Diseases of the colon
colon cancer
Colorectal cancer includes cancerous growths in the colon, rectum and
appendix. It is the third most common form of cancer and the second
leading cause of death among cancers in the Western world. Many colorectal
cancers are thought to arise from polyps in the colon. These mushroom-like
growths are usually benign, but some may develop into cancer over time.
Diagnosis is by colonoscopy. Therapy is usually through surgery, with
many cases also requiring chemotherapy.
Symptoms:
Symptoms of colorectal cancer include:
Change in bowel habits.
Blood in stools (melena, hematochezia).
Bowel obstruction (rare) by the tumor
Often, the symptoms are much less specific:
Unexplained weight loss.
Anemia, with symptoms such as tiredness, malaise, pallor
Hepatomegaly (enlargement of the liver) due to speading of the tumor
It is also possible that there will be no symptoms at all. This is one reason why some recommend periodical screening for the disease.
Risk factors:
The lifetime risk of developing colon cancer in the United States is about 7%. Certain factors increase a person's risk of developing the disease. These include:
Age. The risk of developing colorectal cancer increases with age. Most cases occur in the 60's and 70's, while cases before age 50 are uncommon unless a family history of early colon cancer is present.
History of cancer. Women who have had cancer of the ovary, uterus, or breast are at higher risk of developing colorectal cancer.
Heredity:
Family history of colon cancer, especially in a close relative before the age of 55 or multiple relatives.
Familial adenomatous polyposis (FAP) carries a near 100% risk of developing colorectal cancer by the age of 40 if untreated
Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome.
Long-standing ulcerative colitis or Crohn's disease of the colon, approximately 30% after 25 years if the entire colon is involved.
Smoking. Smokers are more likely to die of colorectal cancer than non-smokers.
Diet. Some studies have shown that people who have diets high in fresh fruit and vegetables and low in red meat are at reduced risk of colorectal cancer.
Physical inactivity. People who are physically active are at lower risk of developing colorectal cancer.
Virus. Exposure to some viruses (such as human papilloma virus) may be associated with colorectal cancer.
Diagnosis, screening and monitoring:
Indentification of malignancy
Colorectal cancer can take many years to develop and early detection of colorectal cancer greatly improves the chances of a cure. Therefore, screening for the disease is recommended in individuals who are at increased risk. There are several different tests available for this purpose.
Digital rectal exam (DRE): The doctor inserts a lubricated, gloved finger into the rectum to feel for abnormal areas. It only detects tumors in the distal part of the rectum.
Fecal occult blood test (FOBT): a test for blood in the stool.
Endoscopy:
Sigmoidoscopy: A lighted probe (sigmoidoscope) is inserted into the rectum and lower colon to check for polyps and other abnormalities.
Colonoscopy: A lighted probe called a colonoscope is inserted into the rectum and the entire colon to look for polyps and other abnormalities that may be caused by cancer. A colonoscopy has the advantage that if polyps are found during the procedure they can be immediately removed. Tissue can also be taken for biopsy.
Double contrast barium enema (DCBE): An enema containing barium sulfate, which helps the outline of the colon and rectum stand out on X-rays, is given to the patient. The doctor then takes a series of X-rays of the colon and rectum.
Virtual colonoscopy can image the colon using x-rays and is approaching colonoscopy in sensitivity for polyps. However, any polyps found must still be removed by standard colonoscopy.
Computed axial tomography is an x-ray method that can be used to determine the degree of spread of cancer, but is not sensitive enough to use for screening. Some cancers are found in CAT scans performed for other reasons.
Blood tests: Measurement of the patient's blood for elevated levels of certain proteins can give an indication of tumor load. In particular, high levels of carcinoembryonic antigen CEA in the blood can indicate metastasis of adenocarcinoma. These tests are frequently false positive or false negative, and are not recommended for screening.
Genetic counseling and genetic testing for families who may have a heriditary form of colon cancer, such as Hereditary nonpolyposis colorectal cancer (HNPCC) or Familial adenomatous polyposis (FAP).
Positron emission tomography (PET) is a 3-dimensional scanning technology where a radioactive sugar is injected into the patient, the sugar collects in tissues with high metabolic activity, and an image is formed by measuring the emission of radiation from the sugar. Because cancer cells often have very high metabolic rate, this can be used to differentiate benign and malignant tumors. PET is not used for screening and does not (yet) have a place in routine workup of colorectal cancer cases.
Pathology:
The pathology of the tumor is usually reported from the analysis of tissue taken from a biopsy or surgery. A pathology report will usually contain a description of cell type and grade. The most common colon cancer cell type is adenocarcinoma which accounts for 95% of cases. Other, rarer types include lymphoma and squamous cell carcinoma.
Cancers on the right side (ascending colon and caecum) tend to be exophytic, that is the tumour grows outwards from one location in the bowel wall. This very rarely causes obstruction of feces, and present with symptoms such as anemia. Left-sided tumours tend to be circumferential, and can obstruct the bowel much like a napkin ring.
Alternative therapies:
The agents listed here are not proven in clinical trials but may be considered to have anti-colon cancer properties in in-vitro studies, the popular press, folk medicine or other sources.
Ginger
Curcumin (Turmeric anti-angiogenesis factor)
Mistletoe extract (as solid tumor reducer)
Acupuncture (symptom reduction)
Support therapies:
Cancer diagnosis very often results in an enormous change in the patient's sociological wellbeing. Various support resources are available from, hospitals and other agencies which provide counseling, social service support, cancer support groups, and other services. These services help to mitigate some of the difficulties of integrating a patient's medical complications into other parts of their life.
http://en.wikipedia.org/wiki/Colon_cancer