A colonoscopy is one of the most effective tools we have for detecting and preventing colorectal cancer. Many people have questions about colonoscopy, such as how it works, does it hurt, how long it takes, and how to prepare.
At WashU Medicine, our colorectal experts perform this procedure with precision and care, helping patients stay ahead of potential health issues.
What is a colonoscopy?
A colonoscopy is a diagnostic procedure used to examine the inner lining of the colon and rectum. Using a long, flexible tube equipped with a camera (called a colonoscope), your doctor can view the entire colon and identify any abnormalities such as polyps, lesions, or signs of cancer.
One of the key benefits of a colonoscopy is that polyps can be removed or biopsied during the procedure, making it both diagnostic and therapeutic.
More info: Colonoscopy>>
Did you know?
Colonoscopy can detect and remove polyps, making it possible to prevent colorectal cancer, if polyps are caught early.
How is a colonoscopy performed?
The process begins with colon preparation, which is essential for a successful exam. Patients follow a special diet and take a prescribed laxative solution to cleanse the colon. This ensures the doctor has a clear view during the procedure.
On the day of the colonoscopy:
- You’ll be checked in and an IV will be started.
- Sedation is administered to keep you comfortable.
- You’ll lie on your left side while the colonoscope is gently inserted through the rectum and advanced through the colon.
- Air or gas is introduced to expand the colon, allowing the scope to navigate and flatten folds for a thorough examination.
- The scope is then slowly withdrawn while the doctor examines the lining and removes any polyps if necessary.
After the procedure, you’ll be monitored in a recovery room until you’re fully awake. Most patients are ready to go home within two hours of arrival.
Does it hurt?
Thanks to sedation, most patients do not feel pain during the procedure. Some may experience mild discomfort from the air used to expand the colon or from pressure applied to the abdomen to help guide the scope. This discomfort typically resolves quickly—often within 15 minutes after the exam.
How long does it take?
From check-in to discharge, the entire process usually takes about two hours:
- 30 minutes for pre-procedure prep
- 30–45 minutes for the colonoscopy itself
- 30 minutes for recovery
The exact timing can vary depending on certain factors. Ask your doctor how long you should expect the colonoscopy to take for an accurate time estimate.
Preparing for your colonoscopy
Preparation is key.
A few days before the procedure, patients may be advised to follow a low-residue diet (e.g., chicken, pasta, eggs, peeled fruits and vegetables).
The day before, only clear liquids are allowed—no solid food. Avoid red-colored drinks, which can be mistaken for blood during the exam.
The most common prep method is the split-dose regimen, where half of the laxative solution is taken the evening before and the other half six hours before the procedure. Nausea is a common side effect, but mixing the solution with flavored drinks and drinking it chilled can help. Your doctor may also prescribe anti-nausea medication.
While these are general guidelines, make sure to follow any prep instructions as provided by your doctor.
Why is it important?
Colonoscopy is the gold standard for colorectal cancer screening. It not only detects cancer early but also prevents it by removing precancerous polyps. Screening typically begins at age 45, but earlier or more frequent exams may be recommended based on personal or family history.
Learn more about the signs of colorectal cancer>>
Is it time to schedule your colonoscopy?
If you’re due for a colonoscopy or have questions about your colorectal health, our team at WashU Medicine is here to help.
Talk to your doctor or call us to learn more: 314-454-7177