|
Colonic
cancer screening
DISCLAIMER
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 for...to "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.
***give me your comments about this
page***
check out the Highest
TRUTH
(posted 5 July 1999 (1st update, 18 June 2000;
then, 8 June 2002; latest addition 31 July 2012)
|