The bowel
The large bowel (large intestine) is part of the digestive system. It has two major functions:
- to finish digesting food by absorbing water and nutrients
- to get rid of remaining wastes.
The large bowel has four main parts:
- Caecum - A pouch at the beginning of the large bowel that receives waste from the small bowel.
- Colon - The main working area of the large bowel, where water is removed. The colon is about 1.5 metres long and has four parts: the ascending colon, transverse colon, descending colon and sigmoid colon.
- Rectum - The last 15 to 20 centimetres of the large bowel. The rectum stores waste (stools) until they are expelled during a bowel movement
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How bowel cancer starts
Bowel cancer seems to start in two ways.
- It can grow from the inner bowel lining.
- It can grow from a small raised area that looks like a mushroom, called a polyp. Most polyps are harmless (benign) but some can become cancerous (malignant).
How common is it?
Bowel cancer is the second most common cancer affecting people in NSW. There are about 6,000 new cases of bowel cancer diagnosed each year. The older you are, the greater your chance of developing bowel cancer. While it affects mainly people over 50, bowel cancer can occur at any age.
What are the causes?
Some people who develop bowel cancer inherit damaged genes from their parents but, for most people, age and lifestyle factors (like eating habits) contribute to developing bowel cancer. Some people with inflammatory bowel disease have an increased risk.
Familial (hereditary) bowel cancer
If one or more of your family members (such as a parent or sibling) have been diagnosed with bowel cancer before age 55, it may run in your family. This is also a possibility if two relatives on the same side of your family have bowel cancer. If you are concerned that you have a family history of bowel cancer:
- Ask your GP about referral to a cancer genetics clinic so that your family situation can be considered in more detail
- Do regular physical activity, maintain a healthy weight and eat a diet high in fruit, vegetables and fibre.
Genetic conditions
About 5-6% of bowel cancers are caused by an inherited genetic condition.
One of those conditions, familial adenomatous polyposis (FAP), causes large numbers of polyps to form in the bowel. FAP is a rare condition, accounting for about 1% of colorectal cancers. Polyps are initially benign, but if they aren't removed, they will become cancerous.
Another genetic condition is called Lynch syndrome or hereditary non-polyposis colorectal cancer (HNPCC). Lynch syndrome accounts for about 3-5% of colorectal cancers. People with Lynch syndrome have an increased risk of developing certain types of cancer, including cancer of the colon or rectum. Women with this condition also have an increased risk of developing endometrial cancer (cancer of the lining of the uterus).
Turcot syndrome and Peutz-Jeghers syndrome are two rare inherited conditions in which those affected are at an increased risk of colorectal cancer.
Tests to diagnose bowel cancer
Before some diagnostic tests, you will have to clean out your bowel, which is known as bowel preparation. This is because stools impair the doctor's ability to see inside the bowel. Bowel preparation generally involves taking an oral laxative the day before the examination and having only clear fluids for 24-48 hours before the procedure.
If bowel preparation is required for your procedure you will be given clear instructions by your doctor.
Physical examination
Your doctor may feel your abdomen to check for swelling. The doctor will insert a gloved finger into the rectum to feel for anything unusual. May be a little uncomfortable.
Blood test
May be used to test general health and measure a molecule called carcinoembryonic antigen (CEA), which is produced in the bowel and by some cancer cells. CEA level is not always a reliable marker, so further tests may be done. Also may measure chemicals in the liver.
Faecal occult blood test
Blood in stool may be a symptom of bowel cancer. Some traces of blood can only be seen by a microscope. A faecal occult blood test (FOBT) can be done at home using a kit and then examined in a laboratory. You may have further tests.
Sigmoidoscopy
A rigid or flexible tube (sigmoidoscope) is put into the anus to examine the rectum and lower colon for cancer and other abnormalities. Takes 10-20 minutes. May be uncomfortable but should not cause severe pain. Your doctor may take a tissue sample (biopsy). May involve a bowel preparation before the test.
