Frequently Asked Questions about Colonoscopy

Important reminder: This general information is for educational purposes only – it is not a definitive basis for diagnosis or treatment. It is very important that you consult your doctor about your specific condition.

Q. Are there any videos about what to expect with a colonoscopy exam? Watch and learn: You can access a number of patient education videos about colonoscopy and other tests at the website for The American Society for Gastrointestinal Endoscopy (ASGE). Or view a video showing how a colonoscopy is performed.

Q. What is a colonoscopy? A colonoscopy is an examination that enables your doctor to examine the lining of your colon (large intestine). The doctor will take a flexible tube about the size of a finger and slowly move it into the rectum and through the colon to look for signs of cancer or pre-cancerous lesions.

Q. What are the symptoms of colon cancer? Often, the early stages of colon cancer do not have symptoms. That is why preventive screening is very important. Every year, millions of adults help prevent the development of colon cancer by having a routine colonoscopy. During a colonoscopy, when doctors find pre-cancerous growths called “polyps,” they can easily remove the polyps – greatly lowering your risk of developing colon cancer. Symptoms can include rectal bleeding, anemia, a change in bowel habit, abdominal pain and weight loss, but these symptoms are common for other illnesses as well. When the symptoms are caused by cancer, the disease may be in a late stage.

Q: Are there different types of polyps? There are two types of polyp shapes and five types of polyps. Visit our Colon and Rectal Polyps page to learn more.

Q: What is a complex polyp? In general, a rectal or colon polyp is considered complex (also known as “defiant”) if it meets any of the following criteria:

  • Size greater than 2 centimeters
  • Located in a difficult area or is too flat (sessile) to be removed during a standard colonoscopy
  • When the doctor performing your colonoscopy does not feel they can safely remove the polyp(s) and decide to refer you to a specialist

Q: Is surgery the only option for complex polyp removal? If the complex polyp is benign, with no signs of cancer present, then the patient may choose non-surgical removal instead of surgery; however, this requires the expertise of a highly skilled physician who has performed a large volume of these procedures.

Q. Who is at risk of colon cancer? Age is the No. 1 risk factor – more than 90% of colon cancer cases occur in people (men and women equally) age 50 and older. There are other risk factors:

  • Family history of colorectal cancer or adenomas (polyps)
  • Cigarette smoking – which can increase the risk of colon cancer death by 30% - 40%, possibly accounting for up to 12% of colon cancer fatalities
  • Obesity
  • Sedentary lifestyle
  • High-fat diet, especially one from mostly animal sources
  • Heavy alcohol intake
  • Ulcerative colitis or Crohn's colitis
  • Cancer of the uterus or ovaries before age 50
  • Past removal of the gall bladder
  • Past radiation therapy of the abdomen
  • Diabetes – which can increase the risk of developing colorectal cancer 30% - 40%

Q. Who should be screened and when? The American Cancer Society recommends that adults be screened for colon cancer beginning at age 50 – or even earlier if there is a family history of the disease.

Q. Will I receive sedation for the exam? You will receive “conscious sedation” for the exam, which means that an intravenous line is placed, and medications are given intravenously. This is not general anesthesia, although almost all patients are comfortable during the procedure. Because of the sedation, you will need a driver to take you home.

Q. Do I need a referral? If you have an HMO type of health insurance, you will need a referral from your primary care provider. Check with your health insurance provider.

Q. Does my insurance cover this procedure? You should check with your health insurance provider to determine your colorectal cancer screening benefits. Most insurance providers cover colonoscopy for colon cancer screening; however, insurance coverage varies.

Q. What do I need to do to prepare for a colonoscopy? Preparation is a critically important part of the exam. If your bowel is not adequately cleaned out before the exam, the doctor will not be able to identify polyps, the pre-cancerous lesions. Before the procedure, you will have to take an oral laxative solution (called “a bowel prep” or “preparation”) to clean out your bowel. Specific prep instructions vary, but the prep usually begins 1 to 2 days before your procedure. Please read your prep instructions (given separately) to understand what you should do 1 day or 2 days before your colonoscopy.

