Location of the Colon and Rectum - Why it is Important for Colorectal Cancer

In this video, we review colorectal anatomy as well as lymph node anatomy to understand the treatment for colorectal cancer.  

Read the full video transcript below:

It's a lot easier to understand colorectal cancer treatment when you first understand colorectal anatomy. 

The colon is a question mark shaped tube organ that absorbs water and nutrients from food before they leave the body through the anus. It is split up into several parts. 

The ascending colon is on the right side of the body and starts at the junction with the small intestine and goes up to the right upper quadrant of the abdomen near the liver. It then connects with the transverse colon, which goes across from the right side to the left side of the upper abdomen. 

The descending colon docks down the left side of the body. And feeds into the sigmoid colon which enters the pelvis. The rectum is in the true pelvis. And stool ultimately leaves the body through the anus.

There's an important dividing line towards the top of the pelvis, and cancers are treated very differently if they arise from above this dividing line versus below this line. The main difference is in lymph node drainage. Lymph nodes are meant to clear infection, but cancer cells can also get into lymph nodes. 

Lymph nodes above this dividing line in the true colon tend to drain in a somewhat sporadic fashion. Because of this reason, very focused treatments like radiation therapy end up having a very high level of toxicity or side effects and are generally not used for true colon cancer. 

In the true pelvis, lymph node drainage is much more organized and predictable. For this reason, focused treatments like radiation are better tolerated with fewer side effects and have a greater benefit in terms of controlling the cancer. 

This is not medical advice. Talk to your doctor before making a medical decision.