Diagnosing bowel cancer

Sunday 1 February, 2015

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On this page: Screening | General tests | Tests to find cancer | Further tests | Staging bowel cancer | Prognosis | Which health professionals will I see? | Keypoints

Some people have tests for bowel cancer because they have symptoms. Others may not have any symptoms but have a strong family history of bowel cancer or have received a positive result from a screening test (see below).

To diagnose bowel cancer, your general practitioner (GP) will examine you and refer you to a specialist for further tests. The tests you have depend on your specific situation and may include:

  • general tests to check your overall health and body function
  • tests to find cancer
  • tests to see if the cancer has spread (metastasised).

Some tests may be repeated during or after treatment to check how well the treatment is working.

Waiting for the test results can be a stressful time. It may help to talk to a friend or family member or to a health care professional, or you can call Cancer Council 13 11 20.

Screening for bowel cancer

Screening is the process of looking for polyps or cancer in people who don’t have any symptoms. It is particularly important for bowel cancer, which often has no symptoms in its early stages.

The faecal occult blood test (FOBT) looks for microscopic traces of blood in your stools, which may be a sign of polyps, cancer or another bowel condition. An FOBT does not diagnose cancer, but it helps your doctor decide whether to do further tests, such as a colonoscopy (see below).

People over 50 should have an FOBT every two years. Because the test helps catch bowel cancer early, this can significantly improve the chance of surviving the disease.

Through the National Bowel Cancer Screening Program, many people 50 and over are automatically sent free FOBT kits – phone 1800 118 868 or see cancerscreening.gov.au. Kits can also be purchased from some pharmacies. You complete the test at home.

The FOBT is only for low-risk people without symptoms of bowel cancer. Anyone with symptoms of bowel cancer should talk to their doctor about having a colonoscopy or other tests.

If you have a strong family history or a genetic condition linked to bowel cancer, the FOBT is not the right test for you. You and other family members may need screening colonoscopies as a precaution. A screening colonoscopy is recommended for high-risk people at 50 years of age, or 10 years before the earliest age a family member was diagnosed with bowel cancer, whichever comes first. It should be repeated every one to two years. 

General tests

Physical examination

Your doctor will examine your body, feeling your abdomen for any swelling.

To check for problems in the anus and rectum, your doctor will insert a gloved finger into your anus and feel for any lumps or swelling. This is called a digital rectal examination (DRE), and it helps the doctor detect problems in the lowest part of the bowel.

The DRE may be uncomfortable, but it shouldn’t be painful. Because the rectum is a muscle, it can help to try to relax during the examination. It might make you feel like you are going to have a bowel movement, but it is very unlikely that this will happen.

The doctor may also insert a small, rigid telescope into the anus to see the lining of the rectum. You do not need an empty bowel or anaesthetic for this examination. Depending on the type of telescope used, the procedure is called a proctoscopy or rigid sigmoidoscopy. 

Blood test

You may have a blood test to assess your general health and to look for signs that suggest you are losing blood in your stools.

The blood test may measure chemicals that are found or made in your liver, and check your red blood cell count. Low red blood cell levels (anaemia) are common in people with bowel cancer, but may also be caused by other conditions.

Most doctors also measure the levels of carcinoembryonic antigen (CEA), which is a protein produced by some cancer cells. If your blood tests show that you have a high CEA level, your doctor may organise more tests. This is because other factors, such as smoking or pregnancy, may also increase CEA levels.

"I started to have some bleeding when I went to the toilet. There were no other warning signs – it just happened out of the blue, so I went to see my GP." – Andrew

Tests to find cancer

Flexible sigmoidoscopy

This test allows the doctor to see the rectum and lower part of the colon. To have a flexible sigmoidoscopy, you will need to have an empty bowel (see bowel preparation).

Before the test, you may be given a light anaesthetic or sedation. You will lie on your side while a thin, flexible tube with a light and camera at the end, called a sigmoidoscope, is inserted gently into your anus and guided up through to the bowel. The sigmoidoscope blows carbon dioxide or air into the bowel.

This inflates the bowel slightly and allows the doctor to see the bowel wall more clearly. The camera and light at the end of the tube show up any unusual areas. The doctor can also use the sigmoidoscope to remove a piece of tissue for examination. This is called a biopsy.

A sigmoidoscopy takes about 10–20 minutes. Though it may feel uncomfortable, the test should not be painful. You may experience cramping and pressure in your lower abdomen. This will ease as you clear the remaining air by passing wind.


