Dr Israel Dube MBChB, MMed (Surgery), FCS (ECSA)
The colon, also called the large intestine is the last part of the intestines where the body extracts water and salt from solidifying stool. The right colon is wider than the left and also the contents are more liquid on the right and more solid on the left.
Normal body cells follow an orderly process of growth, adhering to other cells, division and death. Cancer cells occur when cells grow and divide uncontrollably, without dying and have the propensity to move to other areas.
Cancer in the colon is very common and especially now, it seems more people are getting it than in the past. “A western” type diet has been partly to blame for this and a healthy lifestyle with high fibre, low-fat can help prevent colon cancer and screening can actually detect it early.
Most cancerous cells start from the inner lining of the colon. These cells become out-of-control and start multiplying rapidly. Most cancers originates from non-cancerous or benign growths in the colon called polyps (adenomatous polyps) that form in the inner lining of the colon. These cells grow and invade normal healthy tissues around them and as time goes by can spread to other tissues throughout the body, in a process called metastasis. The result is a more serious and less treatable condition.
Initially, there are often no symptoms in the early stages. As the cancer advances the following may be seen. Right and left colon give different symptoms.
- Constipation or diarrhoea;
- Changes in stool consistency,
- Narrow stools;
- Blood in stool;
- Abdominal pain or cramps;
- Bloating or passing lots of gas;
- Pain on passing stool;
- Continual urges to pass stool;
- Weakness or fatigue;
- Unexplained weight loss;
- Iron deficiency anaemia.
If the cancer spreads to a new part of the body then additional symptoms occur. The liver is most commonly involved.
Exact causes are unknown but cancer has several risk factors:
Habbits Diet Age
Cancer is more likely in people with sedentary lifestyles. Lifestyle is more important in causing cancers than genetic makeup. Obesity increases the risk. Smocking also increases risk.
As we age the cancer risk increases. Around 91 percent of colonic cancers occur in people over 50-year-old. Peak age in the 7th decade of life.
Diets low in fiber, red meats, alcohol and processed meats have been linked to higher risk.
Villous adenomas can become cancerous while tubular adenomas rarely become cancerous. These polyps can easily be removed during colonoscopy.
A genetic predisposition can be inherited from parents. Interestingly, most cancers occur in people without a family history. Sometimes, a person can have genes to develop cancer but this may only happen when an environmental factor triggers it!
Some medical conditions and certain treatments have been linked to increased colonic cancer risk e.g:
- Inflammatory bowel diseases like ulcerative colitis/crohn’s disease;
- Intra-cavity-radiation treatment for cervical cancer;
- After certain operations like uretersigmoidostomy, stomach surgery or cholecystectomy;
- Long-term immunosupression in HIV, diabetes or prevention of transplant rejection.
A health worker will usually get a detailed history of symptoms, personal and family medical histories and do a complete physical examination with a rectal digital examination. Tests, including blood tests, colonoscopy, ultrasound scan, barium enema, CT colonography. Diagnosis is usually confirmed with biopsy.
This is a long flexible thin tube with a camera on one end and is inserted into the anus and easily inspects the inside of the colon.
A special diet may be given for 24-48hrs before and some bowel cleansing with strong laxatives makes the inspection easier.
A sedative is usually given and the inspection is done as a day case in most cases i.e. coming from home. If polyps are seen they are removed and sent for laboratory testing by a pathologist.
A similar test can be done using a shorter scope which only shows the last bits of the colon (flexible sigmoidoscopy). A rigid tube can also be used but this needs a general anaesthetic.
Double Contrast Barium Enema
An X-ray procedure using a liquid called barium. You must fast before the test. The barium is injected into the colon through the anus using a small tube. Air is also put in to optimise results
This is a specialised scan using X-rays and utilises a computer to take multiple X-rays and reconstruct the areas wanted into slices throughout the body parts. A fluid, unlike barium, can be injected into the colon and the whole colon can be seen very clearly.
This test will also see all the other organs in the abdomen/pelvis including areas where cancer has invaded and if liver is involved. It can stage the disease.
Staging the Cancer
The stage of the cancer is a way of using the size and extent of the tumour, involvement of different organs and lymph nodes and combining this with all the knowledge currently known and how people have responded in the past to different treatments we can see which will be the best treatment combinations, how aggressive should we be at that stage or later and also what are the chances of the person with that extent of cancer surviving to usually 5years and or chances of getting a cure from the cancer.
There are various staging systems but the easiest and commonest stages cancer from 1 to 4
Stage 1: Tumour still confined to the inner layers of the colon with no spread.
Stage 4: Cancer has spread to distant parts of the body.
Cancer treatment needs a team approach to maximise results. There is no single treatment for any cancer. Usually surgery, chemotherapy, immunotherapy, radiation and palliation therapy with counselling are parts of treatments. Removing the growth is just part of the treatment. To maximise results the team combines the histories taken, health status, tests done, type of the cancer (actual or perceived) and see what will be the best way forward for each individual patient!
Part of the colon (if half- hemicolectomy)or all (total colectomy) can be removed. Sometimes a stoma (opening made in the wall of the abdomen so that the waste goes into a bag) is made temporarily or for life, depending on the cancer site. Sometimes no stoma is made.
These are drugs that interfere with cell division and will target rapidly dividing cells including some healthy ones. Healthy normal cells usually recover.
This treatment damages and kills cancer cells by focusing high-energy gamma rays on them
Prevention and Outlook
Prevention and screening remain the most important ways to combat colon cancer.