Colonoscopy
Used to look for signs of cancer and other abnormalities inside the entire colon. A long, flexible tube, with a tiny lens on the tip, is inserted through your anus and rectum then around your colon to its beginning at the small bowel. Before the test, you will have a bowel preparation to clean your bowel. You will be given a sedative or anaesthetic that will make you feel drowsy. You may feel some discomfort during or after the procedure but this should settle quickly. During the colonoscopy, the doctor can remove polyps and take out tissue (a biopsy) to test for cancer. Arrange to have someone take you home, as you may still be feeling drowsy after the colonoscopy. Takes 20-30 minutes.
Virtual colonoscopy
Type of CT scan that produces a picture of the colon. Less invasive than a regular colonoscopy. Beforehand, you may have a bowel preparation to clean out your bowel. Doesn’t allow polyps or cancer to be removed or biopsied. If a virtual colonoscopy shows a problem, more tests may be needed.
Barium enema
Type of x-ray investigation. Beforehand, you will have a bowel preparation to clean out your bowel. A small liquid-filled tube is inserted into your rectum. The tube is filled with a liquid enema that contains special fluid (barium) that shows up on x-rays. Can be a little uncomfortable. Takes about 30 minutes
Abdominal ultrasound
Uses soundwaves to build up images of your body. A small device (called a transducer) is moved over your abdomen. The liver in particular is checked for signs of cancer. Soundwaves echo when they hit something dense, like an organ or tumour. Painless. Takes 15-20 minutes.
Endorectal ultrasound
Used if other tests find cancer in the rectum or anus. A small device (called a probe) is inserted into the rectum. Soundwaves from the probe create pictures on a computer screen. Takes about 10 minutes. Not painful but can be uncomfortable. Can also help the surgeon plan surgery and to see whether any extra treatment, such as radiotherapy, is needed.
CT (computerised tomography) scan
An exam that uses x-rays to take pictures of the inside of your body. You will lie flat on a table while the CT scanner, which is large and round like a doughnut, moves around you and takes pictures. You may have an injection of dye into your veins before the scan -- this will make pictures clearer. Used to see if the cancer has spread. Painless. The scan itself takes 5-10 minutes.
MRI (magnetic resonance imaging) scan
Scan uses a combination of magnetism and radio waves to build up detailed cross-section pictures of your body. Involves lying on a table inside a metal cylinder - a large magnet - that is open at both ends. You may have an injection of dye into your veins before the scan - this will make the pictures clearer. Painless. Some people find lying in the cylinder noisy and claustrophobic. If you feel uncomfortable, let your doctor or nurse know.
PET (positron emission tomography) scan
Specialised imaging test that may be used to determine if cancer has spread. You are given a radioactive glucose solution, and it will circulate your body for 30 to 90 minutes. Your body is scanned -- active cells, like cancer cells, have an increased uptake of radioactive glucose. May take several hours.
Stages of bowel cancer
Working out how far the cancer has spread is called staging. Staging helps your doctor recommend the best treatment for you. Doctors can estimate the stage of your cancer, or if tissue is removed (biopsied), your doctor may be able to give you a more accurate stage.Doctors commonly use an international staging system called TNM:
- T - refers to tumour size
- N - describes if cancer has spread to the lymph nodes
- M - describes whether the cancer has spread to another part of the body (metastasised).
Prognosis
Prognosis means the expected outcome of a disease. Generally, the sooner bowel cancer is diagnosed, the better the prognosis. You will need to discuss your prognosis with your doctor. It is not possible for any doctor to predict the exact course of your illness. Test results, the rate and depth of tumour growth, how well you respond to treatment, and other factors such as age, general health and your medical history are all important factors in assessing your prognosis.
Treatment
For many people surgery is the main treatment for bowel cancer. The surgeon will cut out the part of the bowel with cancer and then join the two ends of the bowel. If the bowel can't be joined, you will have a stoma. Some people have minimally invasive surgery - this is a term that describes surgical techniques using smaller cuts. This is sometimes called laparoscopic or keyhole surgery. Whether or not you can have minimally invasive surgery depends on the location of the cancer and its size. Recovery time varies, depending on the extent of surgery.
