Colonoscopy is a procedure that enables the examiner to view the inside of the large bowel. This is accomplished by passing a flexible video-endoscope through the anus into the rectum, then advancing slowly through sigmoid colon, descending colon, transverse colon, ascending colon and lastly to the caecum. The examiner can have direct vision of the colon or pathological changes inside the colon, such as tumor, ulceration or polyps. Doctor may take biopsy for pathological examination, perform polypectomy and therapeutic hemostasis when necessary.
Colorectal cancer
Colon cancer is one of the most common types of cancer. It is very treatable, if caught early. Risk factors of colon cancer include age, family history of colon cancer, patients with ulcerative colitis, or Crohn’s disease.
Physical inactivity, high fat and low fiber diet, long-term alcohol and tobacco use, and obesity are all contributing factors to the development of colon cancer. Some of the symptoms may include changes in bowel habits (constipation or diarrhea), blood in the stool, abnormal weight loss, and abdominal pain.
According to figures from the Department of Health, colorectal cancer ranked second among all fatal cancers in Hong Kong. In 2016, the number of people who died because of colorectal cancer totaled 2,089, which accounted for approximately 15% of all cancer-related deaths locally.
Colonoscopy can also be part of a routine screening for people who have a family history of colon cancer or polyps (non-cancerous growths in the lining of the colon), and as screening for inflammatory bowel diseases such as Crohn’s disease or ulcerative colitis. It can also be used to remove colon polyps and to take a biopsy (small tissue of the lining of the colon) for examination under the microscope to identify an infection.
Colorectal cancer may be benign or malignant. A malignant cancer can spread to other parts of the body, so screening can detect polyps before they become cancerous during its early stages when the chances of a cure are much higher.
Fecal occult blood tests (blood stool tests) and stool DNA tests (testing for certain DNA markers) are non-invasive and convenient, but they cannot detect tumors that are not bleeding or showing DNA mutations. The best method to clearly inspect the entire large bowel is through colonoscopy. If polyps are discovered, they can be removed immediately. Early detection and removal of polyps can lower the chances of colorectal cancer by 3 to 8 times. According to the Department of Health, for carriers of the mutated gene for Lynch syndrome, lifetime risk of colorectal cancer is estimated to be as high as 50-80%. For carriers of the mutated gene for familial adenomatous polyposis, there is nearly 70-100% lifetime risk of colorectal cancer.
