Ryan Reynolds lost a bet and had to film his first colonoscopy

After losing a bet with a friend, Ryan Reynolds filmed his first colonoscopy and doctors made what they called a potentially life-saving discovery during the procedure.

The YouTube video was shared Monday in collaboration with the campaign Lead from Behind, which seeks to raise awareness about colorectal cancer and significantly increase the number of people who get screened.

Reynolds made the wager with fellow actor Rob McElhenney, who is also his co-owner of the Welsh soccer team Wrexham AFC.

"At the heart of all sports is competition," Reynolds says at the beginning of the video. "Rob and I think we're pretty competitive guys."

Reynolds feigns a lack of recollection of the terms of the wager that led to the video, and McElhenney explains it. He does so speaking in Welsh, which Reynolds bet him he would not be able to learn.

Both men turned 45 this year, the age at which it is recommended that people who are otherwise healthy should start getting colonoscopies in the U.S.

"I would never normally have any medical procedure put on camera and then shared," Reynolds says. "It's not every day you can raise awareness about something that will most definitely save lives, that's enough motivation for me to let you in on a camera being shoved up my ass."

The video shows Reynolds entering a hospital in New York and meeting with a doctor who explains that the procedure takes roughly 30 minutes and is "stunningly effective."

And that definitely seems to have been the case for Reynolds' case. In recovery, looking woozy and quipping about his IV being filled with Aviation gin, the doctor delivers the results. He tells Reynolds that the scan found an "extremely subtle polyp" that he was able to remove.

"This was potentially life-saving for you, I'm not kidding. I'm not being overly dramatic," he tells Reynolds.

"This is exactly why you do this."

McElhenney also shared video of his procedure, during which the doctor found three polyps, telling him screening and surveillance are crucial for prevention.

According to the Canadian Cancer Society, colorectal cancer is the second leading cause of death from cancer in men and the third leading cause of death from cancer in women.

"On average, 26 Canadians will die from colorectal cancer every day," the organization's website says.

The society also says 90 per cent of deaths are preventable if caught early.

More information about screening in Canada can be found online.