I’m going to share a medical secret with you. It’s about having a colonoscopy, as I did yesterday.

When my physician first told me I’d have to have one, I was a little nervous, but I’ve reached the age where you’re supposed to get screened for cancer and other problems, so I was resigned to it. Fortunately, they didn’t find anything wrong. Even more fortunately, the whole hospital experience was a breeze.

What nobody told me was how un-breezy the day before was going to be. Remember, this is a procedure that tens of millions of people have had done. Two members of my extended family have had a colonoscopy within the last couple of years, but neither one of them — nor anyone else — ever shared with me the day-before warning. Since I’m sure you can’t count on your friends or family either, I’ll be the one to give you a heads-up.

The problem is that before the gastroenterologist goes exploring around in your colon with a camera on a tube inserted in your rear end, you have to be, um, as empty as possible. To achieve that, I was given two different kinds of laxatives. One came in pill form and was no problem. The other came in a powdered form, the equivalent of industrial-strength Drano.

The instructions from the doctor said that, on the afternoon before the procedure, I was to mix this prescription laxative with 64 ounces of a non-dairy, non-juice liquid and start drinking it every 10-15 minutes starting at 3pm. I checked the bottle to see how much I’d be consuming, and it read 255 grams. Turns out this laxative is also prescribed to people with serious constipation, in which case the dose is 17 grams per day — and I had to have all 255 grams, meaning I was about to swallow two weeks worth of laxative in two hours!

I briefly considered stirring this stuff into a half-gallon of water, but didn’t think I could take that taste. Instead, I added a whole bottle of orange Gatorade — I can’t stand the stuff, but I figured that the orange flavor would mask the taste of the chalk-like powder.

I was wrong.

It took me exactly one glass to realize that this was going to be an experience in nastiness that would go on until I finished it all. And this stuff works quickly. I had only finished the second glass when I began the first of several hurried visits to the bathroom. I’ll leave out the disgusting parts of this, which I’m sure you can imagine, but suffice it to say that it was clear how the rest of my afternoon and evening were going to play out from that point on. I consider it one of the most unpleasant days of my life.

Somewhere around the fifth glass, I considered just giving up. Then I realized that would mean having to start the whole process again some other time, so it just seemed to make sense to get it over with. It also occurred to me that, despite not eating anything all day long, I wasn’t hungry at all. My brain must have recognized that adding anything solid into this human sluice-gate system of mine, where whatever went in would be coming right back out, was not a pleasant prospect.

By the seventh glass, I thought about President Bush — but not in a political cheap shot sense. He had just undergone a colonoscopy 9 days earlier, and the media had duly reported that doctors had removed five polyps from his colon and everything was fine. What they failed to mention was that he must have gone through the same preparations I was in the midst of. That means he’d gone through the same discomfort and was just as frequently out of action. Sounds to me like the 25th Amendment should have been invoked the day before the colonoscopy, too. There’s no way even the President of the United States could have been thinking clearly while drinking down this Gatorade Goo and making frequent visits to the presidential potty.

The next morning, my wife and daughter drove me to the hospital, and here’s where the easy part began. The staff at Barnes West were nice and efficient and had me ready to go within 15 minutes of my arrival. The toughest part was figuring out how to tie a bowtie knot behind my back on that backwards hospital gown (I actually was concerned with making sure that it was completely closed back there, until I remembered that half of the nursing staff was about to get a very good view of my butt, and it was just one of many they’d face that day).

Soon, gastroenterologist Dr. David Goran came in and explained what was going to happen during both my colonoscopy and endoscopy. He joked that they’d be sure to use a different tube when they went down my throat into my stomach than the one that went up the other end into my colon. He asked if I had any questions, and when I didn’t, he said, “Okay, then we’ll see you later.” For a moment, I thought this meant he was leaving. Then I realized they were about to give me the general anesthesia. In the next moment, I was unconscious. In the moment after that, they were waking me up and he was telling me that everything had gone well and I was fine.

Because I wasn’t awake for any of it, I have no memory of anything being done. There’s actually part of me that wonders if anything was done, since I didn’t feel a thing during or after the procedure. It’s like when the mechanic tells you he’s changed the oil on your car — how do you know if he really did? It’s not like Dr. Goran showed me a used air filter he’d replaced. I’m sure there’s medical photographic evidence, but I’m not really interested in seeing it. After all, how would I know it came from inside me? I doubt that I’d recognize my own colon with any degree of certainty.

None of that mattered. I’d been checked out and there were no problems, so after they released me from the recovery room, the next stop was our favorite pizza place. No, I didn’t wash it down with Gatorade. But I did make a mental note to tell everyone I could how easy the actual colonoscopy was and how horrible the day before had been.

Please recognize that I’m not telling you any of this to discourage you from having a colonoscopy, which is a potentially life-saving procedure. I hope you live long enough to have many of these screenings, and that each one shows nothing wrong.

I just want you to know what you’re in for on the day before, since no one warned me.