You may have looser and more frequent bowel movements. Bowel function usually improves and becomes more normal over a few months. If this remains a problem discuss things with your doctor or nurse.
You may find some foods cause you discomfort and it can be helpful to see a dietician.
Surgery for colon cancer
The aim of colon cancer surgery is to remove the cancer and enough of the surrounding tissue to ensure no microscopic cancer is left behind. The most common type of surgery is called a colectomy. The five main types are:
- right hemicolectomy - cancer from the right side is removed
- left hemicolectomy - cancer from the left side is removed
- transverse colectomy - cancer from the middle is removed
- sigmoid colectomy - cancer in the sigmoid colon is removed
- subtotal or total colectomy - most or all of the bowel is removed.
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Another type of surgery is called a high anterior resection. In this operation, a section of the lower bowel is removed and the remaining parts of the bowel are rejoined in the upper rectum.
Side effects
You will have a scar, usually running from your navel to pubic area. Depending on how much bowel is removed, you may have to open your bowels more often or you may have diarrhoea. You may need a temporary colostomy (stoma). If your surgeon can't reconnect the healthy parts of your bowels, the large bowel will be connected to a permanent opening (stoma) on your body.
Treatment for rectal and anal cancers
There are three main types of surgery for cancer in the rectum or anus:
- Anterior resection: The surgeon cuts into the abdomen, or minimally invasive (keyhole) techniques are used. The cancer and surrounding tissue, including nearby lymph nodes are removed. The ends of the bowel are rejoined.
- Ultra-low anterior resection: the entire rectum is removed and an internal pouch (colonic J-pouch) is created using small bowel tissue. This pouch will be connected to the anus and work as a rectum. If you have a J-pouch, you will have less frequent bowel movements after surgery.
- Abdominoperineal (AP) resection: A less common type of rectal surgery. The rectum and anus are removed. Afterwards, you will have two wounds: one on the abdomen and one where the anus was removed. You will have a permanent stoma (colostomy).
For rectal cancer radiotherapy is often given before surgery, and is generally given along with chemotherapy. This is known as chemo-irradiation. Having this treatment before surgery makes it easier to remove the cancer and lowers the risk that the cancer will recur.
Many anal cancers are no longer treated with surgery. Radiotherapy given along with chemotherapy is more effective in curing the cancer and results in fewer side effects.
Local excision - A tube is inserted into the rectum and lower colon and cancer is removed without cutting into the abdomen. There are several types of local excision - for example, a polypectomy is when the surgeon cuts out a polyp.
Transanal resection - when the surgeon doesn't cut into the muscle controlling the opening and closing of the anus (sphincter).
Other treatments
The type of treatment you have depends on your doctors' recommendations and what you want. No matter what you do, it is important to have regular checkups for the rest of your life. This is because people who have had bowel cancer have a higher than average chance of developing another primary cancer but also allows your doctor to examine you to see if your cancer has come back and to assess and manage any side effects you have as a result of your treatment.
Which health professionals will I see?
You will be cared for by a range of health professionals who specialise in different aspects of your treatment. This multidisciplinary team will probably include:
- surgeon - either a colorectal surgeon or general surgeon who specialises in bowel care
- radiation oncologist - responsible for radiotherapy
- medical oncologist - responsible for chemotherapy
- gastroenterologist - specialises in the digestive system and its disorders
- nurses - assist you through all stages of your treatment
- stomal therapy nurse - provides information about surgery and adjusting to life with a stoma
- cancer care coordinators - facilitate the continuity and quality of your care and support you and your family throughout your treatment
- dietician - supports and educates patients about nutrition and diet
You may also see the following:
- social workers, physiotherapists and occupational therapists - link you to support services and help you get back to your normal activities
- counsellor, psychologist and psychiatrist – provide emotional support and help manage anxiety and depression
- genetic counsellor - provides advice for people with a strong family history of bowel cancer
Your general practitioner (GP) is an important member of your treatment team. GPs can explain information provided by your specialists, help you with treatment decisions and assist you in obtaining practical and emotional support.