Good news: Only three require some form of bowel prep.

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Colorectal cancer screening has long been something most adults happily put off until they turn 50—but now that colon and rectal cancers are on the rise in those under 50 years old, some health agencies are suggesting that screenings for the disease start earlier.

The American Cancer Society (ACS) did just that—in 2017, after reporting a dramatic uptick in colorectal cancer cases in younger adults, the ACS suggested testing for the cancers should begin at age 45 rather than 50 for people at average risk of the disease.

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Credit: Getty Images

The Centers for Disease Control and Prevention (CDC) and the US Preventive Services Taskforce, however, maintain that colorectal screenings may continue to begin at age 50, as long as the person is of average risk for the disease. People may stop those regular screenings at the age of 75, and then after the age of 85 no one needs colorectal cancer screenings, per the ACS.

Those who should begin colorectal cancer screenings before the age of 50 or 45 are people with an increased risk of being diagnosed with the disease, like those who have the following: a family history of colorectal cancer, a personal history of colorectal cancer or polyps, a personal history of inflammatory bowel disease (IBD, either Crohn's disease or ulcerative colitis), certain genetic conditions (familial adenomatous polyposis or hereditary non-polyposis colorectal cancer), or a history of radiation to the abdomen or pelvis, per the ACS.

But even if you haven't hit the typical age when screenings start, or don't have any factors that could increase your risk of the disease, it's imperative to stay aware of your body and to bring any alarming colorectal cancer symptoms to your doctor immediately. Those include signs like blood in your stool, unexplained stomach cramps, weight loss, or changes in your bowel habits.

Regardless of why you're getting screened for colorectal cancer, it's important to know what you're getting yourself into. Here's what you need to know about your colorectal cancer screening options—and who should get what kind.

Types of colorectal cancer screening tests

If a colorectal cancer screening test conjures up images of colonoscopies and bowel prep strategies, you may be able to breathe a sigh of relief: The US Preventive Services Task Force actually outlines six different screening options—and three of them don't include any type of out patient procedure at all.

Stool tests

The CDC lists three different stool tests that can be used for colorectal cancer screenings—something that could lead to more people getting screened for colorectal cancer overall. "If we give patients a choice and let them factor in what's available to them, then maybe those things will contribute to higher adherence and therefore greater practical impact of the screening recommendation," Nancy You, MD, an associate professor in the Department of Surgical Oncology at the University of Texas MD Anderson Cancer Center, tells Health.

Those stool-based tests include: the guaiac-based fecal occult blood test (gFOBT), which uses a chemical called guaiac that can detect blood in your stool; the fecal immunochemical test (FIT), which also can detect blood in your stool, this time through the use of antibodies; and the FIT-DNA test, which is part-FIT, part DNA test that can detect altered DNA in your stool.

Both the gFOBT and FIT tests only require you to collect small sample of stool, which is then sent to a lab. They're meant to be done once a year. The FIT-DNA test, on the other hand, requires you to collect an entire bowel movement, but only needs to be done every three years.

Here's the thing about stool-based tests though: They may be easier to do, but if you get a positive (or even inconclusive) result, you will still have to get a colonoscopy done, according to the ACS. And these less invasive tests aren't recommended for those with a higher risk of developing colorectal cancer.

Flexible sigmoidoscopy

Think of a flexible sigmoidoscopy as a less intense version of a full-blown colonoscopy. A doctor will use a short, thin, flexible tube into your rectum to check for polyps or cancer— but only inside the rectum and lower third of your colon.

A flexible sigmoidoscopy is often preferable to a colonoscopy because they may take less time and may not require anesthesia, per the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). It may also let you avoid a complete bowel prep, per the ACS, but that's entirely up to your doctor performing the procedure. It's recommended that a flexible sigmoidoscopy is done every five years, or every 10 years in addition to an FIT stool test each year.

As with stool tests, if your doctor detects abnormalities in your flexible sigmoidoscopy, you will likely need another full colonoscopy to check the rest of your colon. A flexible sigmoidoscopy is less recommended for those with a heightened risk of colorectal cancer.

CT colonoscopy

A computed tomography (CT) colonoscopy is a type of virtual colonoscopy—that means it uses X-rays and computers to show doctors your entire colon, without physically inserting a scope into your body.

This option is still pretty new, which means that it may not be available via your gastroenterologist, and if it is, insurance may not cover it. This may seem like the easier route—you don't need sedation, and it shows your entire colon on a screen—but you will still have to do a full bowel prep for the procedure. If your doctor sees a polyp or anything else abnormal, you'll also need to have an additional colonoscopy done to further test for cancer. A CT colonoscopy can be performed every five years, as long as you continue having clear results.

Colonoscopy

A colonoscopy is the gold standard for colorectal cancer screenings. During the procedure, doctors will insert a long, thin, flexible tube into your rectum and throughout your entire colon to check for polyps or cancer. If a doctor does find something abnormal during a colonoscopy, they can quickly remove the polyp or tissue sample to test for cancer. You will likely be under anesthesia for the procedure, and may also miss a day of work for recovery.

A colonoscopy brings an added element of discomfort: bowel preparation. According to the American Society for Gastrointestinal Endoscopy, there are different types of bowel preps (your doctor will prescribe the one best for you and your situation), but it will generally include a diet limited to clear fluids for at least one day before your colonoscopy. Along with a change in diet, you will also receive a prescription for medication that will more thoroughly cleanse your colon of waste.

Is it uncomfortable? Sure, but it's the best way for your doctor to thoroughly examine your colon and not miss any precancerous growths or other abnormalities. If your colon isn't as clean as your doctor would like, they may make you do it all over again, so you may as well do it right the first time to sidestep that.

A colonoscopy is recommended for those who have a higher risk of colorectal cancer, regardless of their age. For those who are at an average risk of the disease, colonoscopies can be performed every 10 years.

Talk to your doctor to help you determine which colorectal cancer screening method is right for you and to get the details on how often to screen, which, again, varies by test. You'll also need to check which tests your insurance will cover.

And in addition to screening for colorectal cancer, it's also important to do all you can to take healthy steps that might lower your lifetime colorectal cancer risk, such as cutting back on red meat and alcohol, eating plenty of high-fiber produce, getting regular exercise, maintaining a healthy weight, and quitting smoking if you haven't already.

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