What is a Colonoscopy?

What is a Colonoscopy?

A colonoscopy is a procedure in which your doctor can see inside the colon or large intestine using a camera inserted through the anus. The procedure is used to look for changes in the colon. It can be used as a screening test for colorectal cancer and can help to prevent colorectal cancer through the removal of precancerous colon polyps.

Why are colonoscopies done?

A colonoscopy is a diagnostic test that can help determine the underlying cause of gastrointestinal (GI) symptoms or diagnose colon diseases.

Your physician may recommend a colonoscopy for the following reasons:

  • Screening for colon cancer. A colonoscopy can check for colorectal polyps. If found, the polyps can be removed and examined—an essential procedure in the fight against colon cancer.
  • Investigating intestinal symptoms. A colonoscopy can help determine the underlying cause of rectal bleeding, abdominal pain, chronic diarrhea, prolonged constipation, or other symptoms.
  • Diagnosing intestinal conditions, including inflammatory bowel disease, ulcers, diverticulosis, and other autoimmune diseases.
  • Checking for more polyps. If you’ve had polyps before, chances are higher you’ll have them again. A follow-up colonoscopy can detect new polyps, or make sure they were removed entirely.
Colonoscopy vs. endoscopy

An endoscopy and a colonoscopy are both nonsurgical procedures used to examine our digestive systems. Both involve inserting a flexible, thin tube into the body with a light and camera at the end.

What’s the primary difference between an endoscopy vs. a colonoscopy?
An upper endoscopy tube is inserted through the mouth, to examine the stomach, esophagus, and small intestine. A colonoscopy is performed through the rectum, to examine the rectum, colon, and large intestine.

How is a Colonoscopy Performed?


A colonoscopy procedure involves a thin, flexible colonoscope inserted into your rectum and guided up into the large intestine. The light and camera on the end of the colonoscope will allow your healthcare professional to examine the intestinal lining.

Here are six things to expect during the day of your colonoscopy:

  1. Arrive with a buddy. Since you will be given anesthesia, most medical facilities require you to bring a friend or family member with you to help escort you home.
  2. Prep with a nurse. After checking in, you’ll be taken to a private room and changed into a hospital gown. A nurse will check your vitals and review your medical history, allergies, and list of current medications.
  3. Prep for anesthesia. The nurse or an anesthesiologist will insert an intravenous (IV) line into your vein, with a port for the sedative.
  4. Meet with your doctor. You will talk with the doctor performing the colonoscopy. They can address any questions or concerns before you are taken to the procedure room.
  5. Lie down, take a nap. You’ll be instructed to lie on your left side on an exam table or rolling hospital bed. The nurse or anesthesiologist will administer the sedative through your IV port. The anesthesia is quick-acting and ensures you’ll have no discomfort during the procedure. Many people describe it as, “the best nap of your life.”
  6. Awake and recover. After about a half hour to an hour, you’ll awaken in a recovery room. A nurse may give you some juice and cookies or crackers. Once it’s determined you can stand and walk without feeling dizzy, you’ll be delivered to your buddy and escorted home.
How long does a colonoscopy take?

A colonoscopy procedure can take anywhere from 30 to 60 minutes. But when you factor in the waiting room time, check-in, prep, and recovery, the whole experience can take 3 to 4 hours. A female colonoscopy procedure may take a little longer than a male’s due to slightly longer colonic length.

Your doctor will let you know your colonoscopy’s initial findings on the procedure’s day.

Risks to Consider


A colonoscopy is considered a low-risk procedure, but some complications could develop.

Colonoscopy risks can include:

  • Injury to the colon lining, including a tear in the rectum or colon
  • Bleeding from the site where a polyp or sample tissue was removed
  • Infection in the case of perforation or bleeding
  • Adverse reaction to the anesthesia as some patients may have an abnormal response to the sedative

Preparing for a Colonoscopy


Your doctor will tell you how to prep for your colonoscopy. There are several colonoscopy preparation regimens to thoroughly cleanse your colon and rectum so the doctor can see the colon’s lining.

Here is what you can expect:

  • You will be modifying your normal diet for the few days leading up to your colonoscopy. This will involve restricting high-residue/high-fiber foods such as seeds, nuts, corn, and raw fruits and vegetables.
  • A week ahead of the procedure, make sure you have your bowel prep, clear liquids, wet wipes, and an adult escort prepared to take you home from the procedure. The adult escort does not need to stay the entire procedure. If you do not have a friend or family member who can do this, we can connect you with a service that can help.
  • When you begin the bowel preparation, you will be restricted to a clear liquid diet. Clear liquids include white grape juice, non-red or non-orange sports drinks, clear chicken broth, and ginger ale. Get these fluids ahead of time.
  • The evening before and on the morning of the colonoscopy, you will drink a laxative solution to flush all the stool out of your colon.
    • If you become nauseated as you consume the preparation, it is okay to slow down.
    • Refrigerating the preparation solution and drinking through a straw may help if you do not like its taste.
    • Stay close to your bathroom as you can expect to make frequent visits as you clear your bowels. Be sure to have enough toilet paper on hand. You should also have wet wipes and barrier cream to prevent chafing. The preparation process will likely take several hours.

What to Expect After a Colonoscopy

After the Procedure

Beyond being hungry, most people experience mild fatigue, grogginess, and constipation after a colonoscopy. It’s suggested that you don’t drive, operate machinery, or make any big decisions after the procedure.

Additional side effects after a colonoscopy can include:

  • Bloating
  • Gas pain
  • Nausea

Consult your doctor if you pass any blood or blood clots, have a fever, or experience persistent abdominal pain.


If polyps or tissue samples were found, or you underwent a diagnostic colonoscopy for intestinal issues, it can take 1 to 2 weeks to get the results of any biopsies taken.

  • A positive result from a colonoscopy screening is when a doctor finds any abnormal tissue or polyps. Not all polyps are precancerous or cancerous, but all polyps will be tested.
  • A negative result means no polyps or abnormal tissue was found. If you are considered at average risk for colon cancer, you may not need another colonoscopy for 10 years.



You must refrain from eating solid foods the day before a colonoscopy. Stick to Jell-O, clear juices (apple, white grape), popsicles, clear broth or bouillon, and clear sports drinks or sodas.

If the results from your first colonoscopy are negative, you should repeat the procedure every 10 years.

It’s best to avoid fatty or fried foods after a colonoscopy. Try eating pancakes, crackers, scrambled eggs, toast, soup, or other mild, non-spicy foods.

You should get a colonoscopy if your doctor recommends it, especially if you are experiencing intestinal issues, need a diagnosis for a GI disease, or are due for a colon cancer screening.

Most of your body is covered by a hospital gown and sheet.

It is recommended for most people to get a colonoscopy starting at age 45. People with a family history of colon cancer or certain intestinal issues should begin screening at age 40.

Get Care

Receive a Colonoscopy at NewYork-Presbyterian

NewYork-Presbyterian offers colonoscopies at numerous convenient locations in Manhattan, Brooklyn, Queens, Westchester, and the Hudson Valley. If your screening results require you to take further steps, our multidisciplinary teams of colorectal cancer experts will guide you—offering compassionate support and care.

A colonoscopy can provide early detection of colon and rectal cancer. Call NewYork-Presbyterian today to schedule yours.