A colonoscopy examines the whole length of the large bowel. This is generally the most accurate test to examine the large bowel for cancer and polyps. It is still possible, however, that small polyps may be missed, especially if they are behind one of the many folds in the bowel or the bowel is not completely clear.

  • Before a colonoscopy, you will have a bowel preparation to clean your bowel. On the day of the procedure, you will probably be given an anaesthetic so you don’t feel any discomfort or pain. This will also make you drowsy and may put you to sleep during the examination.
  • During the procedure, the doctor will insert a flexible tube with a camera on the end, called an endoscope, into your anus and up into your rectum and colon.
  • Carbon dioxide or air will be passed into the colon. Your doctor will look for abnormal tissue (such as polyps), which will be removed for further examination (biopsy).

An occasional side effect of a colonoscopy is temporary flatulence and wind pain, especially if air rather than carbon dioxide is passed into the bowel during the test. More serious but rare complications include damage to the bowel or bleeding. Your doctor will talk to you about the risks. Overall, the test is safe and the benefits far outweigh the risks for most people.

A colonoscopy usually takes about 20–30 minutes. You will need to have someone take you home afterwards, as you may feel drowsy or weak.

Virtual colonoscopy

A virtual colonoscopy uses a CT or MRI scanner (see further tests) to create images of the colon and rectum and display them on a screen instead of putting an endoscope into your bowel.

Your bowel needs to be empty for the virtual colonoscopy, so you will have a bowel preparation. You will probably lie on your back or stomach and a thin tube will be inserted into your rectum to fill your colon with air. This may feel uncomfortable.

After your colon is inflated, you will be moved into the scanner. The scanner will create 3D images of your colon while you hold your breath for short intervals. The procedure takes 10–15 minutes.

Virtual colonoscopies are not used often because they are not as accurate as colonoscopies and they involve exposure to radiation. They are covered by Medicare only in some circumstances when a colonoscopy isn’t feasible. Although the test is less invasive than a colonoscopy and shows your bowel in detail, your doctor may not be able to see small abnormalities and cannot take tissue samples.

Barium enema

Barium is a white contrast liquid that shows up on x-rays, and a barium enema is a type of bowel x-ray procedure. This test has been largely replaced by colonoscopy, but it might be used in particular circumstances.

Before having a barium enema, you will need a bowel preparation to clean out your bowel. During the procedure, you will lie on an x-ray table while a barium-filled tube is inserted into your rectum and releases barium into your colon. The barium will show up any lumps or swellings, and x-rays of your inflated colon will then be taken. If an abnormal area is found in the bowel, you will probably need to have another test such as a colonoscopy.

Bowel preparation

Before some diagnostic tests, you will have to clean out your bowel. This will help the doctor see inside the bowel clearly.

The cleaning process varies for different people and between hospitals, so ask if there are any specific instructions for you. It’s important to follow the instructions so you don’t have to repeat the test.

Having a bowel preparation may involve:

  • an enema – One common way to clear the bowel is using an enema. This is liquid that is inserted directly into the rectum. The enema solution washes out the lower part of the bowel, and is passed into the toilet along with any faeces.
  • laxatives – Another type of bowel preparation is an oral laxative (in tablet or liquid form), which will cause you to have watery diarrhoea.
  • diet changes – For a few days before the diagnostic test, you may be told to avoid high-fibre foods, such as vegetables, fruit, wholegrain pasta, brown rice, bran, cereals, nuts and seeds. Instead, choose lowfibre options, such as white bread, white rice, meat, fish, chicken, cheese, yoghurt, pumpkin and potato.
  • clear fluids – Your doctor might advise you to drink only fluids, such as broth, water, black tea and coffee, and clear fruit juice without pulp for 12–24 hours before the test. This will help to prevent dehydration.

Consider using soft toilet paper, wet wipes or barrier cream so your skin does not become irritated by the cleaning process.

Talk to your doctor if you have any concerns about the bowel preparation process.

Further tests

If any of the tests above show you have bowel cancer, you will have one or more of the following scans to see if the cancer has spread to other parts of your body.

A scan is painless and is usually done as an outpatient. Most people are able to go home as soon as the test is over.

CT scan

A CT (computerised tomography) scan uses x-ray beams and computer technology to create a detailed, cross-sectional picture of the inside of the body.

Before the scan, dye is injected into a vein to make the pictures clearer. This may make you feel hot all over and leave a strange taste in your mouth for a few minutes. You might also feel that you need to urinate, but this sensation won’t last long.

