Can I do a stool test at home instead of a colonoscopy?

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Q: My doctor always encourages me to do a colonoscopy for colorectal cancer screening. But I have friends who just do a stool test at home, which seems easier. Why should I go through the hassle of a colonoscopy?

A: My maxim is that any cancer screening is better than no cancer screening. Colorectal cancer is one of the leading causes of cancer death in the United States, and cases are occurring with increasing frequency among younger people. It scares me that 28 percent of U.S. adults are not up to date with screening. If stool tests help close that gap, I’m all in.

Modern kits that test your stool for abnormal DNA and microscopic quantities of blood can detect around 92 percent of colorectal cancers. Completing a stool test is a very streamlined process, which you can do entirely at home.

So why the hype around colonoscopies? The reason is not simply because colonoscopies are also a great screening tool: The procedure identifies about 95 percent of colorectal cancers. It’s because colonoscopies prevent colorectal cancer. They can reduce new cases of colorectal cancer by as much as 69 percent and death from colorectal cancer by as much as 88 percent.

This happens because colonoscopies involve a trained gastroenterologist looking inside your colon. They hunt for polyps – small, abnormal growths – hiding in your gut, and if they see one, they can remove it right away. Nearly all colorectal cancers start as polyps. So when you get a colonoscopy, you’ll be screened for cancer – but you’ll also get the precancerous growths taken out of your body.

This is very different from tests that merely detect problems that are present and growing. The stool kits that look for blood and abnormal DNA do detect some polyps that have traveled further along the path toward officially becoming cancer – picking them up anywhere between around 40 and 70 percent of the time. They’ll likely miss the ones in earlier stages though. Also, if a stool test is positive, the next step is – surprise: a colonoscopy.

The U.S. Preventive Services Task Force recommends adults start colorectal cancer screenings at age 45. Those with a high-risk history, like inflammatory bowel disease or a family history, may be advised to start sooner.

For me, undergoing one half-day procedure every seven to 10 years (which is the usual screening interval for a colonoscopy if everything looks normal) is worth the peace of mind. It’s also why stool tests are recommended to be done more frequently than colonoscopies – to try to minimize the chance of a new cancer drastically spreading between screenings.

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Which stool test should I get?

You and your doctor will decide on the best stool test for you. There are a few options:

Fecal immunochemical testing (FIT), which detects blood from the GI tract. You could get a FIT test on your own over-the-counter, online or through your doctor. For some FIT tests, you’re given a long-handle brush or small probe to collect stool directly from your toilet bowl. These tests pick up about 74 percent of colorectal cancers. They are usually done once a year.

Cologuard, which looks for blood as well as abnormal DNA. Cologuard requires a prescription. With Cologuard, you’ll find a small collection bucket that attaches to your toilet bowl. This test detects about 92 percent of colorectal cancers. It is recommended to be repeated every three years.

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How should I collect a stool sample?

After you order the stool test, it’ll arrive in a box at your doorstep. Hold off on collecting a sample if you’re on your period or have an actively bleeding hemorrhoid. And don’t pee at the same time. Your sample should contain but one thing only.

Be sure to follow the instructions in your kit. You should mail your sample that same day (shipping is prepaid). If you can’t send it in until the next day, you might have to keep the sample in the fridge – don’t panic, it’ll be fully sealed!

After the company receives your stool, depending on which test you’re using, your physician will be sent a result within days to up to two weeks. Both tests are fully covered by most major commercial insurance companies as well as by Medicare and Medicaid.

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Who shouldn’t get a colonoscopy?

Colonoscopies are generally very safe, but they aren’t perfect – the procedure carries small risks including possible tears in your gut or an infection. To find out if you’re a good candidate, ask yourself the following questions:

— Are you able to do a stool prep? Let me start by saying that the “prep” – or the cleansing of the bowels required before a colonoscopy – is a much better experience today than whatever you’ve heard from your dad. Newer options don’t involve drinking four liters of medication, and there are even pill-based preps available. But if you struggle with mobility and are going to have a tough time getting up to go to the bathroom multiple times, doing a bowel prep can become a big issue. Pro tip: People who are constipated at baseline or those who are on medications like Ozempic, which can slow down the gut, should discuss doing a lengthier bowel prep with their provider.

— Can you undergo anesthesia? This is not a firm requirement per se. You can request to do your colonoscopy without anesthesia. But most people in the United States choose to get anesthesia as it makes the procedure much more comfortable. People with advanced heart or lung conditions may not be good candidates for certain forms of anesthesia and should discuss options with their provider. If you do get anesthesia, keep in mind that you’ll need to miss at least about half a day of work and shouldn’t operate heavy machinery for the rest of the day. You’ll also need a friend or family member to give you a ride home (clinics and hospitals tend to have a policy that won’t allow you to use an Uber or taxi).

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What I want my patients to know

There are many people who may want the benefits that a colonoscopy can offer but realistically cannot make these requirements work. In these cases, please don’t skip screening entirely – do a stool kit. On the other hand, people who are at higher risk of colorectal cancer should opt for the colonoscopy. And if neither of these work for you, we’ve still got options: There are actually other ways to screen for colorectal cancer, including a special kind of CT scan or a procedure called a flexible sigmoidoscopy that doesn’t involve the same overnight prep as a colonoscopy. Talk to your provider about which one is the right choice for you.