Colorectal
Where is the colon and rectum? chinese
The colon and rectum (or the large intestine) is the last part of the gastrointestinal tract. Broadly our gastrointestinal tract consists of
Oesophagus which connects the mouth to the stomach where the food is stored and released periodically into the small intestine where the food is broken down and absorbed. The food residue enters the colon where water is absorbed and the food residue is converted to waste product by the action of bacteria. The rectum is the terminal part of the colon in which the waste produce (faeces) is stored before being expelled via the anus.
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What is colorectal cancer?
Colorectal Cancer is also otherwise known as colon cancer or bowel cancer. It refers to a growth that first forms inside the colon or the rectum.Our body is made up of basic units called cells. When these cells grow in an uncontrolled manner, a malignant growth or a cancer is formed.
Colorectal cancer is formed from cells which line the inner wall of the colon and rectum. This lining is called the mucosa. At this stage the cancer is termed non-invasive i.e. the cancer cells have not spread out of the colon. If undetected, the cancer will grow bigger and project into the lumen of the colon. It will also invade through the colon wall and spread via several routes:
1. Invasion of neighbouring intestines and organs
2. Lymphatic system into neighbouring lymph glands called mesenteric lymph nodes.
3. Blood stream to the liver where secondary malignant deposits can be formed.
Colorectal cancer that has invaded the lymph nodes or the liver is in the advanced stage.
What are polyps?
There is no single cause of colorectal cancer, as in most cases, colon cancers begin as a polyp that develops into a cancerous growth.
Polyps are benign lumps on the inner wall of the colon and rectum. They look like a small grape attached to the colon by a stalk. They are fairly common in people above 50 years old. Some types of polyps (called adenomatous polyps) may transform into cancer. If such polyps are detected, they should be removed to prevent the development of cancer.
Normal Colon
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Colon with Polyp
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Certain features of a polyp make one suspect that it may be malignant:
- Polyp > 1 cm diameter
- Sessile polyps (i.e. polyps without a stalk)
- Multiple polyps
What Causes It?
No one knows the exact causes of colorectal cancer. However, we do know that people with certain are more likely than others to develop colorectal cancer. Studies have found the following risk factors for colorectal cancer:
- Colorectal polyps: Polyps are growths on the inner wall of the colon or rectum and is common in people over age 50. Most polyps are benign (not cancer), but some polyps (adenomas) can become cancer.
- Ulcerative colitis or Crohn’s disease: A person who has had a condition that causes inflammation of the colon (such as ulcerative colitis or Crohn’s disease) for many years is at an increased risk.
- Personal history of cancer: A person who has already had colorectal cancer may develop colorectal cancer a second time. Also, women with a history of cancer of the ovary, uterus (endometrium), or breast are at a somewhat higher risk of developing colorectal cancer.
- Family history of colorectal cancer: If you have a positive family history of colorectal cancer, you are more likely than others to develop this disease, especially if your relative had the cancer at a young age.
- Lifestyle factors: Individuals who smoke, or consume a diet that is high in fat and low in fruits and vegetables are at an increased risk of colorectal cancer
- Age over 50: Colorectal cancer is more likely to occur as people get older. More than 90 percent of people with this disease are diagnosed after age 50 years and above.
Symptoms
A common symptom of colorectal cancer is a change in bowel habits. Symptoms include:
- Change in bowel habits (diarrhea or constipation)
- Feeling that your bowel does not empty completely
- Finding blood (either bright red or very dark) in your stool
- Finding your stools are narrower than usual
- Frequently having gas pains or cramps, or feeling full or bloated
- Losing weight with no known reason
- Feeling very tired all the time
- Having nausea or vomiting
Most often, these symptoms are not due to cancer. Other health problems can cause some of these symptoms. Additionally, it is important to note that early cancer does not usually cause pain. Therefore, anyone with these symptoms should see a doctor to be diagnosed and treated as early as possible.
Screening
Colorectal cancer is the most common cancer in Singapore, but the symptoms are not always obvious in the early stages. Fortunately it can be detected and treated early, and the chances of recovery are high.
Screening tests help your doctor find polyps or cancer before you have symptoms. Early detection of colorectal cancer will also improve effectiveness of cancer treatment. The following screening tests can be used to detect polyps, cancer, or other abnormalities.
- Fecal occult blood test (FOBT): Sometimes cancers or polyps bleed, and the FOBT can detect tiny amounts of blood in the stool. This is a preliminary screening test for colorectal cancer, which is cancer of the colon and rectum. It tests for presence of blood in the stools. Those 50 years and older are advised to have a faecal occult blood test done annually. If this test detects blood, other tests are needed to find the source of the blood. Benign conditions (such as hemorrhoids ), can also cause blood in the tool.
- Sigmoidoscopy: Your doctor examines your rectum and the lower part of the colon with a lighted tube (sigmoidoscpe). If polyps (benign growths that may lead to cancer) are found, they may be removed.
- Colonoscopy: Your doctor examines your rectum and entire colon using a long, lighted tube (colonoscope). If polyps (benign growths that may lead to cancer) are found, they may be removed.
- Double-contrast barium enema: This procedure involves filling the colon and rectum with a white liquid material (barium) to enhance x-ray pictures. Abnormalities (such as polyps) can be seen clearly.
- Digital rectal exam: A rectal examination is often part of a routine physical checkup. Your doctor inserts a lubricated, gloved finger into your rectum to feel for any abnormalities.
Diagnosis
If you have a symptom or screening result that suggests colorectal cancer, your doctor must find out whether it originates from cancer or other health conditions.
Your doctor will ask about your personal and family medical history and perform a physical examination.
If abnormalities (such as polyps) are found, a biopsy may be required. Often, the abnormal tissue can be removed during colonoscopy or sigmoidoscopy. A pathologist checks the tissue for cancer cells using a microscope.
How is Colorectal Cancer Assessed?
If the biopsy shows that cancer is present, your doctor needs to know the extent of the disease to plan the best treatment. The stage is based on whether the tumor has invaded nearby tissues, whether the cancer has spread and, if so, to what parts of the body.
Doctors describe colorectal cancer by the following stages:
| Stage 0 : |
The cancer is found only in the innermost lining of the colon or rectum. Carcinoma in situ is another name for Stage 0 colorectal cancer. |
| Stage l : |
The tumor has grown into the inner wall of the colon or rectum. The tumor has not grown through the wall. |
| Stage ll : |
The tumor extends more deeply into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes. |
| Stage lll : |
The cancer has spread to nearby lymph nodes, but not to other parts of the body. |
| Stage IV : |
The cancer has spread to other parts of the body, such as the liver or lungs.
- Recurrence: This is cancer that has been treated and has returned after a period of time when the cancer could not be detected. The disease may return in the colon or rectum, or in another part of the body.
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What Treatment is offered?
- Surgery – Surgery involves the removal of tissues that contain the tumor and nearby tissues/lymph nodes. This may be done via laparoscopy or open surgery.
- Chemotherapy – Chemotherapy uses anticancer drugs to shrink/kill cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body.
- Biological Therapy – Some people with colorectal cancer that has spread receive a monoclonal antibody, a type of biological therapy. The monoclonal antibodies bind to colorectal cancer cells. They interfere with cancer cell growth.
- Radiation Therapy – Radiation therapy (also called radiotherapy) uses high-energy rays to kill cancer cells. It affects cancer cells only in the treated area.
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