Bowel cancer

Bowel cancer is a general term for cancer that begins in the large bowel. Depending on where in the bowel the cancer starts, bowel cancer is sometimes called colon cancer or rectal cancer.

Symptoms of bowel cancer include blood in your stools (faeces), an unexplained change in your bowel habits, such as prolonged diarrhoea or constipation, and unexplained weight loss.

Cancer can sometimes start in the small bowel (small intestine), but small bowel cancer is much rarer than large bowel cancer.

The large bowel

The bowel is part of the digestive system. It has two main purposes:

  • to absorb energy, water and nutrients from the food you eat
  • to pass out the remaining waste products from your body in the form of stools

The large bowel is made up of five sections:

  • The ascending colon runs from the end of the small intestine and up the right-hand side of the abdomen.
  • The transverse colon runs under the stomach and across the body from right to left.
  • The descending colon runs down the left-hand side of the abdomen.
  • The sigmoid colon is an S-shaped bend that connects the descending colon to the rectum. 
  • The rectum is the final section of the bowel. It is a small pouch that is connected to the outside opening of the bowel (the anus), through which stools are passed.

How common is bowel cancer?

In Ireland , bowel cancer is the third most common type of cancer. An estimated 2,270 new cases are diagnosed each year.

Between 2007-2009, on average each year 943 cases of bowel cancer were diagnosed in women, making it the third most common cancer in women after non-melanoma skin cancer breast cancer. There were on average each year 1,327 cases in men, making it the third most common cancer after non-melanoma skin cancer and prostate lung cancer.

Approximately 80% of bowel cancer cases develop in people who are 60 or over. Two-thirds of bowel cancers develop in the colon, with the remaining third developing in the rectum.

In Ireland, an estimated 910 people die from bowel cancer each year.

Factors that increase your risk of getting bowel cancer include:

  • Age: around 80% of people diagnosed with bowel cancer are over 60.
  • Diet: a diet high in fibre and low in saturated fat could reduce your bowel cancer risk. A diet high in red or processed meats can increase your risk.
  • Healthy weight: leaner people are less likely to develop bowel cancer than obese people.
  • Exercise: being inactive increases the risk of getting bowel cancer.
  • Alcohol and smoking: high alcohol intake and smoking may increase your chances of getting bowel cancer.
  • Family history and inherited conditions: having a close relative with bowel cancer puts you at much greater risk of developing the disease.
  • Related conditions: having certain bowel conditions can put you more at risk of getting bowel cancer.


Surgery is the mainstay of treatment.for bowel cancer.Sometimes, it is helpful to use other treatments in addition, to get the best outcome . As with most types of cancer, the outlook for an individual depends largely on how far the cancer has advanced by the time it is diagnosed.

If bowel cancer is diagnosed in its earliest stages, the chances of surviving for a further five years is 90%, and a complete cure is usually possible. However, bowel cancer that is diagnosed in its most advanced stage only has a five-year survival rate of 6% and a complete cure is unlikely.

Screening can diagnose cancer at its earliest stage and can increase the chance of successful treatment.


Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
A disease is an illness or condition that interferes with normal body functions.
Stool (also known as faeces) is the solid waste matter that is passed from the body as a bowel movement.
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Early bowel cancer may have no symptoms. Some symptoms of later bowel cancer can also occur in people with less serious medical problems, such as haemorrhoids (piles). See your doctor if you notice any of the symptoms below.

The initial symptoms of bowel cancer include:

  • blood in your stools (faeces) or bleeding from your rectum
  • a change to your normal bowel habits that persists for more than six weeks, such as diarrhoea, constipation or passing stools more frequently than usual
  • abdominal pain
  • unexplained weight loss

As bowel cancer progresses, it can sometimes cause bleeding inside the bowel. Eventually, this can lead to your body not having enough red blood cells. This is known as anaemia.

Symptoms of anaemia include:

  • fatigue
  • breathlessness

In some cases, bowel cancer can cause an obstruction in the bowel. Symptoms of a bowel obstruction include:

  • abdominal pain
  • constipation
  • vomiting

When to seek medical advice

See your GP if you have any of the symptoms above. While the symptoms are unlikely to be the result of bowel cancer, these types of symptoms always need to be investigated further.

