Bowel cancer is cancer that starts in the large bowel (colon) or back passage (rectum). It is also known as colorectal cancer.
Cancer is when abnormal cells start to divide and grow in an uncontrolled way. The cells can grow into surrounding tissues or organs, and may spread to other areas of the body.
There are two main parts to the bowel, the small bowel and the large bowel.
The food we eat ends up in the large bowel where water and some nutrients are absorbed leaving waste. This passes through the bowel before leaving the body.
The most common type of bowel cancer affects the large bowel, which includes the colon and the back passage. Large bowel cancer is also sometimes called colorectal cancer.
Cancer starts when something goes wrong in a cell and it starts growing uncontrollably to form a tumour.
More than 9 out of 10 people who develop bowel cancer in the UK are over the age of 50.
Your risk of developing bowel cancer may be higher if you have a strong family history of bowel cancer, or you have a genetic condition, or you gave a bowel condition such as colitis.
The good news is that more than half of all bowel cancers could be prevented through lifestyle changes.
These include stopping smoking, being physically active - at least 30 minutes exercise five times a week, keeping to a healthy weight, eating smaller and fewer portions of red and processed meat, choosing wholegrain foods and at least five portions of fruit and veg a day, and cutting down on alcohol.
The less you drink the lower the risk. If you do drink, try and stick within the government guidelines, that is no more than 14 units a week.
The UK has a bowel cancer screening programme for older men and women which aims to find cancer early. Those registered with a GP are sent a kit to test for bowel cancer every two years.
You can find out more information about bowel cancer screening on the Cancer Research UK website.
The bowel makes up a part of the digestive system. It’s split into the small and large bowel. The large bowel includes the:
- back passage (rectum)
- bowel opening (anus)
This section is about colon and rectal cancer. We have separate sections about anal cancer and small bowel cancer.
Where does bowel cancer start?
Where your bowel cancer starts will affect the treatment that you might have. For example, the treatment for colon cancer can be different to the treatment for rectal cancer.
The colon is the first part of the large bowel. It is about 5 feet long and has 4 sections. Cancer can develop in any of these.
The parts of the colon are the:
- Ascending colon – runs up the right side of the abdomen. It is connected to the small intestine by a section of bowel called the caecum
- Transverse colon – runs across the body from right to left, under the stomach
- Descending colon – runs down the left side of the abdomen
- Sigmoid colon – an 'S' shaped bend that joins the descending colon to the back passage
Rectal cancer starts in the last part of the large bowel (the back passage). This part of the bowel stores poo (stool) until it is ready to be passed out of the body.
Rectal cancer is also called cancer of the rectum.
Anal cancer starts in your anus which is the opening at the very end of your large bowel. Poo leaves your body through your anus.
Cancer of the small bowel
The small bowel is between the tummy (stomach) and large bowel.
If bowel cancer spreads
Bowel cancer can spread to another part of the body through the lymphatic system. The lymphatic system is made up of lymph nodes, which are part of the body’s immune system. One of the first places bowel cancer spreads is to the lymph nodes in the tummy (abdomen).
Bowel cancer can also spread to other parts of the body through the bloodstream. The liver is a common place for colorectal cancer to spread because blood flows directly from the bowel to the liver. The cancer can also spread into the lung or bone but this is less common.
How common it is
In 2015, around 41,800 people were diagnosed with bowel cancer in the UK. It is the 4th most common cancer in the UK.
Who gets it
Both men and women can get bowel cancer. It is more common in older people.
The risk of developing bowel cancer depends on many factors, including:
- genetics and family history
- medical conditions such as familial adenomatous polyposis (FAP), Lynch syndrome, ulcerative colitis and Crohn’s disease
- diet and lifestyle factors