The CT scanner is large and round like a doughnut. You will lie on a table that moves in and out of the scanner. It takes about 30 minutes to set up the machine, but the CT scan itself takes only 5–10 minutes.

The dye used in a CT scan usually contains iodine. If you have had an allergic reaction to iodine or dyes during a previous scan, let the person performing the scan know in advance. You should also tell the doctor if you’re diabetic, have kidney disease or are pregnant.

MRI scan

An MRI (magnetic resonance imaging) scan uses radio waves and magnetism to create cross-sectional pictures of the body. Sometimes, dye will be injected into a vein before the scan to help make the pictures clearer.

You will lie on a table that slides into a metal cylinder that is open at both ends. During the test, the machine makes a series of bangs and clicks and can be quite noisy.

Some people feel anxious lying in the narrow cylinder. Tell your doctor beforehand if you are prone to anxiety or claustrophobia. You may be given a mild sedative to help you relax.

Before arranging the test, your doctor will check your medical history. People who have a pacemaker or any other metallic object in their body usually cannot have an MRI due to the effect of the magnet. However, some newer pacemakers are MRI-compatible.

PET scan

During a PET (positron emission tomography) scan, you will be injected with a small amount of radioactive glucose solution. It takes 30–90 minutes for the solution to circulate around your body. You will be left alone in a small room and asked to rest quietly during this time.

Your body is then scanned for high levels of radioactive glucose. Cancer cells show up brighter on the scan because they are more active and take up more of the glucose solution than normal cells do.

Though it may take a few hours to prepare for a PET scan, the scan itselft usually takes only about 30 minutes. 


An ultrasound is a test that uses soundwaves to build up a picture of your body. A device (transducer or probe) is placed on or in your body. This sends out soundwaves that echo when they meet something dense, like a tumour, and images are projected onto a computer screen. Two types of ultrasounds may be used:

  • Abdominal ultrasound: This may be done to see whether bowel cancer has spread to the liver. A gel is spread over your abdomen to conduct the soundwaves, and the transducer is passed over the abdominal area to create the image. The test takes 15–20 minutes.
  • Endorectal ultrasound (ERUS): A probe is inserted through the anus into your rectum. This can be uncomfortable but is usually not painful, and there may be some light bleeding from the rectum. The test takes only about 10 minutes.

An ERUS is often done if other tests show there is cancer in the rectum or anus. It helps the doctor work out the size of the cancer, whether it has spread, and what treatments to recommend.

A chest x-ray may be taken to check if the cancer has spread to the lungs or lymph nodes in your chest.

Staging bowel cancer

The tests described above help show whether you have bowel cancer and whether it has spread. Working out how far the cancer has spread is called staging and it helps the doctor decide on the best treatment for you.

The most common bowel cancer staging systems are Australian Clinico-Pathological Staging (ACPS) and TNM (see opposite). When staging is done before surgery, it is known as clinical staging – it represents your doctor’s estimate of the extent of the disease and is based on the tests used to diagnose the cancer. Pathologic staging is based not only on those early tests, but also on tests on the cancer and lymph nodes removed during surgery (see treatment). These results are usually available about a week after the surgery.

Australian Clinico-Pathological Staging

Developed in Australia for bowel cancer, the ACPS system uses all available information to work out the cancer's stage.

Stage A Cancer is found only in the bowel wall.
Stage B Cancer has spread to the outer surface of the bowel wall.
Stage C Cancer has spread to the lymph nodes near the bowel.
Stage D Cancer has spread beyond the lymph nodes to other areas, such as the liver or lungs.
TNM staging

Used for many forms of cancer, the TNM system gives information about the tumour, nodes and metastasis. Each letter is assigned a number that shows how advanced the cancer is. If the letter X is used instead of a number, it means that it can’t be determined.

T (Tumour) 1-4 Indicates how far the tumour has grown into the bowel wall and nearby areas. T1 is a smaller tumour; T4 is a larger tumour.
N (Nodes) 0-2 Shows if the cancer has spread to nearby lymph nodes. N0 means that the cancer hasn't spread to the lymph nodes; N1 means there's cancer in 1-3 lymph nodes; N2 means cancer is in 4 or more lymph nodes.
M (Metastasis) 0-1 Shows if the cancer has spread to other, distant parts of the body. M0 means the cancer hasn't spread; M1 means the cancer has spread.


Prognosis means the expected outcome of a disease. You may wish to discuss your prognosis and treatment options with your doctor, but it is not possible for any doctor to predict the exact course of the disease. In most cases, the earlier bowel cancer is diagnosed and treated, the better the outcome.

