What to Expect During a Colonoscopy

A colonoscopy lets the physician look inside your entire large intestine, from the lowest part, the rectum, all the way up through the colon to the lower end of the small intestine. The procedure is used to look for signs of problems in the colon and rectum, including cancer.


The goal of the preparation is to clear your bowel of stool (fecal matter). There are a few ways to clean the bowel. You will be given detailed instructions by your doctor as to which method is best for you. These instructions include how you need to change your diet and what medications will be necessary to insure that your bowel is clean at the time of your colonoscopy. Follow these CLEAR LIQUID DIET INSTRUCTIONS.

The Day of Your Colonoscopy

  • Your doctor may ask you to perform a Fleet enema 30 to 40 minutes before leaving your home. Follow the directions on the package.
  • If your doctor has told you take any medications, use only a small sip of water.
  • Please leave your jewelry and valuables at home.
  • You must bring a driver the day of your procedure. You will not be allowed to drive yourself home. Your procedure will be canceled if you do not have a responsible adult to drive you home.

How is the Procedure Done?

For the colonoscopy, you will lie on your left side on the examining table. You will be given pain medication and a mild sedative to keep you comfortable and to help you relax during the exam. Your doctor will insert a long, thin, flexible, lighted tube, called a colonoscope, into your rectum and slowly guide it into your colon. The scope bends, so the doctor can move it around the curves of your colon and transmits images of the inside of the colon for your doctor to see. You may be asked to change position occasionally. The scope also blows air into your colon, which inflates the colon and improves visibility.

How long will it take?

A colonoscopy takes 30 to 60 minutes. The sedative and pain medicine should keep you from feeling much discomfort during the exam. You will need to remain at the hospital for 2 to 3 hours, until your sedative wears off.

What if they find something unusual?

If anything abnormal is seen in your colon, such as a polyp or inflamed tissue, your doctor can remove all or part of it using instruments passed through the scope. The tissue (biopsy) is then
sent to a lab for testing.


Bleeding and puncture of the colon are possible, but uncommon. If there is bleeding in the colon, your doctor can control the bleeding by using a laser, a heat or electrical probe, or by injecting
medication. These procedures do not usually cause any pain. Some people might have a reaction to the sedatives or complication due to pre-existing heart or lung disease.

At Home

  • If you feel severe abdominal pain or have a fever, bloody bowel movements, dizziness or weakness, call us immediately.
    • Upper GI (716) 845-4774
    • Lower GI (716) 845-4660
    • After clinic hours and on weekends and holidays, please call (716) 845-2300 and ask for the GI doctor on call.
    • If you live in the Buffalo area and need to go to an emergency room, please go to Buffalo General Hospital Emergency Department. Roswell Park has a collaborative relationship with Buffalo General to help you in the case of an emergency. The doctors and nurses at Buffalo General Hospital have access to your Roswell Park medical records and will work with Roswell Park to coordinate your medical care. Remember to bring your green Roswell Park ID card to help them access your records.

    • If you live outside of the Buffalo area, please go directly to your nearest hospital emergency department.

Instructions for CLEAR LIQUID DIET in preparation for your colonoscopy

Drink only a clear liquid diet the day before your surgery. Liquids that you can see through at room temperature (about 78-72°) are considered clear liquids.


  • Soft drinks (orange, ginger ale, cola, lemon/lime, etc. – not red or purple)
  • Gatorade or Kool Aid (not red or purple) • Strained fruit juice without pulp (apple, orange, lemonade) • Water or flavored waters • Tea or coffee (may add sugar, but no milk or creamers)


  • Chicken broth or bouillon
  • Beef broth or bouillon
  • No added meats, noodles or vegetables


  • Hard candy
  • Jell-O (not red or purple – and no fruit toppings or whipped cream)
  • Popsicles or lemon ice (not red or purple – and no sherbets or fruit bars)