National Colorectal Screening Programme

The National Cancer Screening Service is currently developing Ireland’s first national colorectal screening programme, for men and women aged 55-74. The programme is scheduled for introduction later in 2012, initially targeting men and women aged 60-69.


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How does cancer begin?

Cancer occurs when the cells in a certain area of your body divide and multiply too rapidly. This produces a lump of tissue known as a tumour.

Most cases of bowel cancer first develop inside clumps of cells on the inner lining of the bowel. These clumps are known as polyps. However, if you develop polyps, it does not necessarily mean that you will get bowel cancer.

Exactly what causes cancer to develop inside the bowel is still unknown. However, research has shown that several factors may make you more likely to develop it. You cannot do anything about some of these factors, but others you can change.

Family history

There is evidence that bowel cancer can run in families. Around 20% of people who develop bowel cancer have a close relative (mother, father, brother or sister) or a second-degree relative (grandparent, uncle or aunt) who have also had bowel cancer.

It is estimated that if you have one close relative with a history of bowel cancer, your risk of getting bowel cancer is doubled. If you have two close relatives with a history of bowel cancer, your risk increases four-fold.


A large body of evidence suggests that a diet high in red and processed meat can increase your risk of developing bowel cancer. For this reason, the Department of Health advises people who eat more than 90 grams (cooked weight) of red and processed meat a day to cut down to 70 grams.

There is also good evidence that a diet high in fibre and low in saturated fat could help reduce your bowel cancer risk. Cancer experts think this is because this type of diet encourages regular bowel movements.


People who smoke cigarettes are 25% more likely to develop bowel cancer, other types of cancer and heart disease than people who do not smoke.


A major study, called the EPIC study, showed that alcohol was associated with bowel cancer risk. Even small amounts of alcohol can put you at higher risk of getting bowel cancer. The EPIC study found that for every two standard drinks of alcohol a person drinks each day, their risk of bowel cancer goes up by 8%.


Obesity is linked to an increased risk of bowel cancer. Obese men are 50% more likely to develop bowel cancer than people with a healthy weight. Morbidly obese men, who have a body mass index (BMI) of over 40, are twice as likely to develop bowel cancer.

Obese women have a very small increased risk of developing the condition, and morbidly obese women are 50% more likely to develop bowel cancer than women with a healthy weight.


People who are physically inactive have a higher risk of developing bowel cancer. You can help reduce your risk of bowel and other cancers by being physically active every day. Your risk could be cut by up to one-fifth if you do an hour of vigorous exercise every day or two hours of moderate exercise (such as vacuum cleaning or brisk walking).

Digestive disorders

Some conditions may put you at a higher risk of developing bowel cancer. People with Crohn's disease are 2-3 times more likely to develop bowel cancer. The risk of developing bowel cancer is much higher in people with ulcerative colitis, and as many as 1 in 20 of these people will go on to develop it.

Genetic conditions

There are two rare inherited conditions that can cause bowel cancer. They are:

  • familial adenomatous polyposis (FAP)
  • hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome

FAP affects 1 in 10,000 people. The condition triggers the growth of non-cancerous polyps inside the bowel. Although the polyps are non-cancerous, there is a very high risk that, over time, at least one will turn cancerous. Almost all people with FAP will have bowel cancer by the time they are 50 years of age.

People with FAP have such a high risk of getting bowel cancer, they are often advised by their doctor to have their large bowel removed by surgery before they reach the age of 25.

HNPCC is a type of bowel cancer caused by a mutated gene. An estimated 2-5% of all cases of bowel cancer are due to HNPCC. Around 90% of men and 70% of women with the HNPCC mutation will develop bowel cancer by the time they are 70 years of age.

As with FAP, removing the bowel as a precautionary measure is usually recommended in people with HNPCC.

Previous Bowel Cancer

Patients who have already had one cancer of the bowel are at a higher risk than average of developing a second bowel cancer. For this reason, most patients who have had cancer already enter a survivorship programme that includes surveillance colonoscopy.


Your GP will begin the diagnosis by asking you about your symptoms and whether you have a family history of bowel cancer.