To come up with a prognosis, your doctor will consider:

  • test results
  • the type of cancer you have
  • the rate and depth of tumour growth
  • how well you respond to treatment
  • other factors such as age, fitness and medical history. 

Which health professionals will I see?

Your GP plays a key role in your care throughout your treatment for bowel cancer. They will arrange the first tests to assess your symptoms, or further tests if you have had a positive FOBT. If these tests do not rule out cancer, you will usually be referred to a colorectal surgeon or a gastroenterologist, who will arrange more tests and treatment.

Health professional Role
GP explains information provided by specialists; assists you with treatment decisions; helps you obtain practical and emotional support; and works in partnership with your specialists in providing your ongoing care
colorectal surgeon diagnoses bowel cancer and operates on the bowel
gastroenterologist diagnoses bowel cancer and specialises in the digestive system and its disorders
medical oncologist prescribes and coordinates the course of chemotherapy
radiation oncologist prescribes and coordinates the course of radiotherapy
cancer care coordinator or clinical nurse consultant (CNC) supports patients and families throughout treatment and liaises with other members of your health care team
operating room staff include anaesthetists, technicians and nurses who prepare you for surgery and care for you during the operation and recovery

Once your treatment for bowel cancer begins, you will be looked after by a range of health professionals who specialise in different areas of your care.

The health professionals involved in your treatment will take a team-based approach and form a multidisciplinary team (MDT). The following health professionals may be in your MDT.

Health professional Role
nurses care for you during and after surgery; help administer drugs; and provide care, information and support throughout the course of your treatment
stomal therapy nurse (STN) provides information about surgery and adjusting to life with a temporary or permanent stoma
dietitian recommends an eating plan to follow while you are in treatment and recovery
genetic counsellor provides advice for people with a strong family history of bowel cancer or with a genetic condition linked to bowel cancer
social worker links you to support services and helps with emotional or practical issues
counsellor, psychologist provide emotional support and help manage depression and anxiety
physiotherapist, occupational therapist assist with physical and practical problems, including restoring range of movement after surgery

Key points

  • There are many types of tests used to diagnose bowel cancer, but you will only have the tests you need.
  • A faecal occult blood test (FOBT) checks stool samples for traces of blood. It is often done as part of a national screening program. The FOBT is for people with a low risk of bowel cancer and can help find polyps or bowel cancer in its early stages. If blood is found during the FOBT, you will probably have a colonoscopy. A colonoscopy can be used to look for polyps and cancer in the entire large bowel.
  • A flexible sigmoidoscopy is used to view the last 50 cm of the bowel. A rigid sigmoidoscopy looks at the rectum only.
  • A bowel preparation may be needed before some tests. This cleans out the bowel so the doctor can see clearly.
  • X-rays, CT scans, MRI scans, PET scans and ultrasounds are painless procedures that take pictures of the inside of your body. They may show the location of the cancer and whether it has spread.
  • The doctor will assign the cancer a stage. This describes the size and spread of the cancer. You may be told the stage of the cancer about a week after bowel surgery, when enough tissue and lymph nodes have been examined and tested.
  • Your prognosis is the expected outcome of the disease. The earlier bowel cancer is diagnosed and treated, the better the likely outcome.
  • You will probably see many health professionals who specialise in different areas of care and work together as a multidisciplinary team to diagnose and treat you.

Reviewed by: Mr Chip Farmer, Colorectal Surgeon, The Alfred Hospital, Cabrini Hospital and The Avenue Hospital, VIC; Mervyn Bartlett, Consumer; Dr Andrew Haydon, Medical Oncologist, The Alfred Hospital and Cabrini Hospital, VIC; Jackie Johnston, Palliative Care and Stomal Therapy Clinical Nurse Consultant, St Vincent’s Private Hospital (Darlinghurst), NSW; Dr Shahrir Kabir, Fellow in Colorectal Surgery, Royal Brisbane and Women’s Hospital, QLD; Steve Pratt, Nutrition and Physical Activity Manager, Cancer Council WA; Cassie Riley, Cancer Nurse Coordinator – Colorectal, WA Cancer and Palliative Care Network, WA; Mary Shanahan, Cancer Genetics Nurse Coordinator, Peter MacCallum Cancer Centre, VIC; A/Prof Andrew Stevenson, Head of Colorectal Surgery, Royal Brisbane and Women’s Hospital, University of Queensland; Pat Walls, Clinical Nurse Consultant Stomal Therapy/Wound Management, Holy Spirit Northside Private Hospital, QLD.
Updated: 01 Feb, 2015