Surgeon Simply Explains Colon Cancer Surgery

Surgical oncologist explains the diagnosis of and treatment of colon cancer. Anatomy, colonoscopy, and surgery are explained.


The colon is in the sac of the abdomen that contains the abdominal organs whereas the rectum is surrounded by the fat and muscles of the pelvis before it becomes the anal canal and anal opening. The rectum is usually about 12-15 cm long and varies based on body size. When you get a colonoscopy it is easy to tell the distance from the anal opening for the first 20 cm or so but after that locating where you are in the colon is tricky. We can tell somewhat where we are from inside of the colon at the turns of the splenic flexure and hepatic flexure but we don’t really know where we are again until we see this 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 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 tissues of the pelvis and leaves the abdominal sac space. Anything above this point, colon in the abdominal sac is treated like colon cancer and anything that is surrounded by fat and muscle of the pelvis is treated like rectal cancer. Again, the rectum can be estimated from the inside with a colonoscopy as the last 15 cm or so before you get to the anal opening.
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 colon or rectal cancer it is called adenocarcinoma – this is by far the most common form of colon and rectal cancer. When you start getting colonoscopies at 45 years of age or 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. The goal of colonoscopies 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 ok every 10 years unless the doctor finds a polyp in which case you should do a repeat colonoscopy in 5 years or even sooner perhaps.
Most colon cancers grow in the right side of the colon or the last part of the colon in this C or S shaped 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 the 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 and are part of your immune system. In the colon the lymph nodes tend to filter out cancer cells that get stuck in the lymph node and can grow. We want to know if the cancer cells have spread to the lymph nodes and obviously 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 which 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.