They will then carry out a physical examination known as a digital rectal examination (DRE). A DRE involves your GP gently placing their finger into your anus, and then up into your rectum.

A DRE is a useful way of checking whether there is a noticeable lump inside your rectum.Approximately 60% of cases of rectal cancer can be palpated on digital rectal examination when the doctor is experienced. It is uncommon for tumours of the upper third of the rectum to be palpable rectally.

A DRE is not painful, but some people may find it a little embarrassing.

If your symptoms suggest that you may have bowel cancer, or the diagnosis is uncertain, your GP will usuaaly have a test for faecal occult blood(blood in the bowel motions) done ,before referring you to hospital for further examination. 

Further examination

Two tests are commonly used to confirm a diagnosis of bowel cancer:

  • A sigmoidoscopy is an examination of your rectum and some of your large bowel.
  • A colonoscopy is an examination of all of your large bowel.

Sometimes patients are given an enema to ensure that the lower part of the bowel is clear of all bowel contents. This will increase the success rate of the test.


A sigmoidoscopy uses a device called a sigmoidoscope, which is a thin tube attached to a small camera and light.

The sigmoidoscope is inserted into your rectum and then up into your bowel. The camera relays images to a monitor. This allows the doctor to check for any abnormal areas within the rectum or bowel that could be the result of cancer.

A sigmoidoscopy can also be used to remove small samples of suspected cancerous tissue so they can be tested in the lab. This is known as a biopsy.

A sigmoidoscopy is not usually painful, but it can feel slightly uncomfortable. Most people can go home after the examination has been completed.


A colonoscopy is similar to a sigmoidoscopy except a larger tube, called a colonoscope, is used to examine your entire bowel.

Your bowel needs to be empty when a colonoscopy is performed, so you will be given a special diet to eat for a few days before the examination and a laxative (medication to help empty your bowel) on the morning of the examination.

You will be given a sedative to help you relax, after which the doctor will insert the colonoscope into your rectum and move it along the length of your large bowel. As with a sigmoidoscope, the colonoscope can be used to obtain a biopsy, as well as relaying images of any abnormal areas.

You should follow all instructions given by your health care team so that your colonoscopy is as successful as possible. You should phone the endoscopy unit if you have any queries about how best to prepare for the test.

A colonoscopy usually takes about one hour to complete, and most people can go home once they have recovered from the effects of the sedative. After the procedure, you will probably feel a bit drowsy for a while, so arrange for someone to accompany you home.

Further testing

If a diagnosis of bowel cancer is confirmed, further testing is usually carried out for two reasons:

  • to check if the cancer has spread from the bowel to other parts of the body
  • to help decide what will be the most effective treatment for you

Tests may be inconvenient and sometimes uncomfortable for you, but the more information your treating team has in advance of planning treatment,the better they can choose the appropriate treatment for the individual stage of the disease.

These tests can include:

  • staging and grading of the cancer
  • computerised tomography (CT) scan
  • ultrasound scans, which can be used to look inside other organs, such as your liver, to see if the cancer has spread there
  • chest X-rays, which can be used to assess the state of your heart and lungs
  • blood tests to detect a special protein, known as a tumour marker, which is released by the cancerous cells in some cases of bowel cancer. 


A biopsy is a test that involves taking a small sample of tissue from the body so it can be examined.
Blood test
During a blood test, a sample of blood is taken from a vein using a needle, so it can be examined in a laboratory.
Stool (also known as faeces) is the solid waste matter that is passed from the body as a bowel movement.
Ultrasound scans are a way of producing pictures of inside the body using sound waves.
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.
An X-ray is a painless way of producing pictures of inside the body using radiation.

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Surgery - colon cancer

If the cancer is at a very early stage, it may be possible to remove just a small piece of the lining of the colon wall. This is known as local excision.

If the cancer has begun to spread into the muscles surrounding the colon, it will usually be necessary to remove an entire section of your colon. Removing some of the colon is known as a colectomy.

