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A colonoscopy is an exam that lets your physician see your entire colon. Before the test, your health care team will give you instructions for how to clear your colon of any stool. This process is called bowel prep. For the test, you’ll be given a drug to help you relax and be comfortable (sedative). The physician will put a thin, flexible tube called a colonoscope into your rectum to look inside.
The colonoscope has a tiny camera on the end that lets your physician view your colon on a screen. This way, they can check for anything that’s not normal. They look for polyps (which may or may not be cancer), tumors and other abnormal tissue. If the physician finds anything, they can remove it and send it to a lab for testing (biopsy) to see if the cells are cancer.
At-home screening tests for colon cancer include fecal immunochemical test (FIT) and guaiac-based fecal occult blood test (gFOBT) as well as Cologuard.
Schedule Your Screening
Talk to your primary care provider about colorectal cancer screening. UW Medicine Primary Care can help you get started with screening. You may be referred for a colonoscopy or a different screening test. Learn about Fred Hutch's relationship with UW Medicine.
If you need a colonoscopy, call 206.606.5342 to schedule your procedure at Fred Hutch Cancer Center – South Lake Union.
Colonoscopies for Colon Cancer Screening
Physicians use colonoscopies to:
- Screen for polyps and colon cancer in people without any signs or symptoms
- Investigate signs or symptoms that might come from polyps, cancer or another condition
- Get more details if another screening test (like FIT, gFOBT or Cologuard) showed there might be polyps or cancer
- Prevent colon cancer by taking out polyps before they have a chance to turn into cancer
- Diagnose colon cancer by testing tissue that was removed
- Treat colon cancer by taking out cancerous polyps or other small cancers
The U.S. Preventive Services Task Force recommends colorectal cancer screening — using colonoscopy or another method — for all adults starting at age 45. After age 75, the task force recommends talking with your health care team to decide if you still need screenings. If a colonoscopy shows everything is normal, the usual schedule is to repeat it again in 10 years.
If you are at high risk for colon cancer, you may need to start screenings before age 45 or have them more often. Ask your primary care provider, and learn more about colon cancer risk factors.
Colonoscopy Screening Results
Flexible Sigmoidoscopy Screening
A flexible sigmoidoscopy is like a colonoscopy, except it looks at only the lower part of the colon and the rectum. A colonoscopy looks at the entire colon. You need to do bowel prep, but it’s not as intensive as it is for a colonoscopy. Most people don’t have sedation, like they do for a colonoscopy. The physician can still remove polyps or other abnormal tissue they see. One possible benefit of sigmoidoscopy is it might be offered in some places where it’s harder to find a provider to do a colonoscopy.
If the sigmoidoscopy finds a problem, you will need a colonoscopy to look at the rest of your colon. If the sigmoidoscopy doesn’t find any problems, the usual schedule is to repeat it every five years.
Virtual Colonoscopy (CT Colonography) Screening
Virtual colonoscopy is another way for your physician to see inside your colon. It can be used to look at the whole colon from the top down to the rectum. It doesn’t involve inserting a scope, but a small tube will be used to pump air into your colon. Then you’ll have a computed tomography (CT) scan. CT uses X-rays to make pictures of the inside of the body. Like with a colonoscopy, you need to do bowel prep to clean out your colon before the scan. You don’t need to be sedated.
If the virtual colonoscopy finds a problem, you will need a true colonoscopy to get more detail and maybe remove polyps or other abnormal tissue. If the virtual colonoscopy doesn’t find any problems, the usual schedule is to repeat it every five years.
Why Choose Fred Hutch for a Colonoscopy
Together, Fred Hutch Cancer Center and UW Medicine offer a full range of screening options to reduce the risk of colorectal cancer or to find it at its earliest stage. If you need a colonoscopy, we offer this procedure at Fred Hutch Cancer Center – South Lake Union.
Along with treating colon cancer, our expert gastroenterologists do colonoscopies to screen for, prevent or diagnose the disease. We have an experienced team who will help you prepare and walk you through the procedure step by step. When your results are ready, we’ll explain what they mean and what to do next.
CT colonography (virtual colonoscopy) is offered at UW Medical Center.
Each type of colon cancer screening has advantages and disadvantages. A colonoscopy may or may not be the best test for you. To decide, it’s a good idea to talk about the options with your primary care provider. Here are some of the things to consider about having a colonoscopy:
- You may need to make changes to your diet or medicines in the days before the test.
- It is an invasive procedure.
- You need to prepare by cleaning out your colon in advance.
- You will be sedated for the test (given medicine to help you relax and be comfortable).
- If you are at average risk and your results are clear, you will probably not need to repeat the exam for 10 years.
- If the physician finds something abnormal, they can take out tissue during the exam.
- There’s a small risk of tearing or going through the lining of the colon.
In the day or two before your colonoscopy, you will need to follow a special diet. This usually means drinking clear liquids like water, broth or clear juices and avoiding solid foods. You will also need to take a bowel prep solution to empty your colon. So, it’s important to stay near a bathroom. You may need to take laxatives or stool softeners.
When you make your appointment, your care team will give you detailed instructions on how to get ready for a colonoscopy. Proper prep helps clear your colon of any stool and makes the exam much more accurate. Follow the instructions carefully. If you don’t, you may need to reschedule your appointment and start the process all over again.
You may also need to stop taking certain medicines before the test. Your care team will let you know.
For the procedure, you’ll get a sedative that will help you relax and be comfortable. So, you won’t be allowed to drive afterwards. Plan ahead of time for a friend or family member to drive you home.
During a colonoscopy, you’ll be given a sedative. Afterward, you will rest until the sedative wears off. This usually takes about an hour. You might feel weak or groggy, so ask the person driving you home to help you get into and out of the vehicle.
No, colonoscopies do not hurt. Most people feel no discomfort. You may have mild bloating or cramping afterward, which usually goes away quickly.
A physician does a colonoscopy. Usually, this is a gastroenterologist.
A colonoscopy usually takes 30 to 60 minutes. Afterward, you will rest for about one hour until the sedative wears off.
If your physician sent tissue samples to the lab for a biopsy, it will probably take a few days to get the results, sometimes longer. Ask your care team how you’ll get the results and how long it will take.
After a colonoscopy, most people can return to normal activities or work the next day.