Why do I say this? Well, flexible sigmoidoscopy at its best only evaluates the distal (last) third of the your colon, the descending portion from about the splenic flexure onwards. It ignores the proximal ascending colon as well as the transverse colon in that it doesn't have the same reach. Furthermore, the prep for the procedure is nothing at all like the arduous bowel cleansing required for colonoscopy. So if your bowel isn't cleaned out from the top down but rather just a simple enema, and we only look at a portion of the colon, the procedure can't be good enough, right? Conventional wisdom compares flexible sigmoidoscopy to performing mammograms on just one breast when the patient has two.
What's the take message? Something is better than nothing, just like a bird in the hand is worth two in the bush. Sure, colonoscopy preceded by complete bowel prep & cleansing is theoretically better in many different aspects than flexible sigmoidoscopy preceded by an enema. But if patients are not willing to undergo the more involved procedure, what good is it for the general population? Don't forget that checking stool for blood is actually a bit late since you're hoping that the colon cancer announces its presence by bleeding whereas the two invasive procedures actively search for benign polyps to remove prior to morphing into adenomas and then adenocarcinomas. The difference between the two is how much territory is analyzed. But as of this week, it appears for now that the flexible sigmoidoscopy is good enough in the battle against colon cancer. As for mammograms, I'm still going to recommend screening both breasts until a peer-reviewed article demonstrates otherwise.