Hi guys Dr. Steen here let's talk about cancer of the colon and rectum first of
all let's talk about anatomy the intestinal tract is as follows food
travels from your mouth through the esophagus into the stomach then into the
small intestine which loops around and eventually empties into the colon and
the right lower abdomen the valve between the small bowel and the colon is
called ileocecal valve the very first portion of the colon next to the
ileocecal valve is called the cecum and the appendix is a long hollow
outpouching from the cecum the colon then runs up the right side of the
abdomen and is generally called the right colon
it turns at the liver it runs across the abdomen to the left side generally
called the transverse colon down the left side generally called the
descending colon it loops in a c or an S shape called the sigmoid colon and then
down through the pelvic soft tissue as the rectum and out as the anus the
turn-up near the liver is called a hepatic flexure since it is near the
liver and the turn in the left upper abdomen is called the splenic flexure
since it is near the spleen the colon is in the sack of the abdomen that contains
the abdominal organs whereas the rectum is surrounded by the fat and muscle of
the pelvis
the rectum is usually about 12 to 15 centimeters long and it varies based on
body size for surgical purposes we essentially break the rectum down into
an upper rectum which is 10 to 15 centimeters from the anus measuring up
from below the middle rectum which is 5 to 10 centimeters from the anal opening
and the lower rectum which is the lowest area of rectum just above the anus again
this varies from person to person when you get a colonoscopy it is easy to tell
the distance from the anal opening for the first 20 centimeters or so but after
that locating where you are in the colon is tricky we can tell somewhat where we
are from inside the colon at the turns of the splenic flexure and the hepatic
flexure but we don't really know where we are again until we see the junction
between the small intestine and the colon again called the ileocecal valve
so we know with good accuracy if we see a colon cancer within a foot or so of
the ileocecal valve and within a foot or so from the anal opening but the rest of
the colon is more of an estimate when we are looking at it just from a
colonoscopy this is why most of the time when we find a colon cancer or rectal
cancer we inject ink into the wall of the colon to mark it permanently with a
tattoo so we can see where the cancer is located from the outside of the colon
when we do surgery colon cancer refers to cancer that occurs from the ileocecal
valve and anywhere through the colon down to the rectum for a surgeon the
major treatment differences between colon cancer and rectal cancer are
differentiated by the point at which the rectum goes into the soft tissue of the
pelvis and leaves the abdominal space sac anything above this point colon in
the abdominal sack is treated like colon cancer and anything that is surrounded
by the fat and muscle of the pelvis is treated like rectal cancer
I am commonly asked what causes colon cancer in general we think that most
colon cancers grow from precancerous mushroom like growths on the inside of
the colon called polyps when a polyp turns into a colon or rectal cancer that
is called adenocarcinoma this is by far the most common form of colon and rectal
cancer when you start getting a colonoscopy at 45 years of age or maybe
even earlier the doctor is looking for polyps not every kind of polyp will turn
into a cancer the doctor will be sure to figure out if you have the dangerous
kind or not the goal of a colonoscopy is to find the polyps and remove them
before they can turn into cancer it takes many years for the progression
from polyp to cancer which is why getting a colonoscopy is okay every 10
years unless the doctor finds a polyp in which case you should do a repeat
colonoscopy in five years or even sooner perhaps typically once a colon or rectal
cancer is found on colonoscopy we want to do a CT scan of your chest and
abdomen to be sure it has not spread or metastasized to other organs such as the
liver or the lungs these pictures are done before doing surgery most colon
cancers grow in the right side of the colon or the last part of the colon in
the C or S portion called the sigmoid colon it is less common to get cancer in
the middle part called the transverse colon if we find a cancer in the right
side of the colon or the cecum we remove the entire right side of the colon we
need to remove much more than just a small area of cancer because for all
true colon cancer we want to remove at least a dozen lymph nodes lymph nodes
are all over your body they are part of your immune system and the colon the
lymph nodes tend to filter out cancer cells that get stuck in the lymph node
and these can grow we want to know if the cancer cells have spread to the
lymph nodes and obviously we want to remove the lymph nodes if they have
cancer in them in the colon the lymph nodes are intertwined with the blood
vessels going to the colon so in order to remove enough lymph nodes 12 at least
we have to remove the blood vessels to the entire right colon
this is why the entire right colon is removed for any cancer located anywhere
from the cecum to the transverse colon after the right colon is removed we can
attach the last part of the small intestine back to the transverse colon
cancer in the right colon rarely needs an ostomy bag since we can almost always
reattach the small intestine to the colon cancer in the transverse colon is
a special case this is up to the surgeon how they removed that portion but cancer
in this location is relatively rare cancer in the descending or sigmoid
colon is removed by taking enough colon out to allow for 12 lymph nodes
also because the sigmoid colon naturally snakes around it can be easier to remove
if cancer is in this floppy section and we can remove the 12 lymph nodes and
blood vessels that are intertwined with the lymph nodes just by removing a
sigmoid colon and then pulling the remaining colon together
this would rarely need an ostomy an ostomy is when we cannot safely put the
intestinal tract back together again a colostomy is a portion of the colon that
is brought up to the skin and open so that stool can come out into a bag I
hope this helps this is an overview of colon cancer
rectal cancer is an entirely different topic and is addressed in a different
video don't forget to subscribe below check out my other videos take care