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About bowel cancer

Find out about who gets bowel cancer, where it starts and how common it is.

Bowel cancer means cancer that starts in the colon (large bowel) or back passage (rectum). It is also known as colorectal cancer.
 

Who gets it

Both men and women can get bowel cancer. Most people are aged 50 or over when they are diagnosed.

The risk of developing bowel cancer depends on many factors, including:

  • age
  • genetics and family history
  • medical conditions such as familial adenomatous polyposis (FAP), Lynch syndrome, ulcerative colitis and Crohn’s disease
  • diet and lifestyle factors
  • radiation

Colon 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
Diagram showing the parts of the large bowel

Rectal cancer

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.

How bowel cancer grows

The bowel walls are made up of several layers of body tissues. Bowel cancers start in the innermost layer – the lining.

Most begin as a small growth called a polyp or adenoma. If left untreated, they might become cancerous and grow into the muscle layers under the lining of the bowel and then through the bowel wall.

The cancer can then spread into organs that are close to the bowel, such as the bladder, womb or prostate gland.

Doctors think most bowel cancers take 5 to 10 years or more to develop.

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.

Diagram showing the most common sites for bowel cancer to spread to

How common it is

Around 41,000 people are diagnosed with bowel cancer in the UK each year. It is the 4th most common cancer in the UK.

 

Last reviewed: 
15 Aug 2015
  • Cancer Statistics in the UK
    Cancer Research UK

  • Essential Clinical Anatomy (5th edition)
    KL Moore, AMR Agur and AF Dalley
    Wolters Kluwer, 2015

  • Principles and practice of oncology (10th edition)
    VT De Vita, S Hellman and SA Rosenberg
    Lippincott, Williams and Wilkins, 2015

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