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What is bowel cancer?
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Last reviewed January 2013
Contents
The digestive system
What is bowel cancer
Symptoms of bowel cancer
How common is it
What causes bowel cancer
Useful websites
Information reviewed by
The digestive system
The bowel is part of the digestive system which is sometimes called the gastrointestinal (GI) tract. The
digestive system helps the body to digest food and turn it into energy for the body to use. It also gets rid of
remaining solid waste matter (called stools or faeces) from the body. The digestive system starts at the
mouth and ends at the anus.
The bowel has two main parts:
Small bowel – takes food from the stomach and absorbs nutrients. It is about five metres long.
Large bowel – the colon absorbs salts and water and turns the rest into waste (stools or faeces). It has
several sections:
Cecum - a pouch at the beginning of the large bowel that receives waste from the small bowel.
The appendix is a small tube hanging off the end of the cecum.
Colon - the main working area of the large bowel. The colon is divided into four parts
(ascending colon, transverse colon, descending colon and sigmoid colon) and stretches from
the cecum to the rectum. It is about 1.5 metres long.
Rectum - the last 15 to 20 centimetres of the large bowel. The rectum stores waste until it is
passed during a bowel motion.
Anus - the opening at the end of the digestive tract. The anus has strong sphincter muscles that
form a valve. During a bowel motion these muscles relax to release stools from the rectum.
What is bowel cancer?
Bowel cancer is cancer in any part of the colon or rectum. Bowel cancer can develop in two ways: it can grow
from the inner lining of the bowel or from small growths on the bowel wall called polyps. These mushroomshaped growths are usually harmless (benign) but may become cancerous over time.
If untreated bowel cancer can spread (metastasise) deeper into the wall of the bowel. From there it can
spread to the lymph nodes (glands).
Lymph nodes are small, bean-shaped masses that collect and destroy bacteria and viruses in the body.
They are part of the body’s lymphatic system which plays an important role in the functioning of the immune
system.
Later bowel cancer can spread to other organs such as the liver or lungs. In most cases it develops fairly
slowly and may stay in the bowel for months or years before spreading.
In this information the colon and rectum together are known as the large bowel. The word colorectal is
commonly used to describe cancers of the colon or rectum. Bowel cancer is also called colorectal cancer.
The terms large intestine, large bowel and colon all refer to the same organ. The term large intestine is not
used in this information.
Symptoms of bowel cancer
In its early stages bowel cancer often has no noticeable symptoms.
Symptoms some people may experience include:
A change in bowel habits such as the look of stools, constipation or smaller, more frequent bowel
movements.
A feeling of fullness in the bowel or rectum.
A feeling that the bowel hasn’t emptied completely after a bowel movement.
Blood in the stool or on the toilet paper.
Unexplained weight loss.
Weakness or fatigue.
Rectal or anal pain.
Feeling very tired or breathless (anaemia).
Cancer of the bowel may cause a blockage (bowel obstruction). This causes symptoms such as abdominal
pain, feeling bloated, constipation and being sick. Many of the symptoms of bowel cancer are common to
other large bowel conditions such as haemorrhoids or tears in anal tissue. Some foods or medications can
also change bowel habits or cause stools to turn red or black. If you have any of the above symptoms talk to
your doctor.
How common is it?
About one in 17 men and one in 25 women will develop bowel cancer before the age of 75.
What causes bowel cancer?
The exact cause of bowel cancer is not known. However some factors increase the chance of developing
bowel cancer including:
Getting older – bowel cancer more commonly affects people aged 50 and over.
Bowel diseases – people who have an inflammatory bowel disease, such as Crohn’s disease or
ulcerative colitis, have a significantly increased risk.
Lifestyle factors – being overweight, doing little physical activity, a diet high in fat or animal products,
alcohol consumption and smoking can play a part.
Strong family history – bowel cancer can run in the family. Whether you’re at increased risk depends
on who in your family was diagnosed and at what age.
Inheriting a rare genetic disorder
Polyps in the colon are a risk factor for bowel cancer. If polyps are removed the risk of bowel cancer is
reduced.
Useful websites
The internet has many useful resources of information although not all websites are reliable. The websites
listed below are good sources of reliable information.
Australian
Cancer Council SA
www.cancersa.org.au
Cancer Council Australia
www.cancer.org.au
healthdirect
www.healthdirect.gov.au
Commonwealth Department of Health and Ageing
www.health.gov.au
Health SA
www.healthsa.sa.gov.au
National Health and Medical Research Council
www.nhmrc.gov.au
Australian Association of Stomal Therapy Nurses
www.stomaltherapy.com
Ostomy NSW
www.ostomynsw.org.au
Continence Foundation of Australia
www.continence.org.au
National Public Toilet Map
www.toiletmap.gov.au
National Cancer Screening Programs
www.cancerscreening.gov.au
Carers SA
www.carers-sa.asn.au
International
American Cancer Society
www.cancer.org
Macmillan Cancer Support
www.macmillan.org.uk
US National Cancer Institute
www.cancer.gov
Information reviewed by: Karen Barclay, Colorectal Surgeon, The Northern Hospital, Lecturer in Surgery,
University of Melbourne, VIC; Carole Arbuckle, Cancer Nurse, Cancer Council VIC; Karen Bowers, Eat it to
Beat it Strategy Project Officer, Cancer Council NSW; Darrell Bowyer, Consumer; Rebecca Foot-Connolly,
Stomal Therapy Nurse, The Alfred Hospital, VIC; Bernadette Hadfield, Stomal Therapy Nurse, The Alfred
Hospital, VIC; Melissa Heagney, Media and Communications Advisor, Cancer Prevention Unit, Cancer
Council VIC; Dorothy King, Consumer; and Loreto Pinnuck, Stomal Therapist, Wound Consultant, Paediatric
Continence Specialist, Monash Medical Centre, VIC.
Content printed from https://www.cancersa.org.au/information/a-z-index/what-is-bowel-cancer
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