Depending on the location of the cancer, possible surgical procedures include:

  • left-hemi colectomy, where the left half of your colon is removed
  • transverse colectomy, where the middle section of your colon is removed
  • right-hemi colectomy, where the right half of your colon is removed
  • sigmoid colectomy, where the lower section of your colon is removed

A colectomy is performed

  • In an open colectomy, the surgeon makes a large incision in your abdomen and removes a section of your colon.
  • as a laparoscopic colectomy,a type of keyhole surgery.

Both techniques are thought to be equally effective in removing cancer and have similar risks of complications. Laparoscopic colectomies have the advantage of a faster recovery time and less post-operative pain.

During surgery, nearby lymph nodes may also be removed. It is usual to join the ends of the bowel together after bowel cancer surgery, but very occasionally this is not possible and a stoma is needed. 

Enhanced recovery programmes

Enhanced recovery surgical programmes may be available for colon, rectal and bowel cancer patients. These programmes differ from traditional surgery by:

  • ensuring patients are in the best possible physical condition before surgery
  • minimising the trauma patients go through during surgery - for example, minimally invasive surgery when possible and better pain control
  • ensuring patients experience the best possible rehabilitation after surgery


Stoma surgery

Sometimes the bowel is re- attached at the time of the first operation, but a stoma is put in place to reduce the risk of complications if the re-attachment does not heal well. In other cases the surgeon may decide that the colon needs to heal

In this case, it will be necessary to find a way of removing waste materials from your body without stools passing through your anus. This is done using stoma surgery.

Stoma surgery involves the surgeon making a small hole in your abdomen, which is known as a stoma. There are two ways that stoma surgery can be carried out.

  • An ileostomy is where a stoma is made in the right-hand side of your abdomen. Your small intestine is separated from your colon and connected to the stoma, and the rest of the colon is sealed. You will need to wear a pouch that is connected to the stoma to collect waste material.
  • A colostomy is where a stoma is made in your lower abdomen and a section of the colon is removed and connected to the stoma. As with an ileostomy, you will need to wear a pouch to collect waste material.

In most cases, the stoma will be temporary and can be removed once your colon has recovered from the effects of the surgery. This will usually take at least nine weeks. Specialist stoma nurses are available to advise you on the best site for a stoma, and about the best sort of pouch to cover the stoma and collect the waste material.

Before you have a colectomy, your care team will be able to tell you whether they think stoma surgery will be necessary and the likelihood that you will need to have a temporary or permanent ileostomy or colostomy.


Surgery - rectal cancer

Two common surgical procedures can be used to treat rectal cancers:

  • anterior rescetion
  • abdominoperineal resection

Anterior resection

Anterior resection is a procedure that is used to treat cases where the cancer is in the upper section of your rectum. The surgeon will make an incision in your abdomen and remove the upper section of your rectum, as well as some surrounding tissue to make sure that any lymph glands containing cancer cells are also removed. They will then attach your colon to the lowest part of your rectum or upper part of the anal canal. Sometimes, they turn the end of the colon into an internal pouch to replace the rectum. You will probably require a temporary stoma to give the join-up time to heal.

Abdominal perineal resection

Abdominoperineal resection is used to treat cases where the cancer is in the lowest section of your rectum. In this case, it will be necessary to remove a large section of your rectum and surrounding muscles to reduce the risk of the cancer regrowing in the same area. This involves removing the anus and its sphincter muscles too, so there is no option except to have a permanent stoma after the operation. Bowel cancer surgeons always do their best to avoid giving people permanent stomas wherever possible.

Trans Anal Surgery

Transanal surgery may benefit a small number of patients who have very early rectal cancer

Side effects of surgery

Bowel cancer operations carry the same risks as other major operations, including the risks of bleeding, infection, developing blood clots or heart or breathing problems. 

One risk is that the join-up in the bowel may not heal properly and may leak inside your abdomen. This is usually only a risk in the first few days after the operation. 

