What is bowel cancer?
Bowel cancer, also known as colorectal cancer, can affect any part of the colon or rectum; it may also be referred to as colon cancer or rectal cancer, depending on where the cancer is located.
The colon and rectum are parts of the large intestine.
The colon is the longest part of the large intestine (the first 1.8 metres). It receives almost completely digested food from the ceacum (a pouch within the abdominal cavity that is considered to be the beginning of the large intestine), absorbs water and nutrients, and passes waste (stool/faeces/poo) to the rectum.
The colon is divided into four parts:
- the ascending colon is the start of the colon. It is on the right side of the abdomen. It continues upward to a bend in the colon called the hepatic flexure.
- the transverse colon follows the ascending colon and hepatic flexure. It lies across the upper part of the abdomen. It ends with a bend in the colon called the splenic flexure.
- the descending colon follows the transverse colon and splenic flexure. It is on the left side of the abdomen.
- the sigmoid colon is the last part of the colon and connects to the rectum.
The proximal colon is the ascending colon and the transverse colon together. The distal colon is the descending colon and the sigmoid colon together.
The rectum is lower part of the large intestine (the last 15 centimetres) that connects to the sigmoid colon. It receives waste (stool/faeces/poo) from the colon and stores it until it passes out of the body through the anus.
The anus is the opening at the lower end of the rectum through which waste is passed from the body.
Cancer in the anal canal or anus is treated differently from and is less common than bowel cancer.
Most bowel cancers start as benign, non-threatening growths – called polyps – on the wall or lining of the bowel.
Polyps are usually harmless; however, adenomatous polyps can become cancerous (malignant) and if left undetected, can develop into a cancerous tumour.
In advanced cases, the cancerous tumour can spread (metastasise) beyond the bowel to other organs.
