Where is the colon and rectum?
The colon and rectum (or the large intestine) is the last part of the gastrointestinal tract. Broadly our gastrointestinal tract consists of
Oesophagus which connects the mouth to the stomach where the food is stored and released periodically into the small intestine where the food is broken down and absorbed. The food residue enters the colon where water is absorbed and the food residue is converted to waste product by the action of bacteria. The rectum is the terminal part of the colon in which the waste produce (faeces) is stored before being expelled via the anus. |
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What is colorectal cancer?
Our body is made up of basic units called cells. When these cells grow in an uncontrolled manner, a malignant growth or a cancer is formed.
Colorectal cancer is formed from cells which line the inner wall of the colon and rectum. This lining is called the mucosa. At this stage the cancer is termed non-invasive i.e. the cancer cells have not spread out of the colon. If undetected, the cancer will grow bigger and project into the lumen of the colon. It will also invade through the colon wall and spread via several routes:
1. Invasion of neighbouring intestines and organs
2. Lymphatic system into neighbouring lymph glands called mesenteric lymph nodes.
3. Blood stream to the liver where secondary malignant deposits can be formed.
Colorectal cancer that has invaded the lymph nodes or the liver is in the advanced stage.
What are polyps?
Polyps are benign lumps on the inner wall of the colon and rectum. They look like a small grape attached to the colon by a stalk. They are fairly common in people above 50 years old. Some types of polyps (called adenomatous polyps) may transform into cancer. If such polyps are detected, they should be removed to prevent the development of cancer.
Normal Colon |
Colon with Polyp |
Certain features of a polyp make one suspect that it may be malignant:
- Polyp > 1 cm diameter
- Sessile polyps (i.e. polyps without a stalk)
- Multiple polyps
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