26 January 2008

Colon Cancer

Colon Cancer Introduction
The human colon is a muscular, tubular in the abdominal cavity. It has four sections :-
  1. Ascending colon - It extends upward on the right side of the abdomen.
  2. Transverse colon - It goes across the body from left to right.
  3. Descending colon - It continues downwards in the left side.
  4. Sigmoid colon - S-shaped part, which joins the rectum.
The right side of the colon absorbs water and electrolytes from fecal material to concentrate it. While the left side stores and empty stool.

Colon cancer is a disease in which malignant cells in the lining or epithelium of the colon develop. Those malignant cells are characterized by their inability to control their growth and their ability to invade surrounding tissues and spread throughout the body.

Signs & Symptoms
Most of the symptoms caused by colon cancer are due to its physical existence. These symptoms may include one or more of the following :-
  • Changes in the bowel habits such as diarrhea, constipation, or narrowing of the stool.
  • Rectal bleeding or blood in the stool may be observed.
  • Sensation of incomplete evacuation after a bowel movement.
  • Weakness and fatigue.
  • Weight loss.
  • Loss of appetite.
  • Jaundice of the skin or sclera of the eye.
  • Nausea and vomiting.
Methods of Diagnosis
First of all, medical history is checked to identify any risk factors. Then some laboratory tests are carried out. Laboratory tests may include :-
  1. Urinalysis
    This test is made to detect microscopic hematauria.
  2. Urine Cytology
    In this test urine is examined under a microscope to look for any abnormal or cancerous cells.
  3. Urine Culture
    In this test a sample of urine is tested in the lab to check for the presence of bacteria and hence to rule out urinary tract infection as the cause of urinary symptoms.
  4. Cystoscope
    Thin, telescope-like tube with a tiny camera attached is inserted into the bladder through the urethra to allow the physician to view the inside of the bladder. If any abnormal masses are seen, biopsy test is carried out.
  5. Biopsy
    A small piece of tissue is removed from the abnormal mass using a pair of biopsy forceps. Then, the tissue is examined under the microscope to check if it is cancerous.
  6. Intravenous Pyelogram (IVP)
    It is the standard imaging test for bladder cancer. In this procedure, a dye is injected into the bloodstream and x-rays are taken as the dye moves through the urinary tract. IVP provides information about the structure and function of the kidneys, ureters, and bladder and hence determine any abnormalities in their linings.
Risk Factors
  • Age
    Although it may occur at any age, colon cancer occurs usually in people over the age of 50.
  • Diet
    Diet high in fat, red meat, calories and alcohol seem to increase the risk of developing colon cancer. On the contrary, high-fiber diet seems to decrease its risk.
  • Polyps
    Benign growths on the colon lining, they usually precede the development of colon cancer.
  • Ulcerative Colitis
    Ulcerative colitis is an inflammatory bowl disease that causes swelling, ulcerations, and loss of function of the colon and large intestine. People who have ulcerative colitis have an increased risk of developing colon cancer.
  • Hereditary Predisposition
    The susceptibility to develop colon cancer may be inherited. People with first degree relatives who have had colon cancer have an increased risk of developing it.
  • Smoking
    Smoking increases the risk of developing colon cancer.
  • Obesity
    Obesity increases the risk of developing colon cancer.
Treatments
Treatment of colon cancer differs from patient to patient depending on patients age, health, medical history, extent of disease and tolerance for certain medications and procedures. First of all the malignant tumor must be found and staged. Then, depending on this stage and the above mentioned factors, the doctor will suggest a treatment plan.

Treatment may include :-
  1. Surgery
    It is used as primary therapy for stages I through III colon cancer [as mentioned in Cell Transformation section] as long as there is no local invasion. In surgery, the involved segment of the colon is removed (colectomy) with its blood supply and lymph nodes. This colostomy is done by bringing the end of the colon through the abdominal wall and sewing it to the skin. The patient will have to wear a bag to manage the stool.
  2. Radiation Therapy
    It is usually used after surgery to kill any small areas of cancer that are not removed by surgery. There are two types of radiation: external beam radiation, where radiation is focused on cancer from outside the body, and internal radiation therapy, where pellets of radioactive material are directly placed into the cancer.
  3. Chemotherapy
    It involves the use of anticancer drugs. Those drugs are either given by mouth or into a vein to kill cancer cells throughout the body. The drug 5-flourouracil is an examples of anticancer drugs used to treat colon cancer.
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