Colonoscopy

A colonoscopy is the method of choice to screen for colorectal cancer. It a long, flexible tube with a camera on the end. It is advanced from the rectum all the way to the beginning of the colon. The entire lining of the colon and rectum are then visualized as the colonoscope is withdrawn. The major benefit of a colonoscopy is that if a polyp or lesion is seen it can be removed or biopsied to diagnose a suspected polyp or cancer

The first step of a colonoscopy is the preparation or cleansing of the colon. The night before your procedure, you cannot eat or drink after midnight. For an afternoon procedure, you cannot eat or drink for 8 hours before the procedure.

Once you arrive at the procedure center, you are checked by the nurses and physicians and an IV is started. When the pre-procedure checklist is completed, you are brought to the colonoscopy suite. The anesthetist attaches oxygen and the heart monitor. Sedation is given once you are placed on your left side. The colonoscope is passed per anus into the rectum and advanced to the beginning of the colon.

To advance the scope, air or gas is instilled into the colon to distend it. This allows for navigation through the colon and flattens out the folds so that a thorough exam can be performed. After completion of the procedure, you are taken to the recovery room to wake up. Once awake you are given something to eat and drink. When you are fully awake, you are allowed to go home.

Patients feel pain when the colon is distended or stretched.  During the procedure, the colon is stretched as the colonoscope advances, and distended with gas to examine it.  To help the scope advance, pressure may be applied to your abdomen. This can cause some mild discomfort.  You should not feel any pain during the procedure as a result of the anesthesia. The majority of discomfort is gone within 15 minutes after the exam.  By the time you are ready to go home, you should not have any pain.

The time from your arrival to departure is typically two hours. The pre-procedure process takes about 30 minutes, the colonoscopy procedure itself takes 30-45 minutes, and recovery takes about 30 minutes.

The time from your arrival to departure is typically two hours. The pre-procedure process takes about 30 minutes, the colonoscopy procedure itself takes 30-45 minutes, and recovery takes about 30 minutes.

The quality of the colonoscopy exam is directly related to how well the colon is cleansed of any residual stool.  Therefore, the preparation is one of the most important aspects of the exam.  It is also the most challenging.

Depending upon your bowel habits and diet, it may be beneficial to modify your diet with low-residue foods for a couple of days prior to starting the laxative.  Low residue foods include things such as chicken, turkey, pasta, eggs, fruit and vegetables without the skins.

The day before the procedure, the hard work begins.  On this day, you cannot eat any solid food and you can only drink liquids.  You can drink any liquid without dairy or milk, including coffee or tea.  Consuming an adequate amount of liquids will help manage the hunger pains and prevent dehydration.  Refrain from drinking anything red, as this can be confused for blood at the time of the colonoscopy.

There are several options available for the purging process.  The most commonly regimen prescribed is the split prep.  Half of the prep is consumed the day before and the second half is taken 6 hours before your exam.  Around 5 pm the night before your procedure, empty the first bottle of the prep into a container and add 16 oz of chilled water. Once completed, consume an additional two 16 oz glasses of water.  Ideally, all of this should be completed within an hour. The second bottle of the prep is consumed in the same fashion roughly 6 hours before your exam.  Results from the prep may vary but typically are expected within 1-4 hours after drinking each bottle.

Nausea is a very common side effect of the preparation used for purging the colon.  The solution is high in sulfate salts, so it has a bitter, salty taste.  Mixing the solution with a sports drink or flavored drink powder and drinking it chilled can help improve the taste.  Take your time drinking the solution.  Typically, the faster you drink it, the more difficult it becomes.  Many physicians will prescribe ondansetron, an anti-emetic, to take with the solution to help minimize nausea.

The frequency of colonoscopy is dependent upon your personal and family history of polyps or cancer.  Typically, screening for colorectal cancer should begin at age 50.  There are circumstances that screening should begin at age 45, so speak with your doctor if you have questions.  

• For patients with average risk of Colorectal cancer (no symptoms, personal or family history)
  • 10 year interval
    • No family history of colorectal cancer
    • Normal colonoscopy
  • 5 year interval
    • No family history of colorectal cancer
    • Polyps found on colonoscopy
      • 2 or fewer polyps
      • The polyps are <5mm in size
      • Tubular adenomas
  • 3 year interval
    • No family history of colorectal cancer
    • Polyps found on colonoscopy
      • 3 or more polpys
      • A single polyp >10mm in size
      • A single polyp with villous histology
      • Polyp with high grade dysplasia
• For patients with a family history of colorectal cancer
  • Family member is <50 years of age 
    • Begin screening 10 years before the family member was diagnosed
    • Screen every 2-3 years
  • Family member is >50 years
    • Begin at age 45 years or 10 years before family member was diagnosed (whichever comes first)
    • Screening interval 3 years

Colonoscopy remains the gold standard for detection of colon and rectal cancer. It is the best test available for screening, and is also therapeutic because of the ability to remove or biopsy polyps at the time of screening. 

Colonoscopy does require more work and prep than other tests, which is often perceived as the major barrier to patients getting the exam.  There are several stool-based tests, but these must be done more frequently.  These tests include the highly sensitive fecal immunochemical test (FIT) and guaiac-based fecal occult blood test (gFOBT), both of which must be done annually, and the multi-targeted stool DNA test (such as Cologard), which must be done every 3 years. The other drawback of these tests is that a positive test result requires a colonoscopy.

Washington University Colorectal can provide options for a colonoscopy. Meet our specialists below. 

Kerri Ohman, MD

Paul Wise, MD

Steven Hunt, MD

Matthew Silviera, MD

Matthew Mutch, MD