(This Dave Barry column was originally published Feb. 22, 2008.)

OK. You turned 50. You know you're supposed to get a colonoscopy. But you haven't. Here are your reasons:

1. You've been busy.

2. You don't have a history of cancer in your family.

3. You haven't noticed any problems.

4. You don't want a doctor to stick a tube 17,000 feet up your butt.

Let's examine these reasons one at a time. No, wait, let's not. Because you and I both know that the only real reason is No. 4. This is natural. The idea of having another human, even a medical human, becoming deeply involved in what is technically known as your ''behindular zone'' gives you the creeping willies.

I know this because I am like you, except worse. I yield to nobody in the field of being a pathetic weenie medical coward. I become faint and nauseous during even very minor medical procedures, such as making an appointment by phone. It's much worse when I come into physical contact with the medical profession. More than one doctor's office has a dent in the floor caused by my forehead striking it seconds after I got a shot.

In 1997, when I turned 50, everybody told me I should get a colonoscopy. I agreed that I definitely should, but not right away. By following this policy, I reached age 55 without having had a colonoscopy. Then I did something so pathetic and embarrassing that I am frankly ashamed to tell you about it.

What happened was, a giant 40-foot replica of a human colon came to Miami Beach. Really. It's an educational exhibit called the Colossal Colon, and it was on a nationwide tour to promote awareness of colo-rectal cancer. The idea is, you crawl through the Colossal Colon, and you encounter various educational items in there, such as polyps, cancer and hemorrhoids the size of regulation volleyballs, and you go, ''Whoa, I better find out if I contain any of these things,'' and you get a colonoscopy.

If you are as a professional humor writer, and there is a giant colon within a 200-mile radius, you are legally obligated to go see it. So I went to Miami Beach and crawled through the Colossal Colon. I wrote a column about it, making tasteless colon jokes. But I also urged everyone to get a colonoscopy. I even, when I emerged from the Colossal Colon, signed a pledge stating that I would get one.

But I didn't get one. I was a fraud, a hypocrite, a liar. I was practically a member of Congress.

Five more years passed. I turned 60, and I still hadn't gotten a colonoscopy. Then, a couple of weeks ago, I got an e-mail from my brother Sam, who is 10 years younger than I am, but more mature. The email was addressed to me and my middle brother, Phil. It said:

``Dear Brothers,

``I went in for a routine colonoscopy and got the dreaded diagnosis: cancer. We're told it's early and that there is a good prognosis that they can get it all out, so, fingers crossed, knock on wood, and all that. And of course they told me to tell my siblings to get screened. I imagine you both have.''

Um. Well.

First I called Sam. He was hopeful, but scared. We talked for a while, and when we hung up, I called my friend Andy Sable, a gastroenterologist, to make an appointment for a colonoscopy. A few days later, in his office, Andy showed me a color diagram of the colon, a lengthy organ that appears to go all over the place, at one point passing briefly through Minneapolis. Then Andy explained the colonoscopy procedure to me in a thorough, reassuring and patient manner. I nodded thoughtfully, but I didn't really hear anything he said, because my brain was shrieking, quote, ``HE'S GOING TO STICK A TUBE 17,000 FEET UP YOUR BUTT!''