Skip to content
My WebMD Sign In, Sign Up

Colorectal Cancer Health Center

Font Size

Colonoscopy

What Happens During a Colonoscopy?

The colonoscopy is performed by a doctor experienced in the procedure and lasts approximately 30-60 minutes. Medications will be given into your vein to make you feel relaxed and drowsy. You will be asked to lie on your left side on the examining table. During a colonoscopy, the doctor uses a colonoscope, a long, flexible, tubular instrument about 1/2-inch in diameter that transmits an image of the lining of the colon so the doctor can examine it for any abnormalities. The colonoscope is inserted through the rectum and advanced to the other end of the large intestine.

The scope bends, so the doctor can move it around the curves of your colon. You may be asked to change position occasionally to help the doctor move the scope. The scope also blows air into your colon, which expands the colon and helps the doctor see more clearly.

You may feel mild cramping during the procedure. You can reduce the cramping by taking several slow, deep breaths during the procedure. When the doctor has finished, the colonoscope is slowly withdrawn while the lining of your bowel is carefully examined.

During the colonoscopy, if the doctor sees something that may be abnormal, small amounts of tissue can be removed for analysis (called a biopsy), and abnormal growths, or polyps, can be identified and removed. In many cases, colonoscopy allows accurate diagnosis and treatment without the need for a major operation.

What Do I Need to Do Before a Colonoscopy?

Before a colonoscopy, let your doctor know about any special medical conditions you have, including the following:

  • Pregnancy
  • Lung conditions
  • Heart conditions
  • Allergies to any medications
  • If you have diabetes or take medications that may affect blood clotting; adjustments to these medications may be required before the colonoscopy.

Never stop taking any medication without first consulting your doctor.

You may need to take antibiotics before the colonoscopy if you:

  • Have an artificial heart valve
  • Have ever been told you need to take antibiotics before a dental or surgical procedure

 

How Do I Prepare for a Colonoscopy?

There may be some diet or fluid restrictions before you have a colonoscopy, but this will vary according to your doctor's instructions. You may be asked to limit or eliminate solid foods for a few days before the test. You may also be asked to take laxatives by mouth. Along with the dietary changes, your bowel must be further cleansed in order for colonoscopy to be successful. You will receive 2 enemas before the procedure because the rectum and lower intestine must be empty so that the intestinal walls can be seen. You will need to try to hold the enema solution for at least 5 minutes before releasing it.

Make sure you arrange for a driver to bring you home after the colonoscopy. Because you receive sedating medication during the procedure, it is unsafe for you to drive or operate machinery for 8 hours after the procedure.

Today on WebMD

Colorectal cancer cells
The right diagnosis is the most important factor.
man with a doctor
Our health check will steer you in the right direction.
 
sauteed cherry tomatoes
Fight cancer one plate at a time.
bladder cancer x-ray
Do you know the warning signs?
 
bread
ARTICLE
Colon vs Rectal Cancer
VIDEO
 
New Colorectal Treatments
VIDEO
can lack of sleep affect your immune system
FEATURE
 
Cancer Facts Quiz
QUIZ
Virtual Colonoscopy
VIDEO
 
Picture of the Colon
ANATOMY
Vitamin D
SLIDESHOW
 

WebMD Special Sections