Another risk is for patients having rectal cancer surgery. The nerves controlling passing urine and sexual function are very close to the rectum, and sometimes an operation to remove a rectal cancer can damage these nerves. I

If you are experiencing bowel symptoms after an operation for bowel cancer, you should seek athe advice of your bowel surgeon, who will be able to help you manage your symptom


There are two main ways that radiotherapy can be used to treat bowel cancer. It can be:

  • given before surgery, in some cases of rectal cancer
  • used to control symptoms and slow the spread of cancer, in cases of advanced bowel cancer (called palliative radiotherapy)

Radiotherapy given before surgery for rectal cancer can be performed in two ways:

  • external radiotherapy, where a machine is used to beam high-energy waves at your rectum to kill cancerous cells
  • internal radiotherapy (also known as brachytherapy), where a radioactive tube is inserted into your anus and placed next to the tumour to shrink it

External radiotherapy is usually given daily, five days a week, with a break at the weekend. Depending on the size of your tumour, you may need one to five weeks of treatment. Each session of radiotherapy is short and will only last for 10-15 minutes.

Internal radiotherapy can usually be performed in one session before surgery is carried out a few weeks later.

Palliative radiotherapy is usually given in short, daily sessions, with a course ranging from 2-3 days to 10 days.

Short-term side effects of radiotherapy include:

  • nausea
  • fatigue
  • diarrhoea
  • burning and irritation of the skin around the rectum and pelvis (this looks and feels like sunburn)
  • a frequent need to urinate
  • a burning sensation when passing urine

These side effects should pass once the course of radiotherapy has finished. Tell your care team if the side effects of treatment become particularly troublesome. Additional treatments are often available to help you cope better with the side effects.

Long-term side effects of radiotherapy include:

  • a more frequent need to pass urine or stools
  • blood in your urine and stools
  • infertility
  • impotence in men

If you want to have children, it may be possible to store a sample of your sperm or eggs before treatment begins so that they can be used in fertility treatments in the future.



There are three ways that chemotherapy can be used to treat bowel cancer. It can be:

  • given before surgery for some cases of rectal cancer in combination with radiotherapy
  • given after surgery to prevent the return of cancer
  • given to slow the spread of advanced bowel cancer and to help control symptoms (palliative chemotherapy)

Chemotherapy for bowel cancer usually involves taking a combination of medications that kill cancer cells. They can be given as a tablet (oral chemotherapy), through a drip in your arm or chest (intravenous chemotherapy), or as a combination of both.

Depending on the stage and grade of your cancer, a single session of intravenous chemotherapy can last from several hours to several days.

Most people have regular daily sessions of chemotherapy over the course of one or two weeks before having a break from treatment for another week.

A course of chemotherapy can last up to six months depending on how well you respond to the treatment.

Side effects of chemotherapy include:

  • fatigue
  • nausea
  • vomiting
  • diarrhoea
  • mouth ulcers
  • hair loss
  • redness and soreness on the palms of your hands and the soles of your feet
  • a sensation of numbness, tingling or burning in your hands, feet and neck

These side effects should gradually pass once your treatment has finished. It usually takes three to six months for your hair to grow back.

Chemotherapy can also weaken your immune system, making you more vulnerable to infection. Inform your care team or GP as soon as possible if you experience possible signs of an infection, including:

  • a high temperature (fever) of 38C (100.4F) or above
  • a sudden feeling of being generally unwell

The medications that are used in chemotherapy can cause temporary damage to men's sperm and women's eggs. This means that for women who become pregnant or for men who father a child, there is a risk to the unborn baby's health. Therefore, it is recommended that you use a reliable method of contraception while having chemotherapy treatment and for a further year after your treatment has finished.


Biological treatments

Biological treatments, including cetuximab, bevacizumab and panitumumab, are a newer type of medication known as monoclonal antibodies. Monoclonal antibodies are antibodies that have been genetically engineered in a laboratory. They target special proteins that are found on the surface of cancer cells, known as epidermal growth factor receptors (EGFR). As EGFRs help the cancer to grow, by targeting these proteins, biological treatments can help prevent the cancer spreading.

Biological treatments are usually used in combination with chemotherapy and radiotherapy.

These treatments are not available to everyone with bowel cancer. The National Institute for Health and Clinical Excellence (NICE) in the UK has determined that specific criteria need to be met before they can be prescribed.

There are several ways to reduce your risk of developing bowel cancer.


Research suggests that a low-fat, high-fibre diet that includes plenty of fresh fruit and vegetables (at least five portions a day) and wholegrains can help reduce your risk of getting bowel cancer. It can also reduce your risk of other types of cancer and heart disease.

