopy Pico Salax Preparationam Morning.pdfColonoscopy Pico Salax Preparationam Morning
Colonoscopy Pico Salax Preparationpm Afternoon.pdfColonoscopy Pico Salax Preparationpm Afternoon


Can I take my current medications?

Most medications can be continued as usual, but some medications can interfere with the preparation or the examination. Inform your doctor about medications you're taking, particularly aspirin products, arthritis medications, anticoagulants (blood thinners), insulin or iron products. Also, be sure to mention allergies you have to medications.

What happens during colonoscopy?

Colonoscopy is well-tolerated and rarely causes much discomfort. You might feel pressure, bloating or cramping during the procedure. Your doctor will likely give you a sedative to help you relax and better tolerate any discomfort.

You will lie on your side or back while your doctor slowly advances a colonoscope through your large intestine to examine the lining. Your doctor will examine the lining again as he or she slowly withdraws the colonoscope.

The procedure itself usually takes 10 to 15 minutes, although you should plan on two to three hours for waiting, preparation and recovery.

What if the colonoscopy shows something abnormal?

If your doctor thinks an area needs further evaluation, he or she might pass an instrument through the colonoscope to obtain a biopsy (a sample of the colon lining) to be analyzed. Biopsies are frequently done during colonoscopy and used to diagnose various conditions. If colonoscopy is being performed to identify sites of bleeding, your doctor might control the bleeding through the colonoscope by injecting medications or by coagulation (sealing off bleeding vessels with heat treatment). Your doctor might also find polyps during colonoscopy, and he or she will most likely remove them during the examination. Taking biopsies and removing polyp(s) does not cause any discomfort.

What are polyps and why are they removed?

Polyps are abnormal growths in the colon lining that are usually benign (noncancerous). They vary in size from a tiny dot to several centimeters. After the polyp(s) is removed, your doctor will have it analyzed and you will be informed of the result once available.  Removal of polyp(s) is an important means of preventing colon cancer.

How are polyps removed?

There are various ways to remove polyp (s).  Your doctor sometimes use cautery (electrical current); may use  wire loops called snares or  biopsy instruments. 

What happens after a colonoscopy?

Your physician will explain the results of the examination to you, although you'll probably have to wait for the results of any biopsies performed.

If you have been given sedatives during the procedure, someone must drive you home and stay with you. Even if you feel alert after the procedure, your judgment and reflexes could be impaired for the rest of the day. You might have some cramping or bloating because of the air introduced into the colon during the examination. This should disappear quickly when you pass gas.

You should be able to eat after the examination, but your doctor might restrict your diet and activities, especially after polypectomy.

What are the possible complications of colonoscopy?

Colonoscopy and polypectomy are generally safe when performed by doctors who have been specially trained and are experienced in these procedures.

One possible complication is a perforation, or tear, through the bowel wall that could require surgery. Bleeding might occur at the site of biopsy or polypectomy, but it's usually minor. Bleeding can stop on its own or be controlled through the colonoscope; it rarely requires follow-up treatment. Some patients might have a reaction to the sedatives or complications from heart or lung disease.

Although complications after colonoscopy are uncommon, it is important to recognize early signs of possible complications. If you notice severe abdominal pain, fever and chills, or rectal bleeding of more than one-half cup contact your doctor or go to the nearest hospital . Note that bleeding can occur up to10 days after the procedure.