The Truth... What is it?

Colonic cancer screening


6% of Americans will get colon cancer with over 130,000 new cases each year, there being around 50,000 colon cancer deaths per year. 90% of the new cancers are diagnosed after the age of 50. Physicians tend to advise early detection of colon (large intestine) cancers. For general check-ups, and almost any time a rectal exam is done in a hospital, a test may be done for "blood in the stool". Conventional opinion is that most colonic cancers are preceded by a polyp (a mushroom-shaped outgrowth from the intestinal lining). These outgrowths often become irritated and bleed in small amounts. Prior to becoming a cancer, most polyps will become at least as large as a dime.

Many other things cause blood to be in the stool; so, most of the time, a positive test for blood in the stool is a "false positive" test for cancer. On the other hand, a major percentage of polyps and cancers don't cause a positive blood test even though they are present (a false negative test). We have great confidence in the processes set up by the radiologists and gastroenterologists working closely (through all or parts of) with Lexington Medical Center: check them out for your choice of doctors for these tests and an appointment.

Hunting the polyps:

At an earlier age if there is any family history of colonic cancer, or at about age 50, it is considered "better" to actually look "screen" for...polyps and cancers. Looking is done by X-ray exams or by "lights" or cameras/viewers on a flexible rod or tube.

The hated "bowel prep":

By any method, the patient goes through an objectionable overnight purging of the bowel in hopes of cleaning out all feces so that the methods will allow one to be able to "see". Of the x-ray studies, air-contrast barium enema (BE) is the most sensitive, though virtual colonoscopy (VC) by CT exam has matching promise (not fulfilled as of mid-2012). Of the "lights" (endoscopy), total colonoscopy (it uses a "light" long enough to pass through the entire 3 to 4 feet of large bowel) is the most sensitive. It also is the only total-colon screening method which does not require blowing up the entire bowel with air (like a balloon), holding that air in during the exam, and then having the patient release (as a possibly-embarrassing huge poot, fart, or flatus) the air...possibly loudly in the presence of the technologist or others. Colonoscopy is better than BE or VC (except when the gastroenterologist determines that it is inadvisable).

Polyp biopsy or removal:

If anything is seen which might be cancer or a polyp, it is usually biopsied (possibly not immediately biopsied if the patient's blood has been "thinned" by medicines to reduce blood clotting). A biopsy is a small piece of tissue which is then sent for a pathologist's examination under a microscope. If the biopsy is actually from a cancer, it is the pathologist who is able and responsible to make that decision. If it is not a cancer, then the pathologist's job is to determine what type of polyp it is. You see, of the 6 or more types of polyps, only two types tend to precede the development of cancer, both by an "adenomatous" route. Those two types of polyp are usually evident by the routine microscopic exam. But, sometimes a special proliferation-marker stain is needed (such as Ki67) to make sure that a polyp is, or is not, wholly or partially (serrate or mixed adenoma) adenomatous. When the pathologist diagnoses that type (one of several varieties of adenomatous/adenoma polyp) of polyp, then the patient must be re-examined at more frequent intervals than with any of the other types. The object of the pathologist is to be SURE and find either cancerous or adenomatous change in the biopsies, no matter how subtle they might be.

Since a person can have one or many growths at the time of colonoscopy, the examining doctor may try to keep each sample accurately identified as to its precise location in the large bowel. And, the pathologist must do his/her work in such a way that all of this identifying information is kept straight in the pathology report back to your doctor. Should only one of several biopsied areas contain cancer, we need to be sure of the correct location so that a surgeon will remove the correct portion of large intestine and potentially save the patient's life.

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(posted 5 July 1999 (1st update, 18 June 2000; then, 8 June 2002; latest addition 31 July 2012)