It is recommended that you do not eat a lot of processed meat and red meat. The Department of Health advises people who eat more than 90 grams (cooked weight) of red and processed meat a day to cut down to 70 grams.


There is a strong body of evidence to suggest that regular exercise can lower the risk of developing bowel cancer, as well as other types of cancer.

It is recommended that adults should do at least 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity (i.e. cycling or fast walking) every week..

Healthy weight

Try to maintain a healthy weight. Changes to your diet and an increase in your physical activities will help to keep your weight under control.


If you smoke, giving up will reduce your risk of developing bowel cancer, as well as many other types of cancer.

The QUITLINE can offer advice and encouragement to help you quit smoking. Call 1850 201 203 or visit the

Your GP or pharmacist can also give you help, support and advice if you want to give up smoking.

Talk to others

Your GP or nurse may be able to reassure you if you have questions, or you may find it helpful to talk to a trained counsellor, psychologist or specialist telephone helpline operator. Your GP surgery will have information on these. Some people find it helpful to talk to other people with bowel cancer at a local support group or through an internet chat room.


Emotional effects

Having cancer can cause a range of emotions. These may include shock, anxiety, relief, sadness and depression. Different people deal with serious problems in different ways. It is hard to predict how knowing you have cancer will affect you. However, you and your loved ones may find it helpful to know about the feelings that people diagnosed with cancer have reported.


Recovering from colon or rectal surgery

Surgeons and anaesthetists have found that using an "enhanced recovery programme" after bowel cancer surgery helps patients recover more quickly.

Many hospitals now use this programme. It involves giving you more information before the operation about what to expect, avoiding giving you strong laxatives to clean the bowel before surgery, and in some cases giving you a sugary drink two hours before the operation to give you energy. 

During and after the operation, the anaesthetist controls the amount of IV fluid you need very carefully, and after the operation you will be given painkillers that allow you to get up and out of bed by the next day.

Most people will be able to start to eat a light diet the day after their operation.

To reduce the risk of deep vein thrombosis (blood clots in the legs), you may be given special compression stockings that help prevent blood clots, or a regular injection with heparin until you are fully mobile.

A nurse or physiotherapist will help you get out of bed and regain your strength so you can go home again within a few days.

With the enhanced recovery programme, most people are well enough to go home within five to six days of their operation. The timing depends on when you and the doctors and nurses looking after you agree that you are well enough to go home.


Coping with a colostomy

If you need a colostomy, you may feel worried about how you look and how others will react to you. Information and advice about living with a stoma - including stoma care, stoma products and 'stoma-friendly' diets - is available via the ileostomy and colostomy topics. If you have a colostomy you should see your bowel cancer surgeon for follow up to discuss specific problems you may be having with the stoma. Specially trained nurses work with bowel cancer surgeons to help patients manage their stoma


Diet after bowel surgery

If you have had part of your colon removed, it is likely that your stools (faeces) will be looser because one of the functions of the colon is to absorb water from the stools. This may mean that you experience repeated episodes of diarrhoea.

You should inform your care team if diarrhoea becomes particularly troublesome because medication is available to help control symptoms.

You may find that some foods upset your bowels, particularly during the first few months after your operation.

Different foods can upset different people, but food and drink that is commonly known to cause problems include:

  • rich and fatty food,
  • fruit and vegetables that are high in fibre, such as beans, cabbages, apples and bananas, and 
  • fizzy drinks, such as cola and beer.

You may find it useful to keep a food diary to record the effects of different foods on your bowel.

If you find that you are having continual problems with your bowels as a result of your diet, and/or you are finding it difficult to maintain a healthy diet, you should contact your care team. You may need to be referred to a dietitian for further advice.


Sex and bowel cancer

Having cancer and its treatment may affect how you feel about relationships and sex. Although most people are able to enjoy a normal sex life after bowel cancer treatment, if you have had a colostomy you may feel self-conscious or uncomfortable.

Talking about how you feel with your partner may help you both to support each other. Or you may feel that you'd like to talk to someone else about your feelings, your doctor or nurse will be able to help.



Content provided by NHS Choices and adapted for Ireland by the Health A-Z.

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