Colonoscopy is a widely used test to screen for colon and rectal cancers. Preparing for a colorectal cancer screening may not be the most comfortable or convenient thing you’ll do, but it’s necessary for the test to be effective. And with new cases of early-onset colorectal cancer and colorectal cancer on the rise in people under the age of 50, quality colonoscopy screening is so important.

The more you know about what to expect can help take away some of the fear of having a colonoscopy and the preparation required for it. Here’s what to know before you go.

About Colonoscopy

A colonoscopy is a brief procedure done as part of your routine health care. The screening usually lasts from 30 to 60 minutes and is performed by a gastroenterologist to look at the inside of the entire colon (large intestine) and rectum. Not only can the screening test find colorectal cancers, but it can also prevent them.

“During a colonoscopy, abnormal growths known as polyps can be removed before they turn into cancer,” according to Yasser Jamal, M.D., a gastroenterologist at Texas Health Digestive Specialists, a Texas Health Physicians Group practice, and on the medical staff of Texas Health Fort Worth. “Prevention is certainly better than a cure. That’s why it’s an important test to have done to find those pre-cancerous polyps and remove them. Finding colorectal cancer early, when it’s small and hasn’t spread, often allows for more treatment options and better outcomes.”

The American Cancer Society recommends colorectal cancer screening for people at average risk starting at age 45. If you have certain risk factors that raise your chances of getting the disease, you may need to start screening at a younger age. Because colon cancer cases are on the rise in younger patients, Jamal suggests that any younger adult who is experiencing abdominal pain, rectal bleeding, changes in bowel habits, or iron deficiency anemia see a doctor and consider having a colonoscopy.

You likely won’t be awake to remember a colonoscopy because you’ll be given medicine to help you relax and sleep while it’s done. And because the instruments used to perform the exam are small, you should have few side effects. It’s the preparation for the procedure that most people consider to be the unpleasant part.

What to Expect Before the Exam

To have a successful colonoscopy, you must have a clean colon so your doctor can get a good sense of your colon health. This means following a modified clear-liquid diet free from fiber for at least 24 hours before the procedure.

“The prep may include avoiding solid foods, drinking a large amount of liquid laxative or taking an oral laxative, and/or sometimes enemas that make you go to the bathroom,” Jamal says. “You may also need to adjust or stop taking certain over-the-counter or prescription medications entirely for up to a week before the test.”

Although nothing by mouth the day of a colonoscopy is the general rule of thumb, Jamal adds that people with diabetes, high blood pressure, or heart problems, or those taking medications or supplements containing iron, should remind their doctors of everything they are taking well in advance of the procedure.

What to Expect After the Exam

When you wake up after your colonoscopy, you shouldn’t experience much pain. You may, however, feel some cramping or discomfort from the air that was puffed into the colon during the test. Air is used to keep the colon open for the doctor to examine it.

“You may have a little bloating and occasionally some light bleeding if large polyps are removed,” Jamal notes.

A colonoscopy is considered negative if no abnormalities are found in the colon.

What Happens if Something is Found?

If a small polyp(s) is found during a colonoscopy, the gastroenterologist will probably remove it during the procedure. If a polyp is too large to be removed, or if it looks abnormal, a small piece of it will be taken out (biopsied) to check for cancer or precancerous cells. The results of this tissue analysis will help determine whether you need additional procedures or treatment.

If nothing is found and you are in good health, the American Cancer Society says you can go up to 10 years without another colorectal cancer screening. For people ages 76 through 85, the decision to be screened may be based on personal preference, life expectancy, overall health, and prior screening history as discussed with a health care provider. People over age 85 no longer require screening. If something is found, however, you may need more frequent tests or treatment.

Why Choose Colonoscopy?

Colonoscopy is the gold standard in colon and rectal screening. However, fecal testing with Cologuard and other means, virtual colonoscopy, and video capsule colonoscopy may be a good option for some people who are unable or not willing to undergo a colonoscopy.

“It’s important to realize that these types of non-invasive colorectal screenings are good for diagnosing cancer but not for preventing it and finding polyps,” Jamal reiterates. “Non-invasive testing should not be used for people in high-risk groups, or those with a previous history of cancers or colon polyps, rectal bleeding, changes in bowel habits, iron deficiency anemia, ulcerative colitis, or Crohn’s disease.

We know that about 80 percent of small polyps and about 60 percent of large polyps are missed with the noninvasive tests. Colonoscopy is ultimately about saving lives.”

Texas Health offers a network of digestive health specialists to help assess and treat colon and rectal cancers. Find a gastroenterologist near you at TexasHealth.org or take our colorectal cancer assessment to learn more about when you should be tested for colorectal cancer.