Colorectal cancer

What is colorectal cancer?

The colon and the rectum are parts of the large intestine. The intestine is an organ that helps in digestion and excretion. Digestion is mainly carried out by the small intestine, while excretion is the major function of the large intestine. A malignant growth of cells in the large intestine is called colorectal cancer. Separately, the cancer may be of the colon (colon cancer) or the rectum (rectal cancer).

What are the causes?

Like most cancers, the exact cause of colorectal cancer is not known. However, there are certain risk factors that predispose an individual to it. These are:

• Age – risk increases with age.
  
• A diet high in fat but low in fibre.
  
• The presence of some kinds of polyps, which are benign growths in the intestine. These growths present on the wall of the intestine are not harmful by themselves, but if present in large numbers may be a leading cause of colorectal cancer.
  
• As with all cancers, a family history of colorectal cancer.
  
• A condition affecting the colon called ulcerative colitis, in which the colon becomes red and inflamed.
  

What are the symptoms?

Colorectal cancers may produce no symptoms till the disease is advanced. However, the most frequently noted symptoms that may be indicative of the disease are:

• Passage of bright red or dark coloured blood in the stools
  
• Change in bowel habits with frequent diarrhoea or constipation
  
• Change in the appearance of stools
  
• Constant feeling of fullness or gas in the stomach
  
• Persistent feeling that the bowel is not being cleared fully
  
• Unexplained loss of weight sometimes accompanied by anaemia
  
• Fatigue and tiredness.

How is it diagnosed?

A thorough examination of the patient’s medical history is done in addition to a physical check-up. The doctor may also prescribe certain tests for confirmation. An X-ray of the intestine, called a barium enema, helps the doctor to detect the presence of any abnormal growths or cysts.

Colonoscopy or sigmoidoscopy may be done, which allow the doctor to see inside the colon and the rectum for detection of polyps or cysts. A thin, flexible tube-like telescope is inserted through the rectum into the intestine. A small sample of the area may be taken for biopsy with the helps of forceps attached to the instrument. In some cases, any polyps that are detected may also be removed simultaneously by burning them.

What is the treatment?

Surgery to remove the tumour is the most common form of treatment. If the tumour has not spread to other parts of the organ, it can be easily removed. Mostly some healthy parts of the intestine are also removed to reduce the risk of recurrence. Sometimes, a surgical procedure called colostomy is performed. This is done if the surgeon, after removing parts of the colon is unable to join it back with the rectum. In this, the colon opens in the skin of the abdomen, to allow faecal matter to drain and be collected in a bag. This procedure may be temporary or permanent.

In some cases with wide-spread disease, chemotherapy is given to destroy the cancer cells. Radiation therapy may also be done in some cases if the tumour is localized.

Treatment may have side effects like pain in the area after partial removal of the colon. The usual side effects of chemotherapy like hair loss, nausea and vomiting may also be present. There may also be loss of appetite and loss of weight after the treatment procedures.