Q:  I am menstruating.  Can I still have a colonoscopy?  Yes, the procedure can still be performed while you have your period.  Tampons can be worn if preferred by the patient.

Q:  If a patient has a fever will a colonoscopy still be done? In general no.  A colonoscopy will not be performed if a patient has a temperature over 101 degrees.  Please contact your physician and let them know as soon as possible.

Q. Are there any complications or risks associated with having a colonoscopy? In general, colonoscopy is a safe procedure. As with any medical procedure, however, there are some risks associated with the procedure and with the sedation used. You should contact your doctor if you feel severe abdominal pain, dizziness, fever, chills or rectal bleeding after the colonoscopy. Perforation and bleeding are two of the major complications associated with colonoscopy. Perforation is a tear through the wall of the bowel that may allow leakage of intestinal fluids. Perforations are generally treated with hospitalization, antibiotics, and possible surgery. There may be bleeding at the site of a biopsy or polyp removal. Most cases of bleeding stop without treatment or can be controlled at the time of the procedure. Rarely, blood transfusions or other treatments may be required to stop the bleeding. There also is a risk of having a reaction to a sedative given during the exam. In most cases, medications are available to counteract this reaction. Although complications after colonoscopy are rare, they can be serious and life-threatening. It is important for you to be aware of early signs that something might be wrong.

Q. If I take medication, are there any risks? In general, most medications do not interfere with this procedure. However, if you are on insulin, your dosage may need to be adjusted – or changed – for the preparation period and the day of the exam. Also, if you take anti-coagulant or blood-thinning medicines, they will have to be stopped (and be possibly started on a bridge medication) before the procedure to allow for biopsy and/or polyp removal. Ask your physician about adjusting your medication.

Q. How long does the procedure take? How long will it take for me to recover? The procedure itself usually takes from 15 to 60 minutes, but you should plan on spending 2 to 3 hours total to account for preparation, waiting and recovery time.

Q. How many days do I need to take off work? You will need to take off work the day of the procedure. Some patients who work evenings also take off work the day before the procedure to do the bowel prep.

Q. Where can I get a colonoscopy at U-M? We have state-of-the-art colonoscopy facilities at:

Q. Are there different options for colon cancer screening? Currently, screening guidelines include a choice of four different tests:

  • Colonoscopy. Colonoscopy is the “gold standard test,” which means we believe it is most effective in detecting cancer and precancerous lesions. An instrument is inserted into the colon through the rectum. The rectum and entire colon are examined using a lighted instrument called a colonoscope. During colonoscopy, precancerous and cancerous growths throughout the colon can be found and either removed or biopsied. An advantage of having a colonoscopy is that growths in the upper part of the colon, where they would be missed by sigmoidoscopy, can be detected or found.
  • A Fecal Immunochemical Test (FIT), or Fecal Immunochemical Occult Blood Test, is a home stool test that is used to look for possible signs of colorectal cancer. FIT looks for a specific type of blood in the stool, which helps determine if a person has any polyps (growths of tissue) in the colon. 
  • Stool DNA testing (Cologuard). This test identifies DNA mutations from colon cells that are excreted in stool samples. As part of the stool DNA testing, a fecal immunochemical test is also routinely performed.  Stool DNA testing will detect colorectal cancer approximately 92 percent of the time and advanced polyps approximately 42 percent of the time.  A follow-up colonoscopy will be scheduled if the test yields a positive result.  Stool DNA testing should be repeated every 3 years.   
  • Flexible sigmoidoscopy. In this test, the physician examines the rectum and lower colon using a lighted instrument called a “sigmoidoscope.” During sigmoidoscopy, precancerous and cancerous growths in the rectum and lower colon can be found and biopsied. If the physician discovers a polyp, the patient will need to have a colonoscopy at a later date. Studies suggest that regular screening with sigmoidoscopy after age 50 can help reduce the number of deaths from colorectal cancer. A thorough cleansing of the lower colon is necessary for this test.  If the test yields a positive result, a follow-up colonoscopy will be scheduled

Q. Is there anyone who should not have the procedure? Colonoscopy is not recommended in pregnant patients, patients 75 years or older, patients with limited life expectancy, or in patients with severe medical problems making them high risk for sedation.