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A colonoscopy is a specialised examination that allows your doctor to look inside your large intestine for a complete large bowel evaluation. The colonoscope is a flexible tube about the thickness of a finger with a camera attached to one end. It contains 2 narrow channels to allow the endoscopist (doctor performing the colonoscopy) to suck out any fluid from the colon and insert a grasping instrument to remove any polyps or take biopsy. The colonoscopy is inserted from the anus and carefully maneuvered through the rectum into the colon.
Indications for colonoscopy
Colonoscopy helps your doctor evaluate symptoms of the lower digestive tract, to find out if your large intestine is healthy or diseased. If needed, treatment can also be performed through the colonoscope, such as removal of polyps (polypectomy). The common indications for colonoscopy are listed below.
  1. Bleeding from the anus
  2. Anal itch
  3. Change in bowel habit pattern (e.g. change in colour, frequency of bowel movement, size of stools) persisting for more than 2 weeks
  4. Constipation
  5. Diarrhoea
  6. Family history of colorectal (bowel) cancer
  7. Family history of colorectal polyps
  8. Anaemia  or pallor
  9. Screening for colorectal cancer (for people above the age of 50 years)
Preparations for Colonoscopy
The doctor will check the medications you are currently taking and guide you accordingly. Some medications may need to be stopped before the colonoscopy. You will receive instructions in advance to help you prepare for this test. You will have to stop taking any dietary fiber (fruits, vegetables, mushrooms) for one day before the test. You will be given a purgative medication to clean out your large intestine, so that clear views can be obtained.
Depending on your medical conditions, the type and dose of medication may be tailored to ensure you have an optimal colonoscopy. The preparation time before colonoscopy takes at least 4 hours. Therefore it is possible to perform colonoscopy on the same day if the medication is taken early in the morning. However, most patients prefer to take the medication at home and have the colonoscopy performed the enxt morning. Our clinic staff will explain clearly to you about the diet restrictions before the colonoscopy and how you drink the medication to ensure a comfortable preparation for the colonoscopy. A written copy of the instructions will also be provided to help you.
The Colonoscopy Procedure
Colonoscopy is done with you lying on your left side. An injection of a sedative and painkiller is usually given to make you relaxed and go into a light sleep. Your pulse and oxygen will be monitored throughout the examination to ensure your safety. The lubricated colonoscope is then gently introduced into the anus and steered through the entire large intestine. The entire procedure takes between 15 to 30 minutes excluding preparation time. In some cases, it may be necessary to take a sample of tissue (biopsy) for examination. When polyps are encountered, the doctor will remove them for examination.
Risks of Colonoscopy
As colonoscopy only involves pushing a tube through the colon without making any cuts, the risks are very small for any problems. Care will be taken to minimize discomfort but patients may feel mild cramping, bloating or gas after the procedure which can last up to 24 hrs. Heavy bleeding may occur after removal of a polyp and sometimes require transfusion but rarely requires reinsertion of colonoscope to control the bleeding. The risk of heavy bleeding is less than 0.1%. There is a slight risk of bowel perforation (tearing a hole) and the risk is increased in patients with multiple previous abdominal operations that may have caused adhesions and scarring in the abdomen. The overall risk of perforation is less than 1 in 1,000 or 0.1%.
What can I expect after a Colonoscopy?
After the procedure, you will be brought to the recovery area for monitoring and observation. You should not drive or operate machinery on the same day. For this reason, someone must be available to accompany you home. Your doctor will make an appointment to let you know the findings of the colonoscopy, answer any questions you may have, and if needed, discuss future treatment.
Alternatives to Colonoscopy
Alternative tests to colonoscopy include a barium enema or a CT colonography. Both are specialised forms of radiologic examination that outline the colon and allow a diagnosis to be made. CT colonography is commonly referred to as “virtual colonoscopy”. It involves performing the CT scan of a patient’s abdomen in prone (lying face down) and supine (lying face up) positions. The radiologist then uses a computer software to reconstruct the images into a 3D mode to simulate a colonoscope passing through the colon. However, the radiologist cannot take biopsies of the tumour to confirm cancer in these cases. Barium enema is an x-ray based test where a liquid contrast (barium) is inserted through the anus followed by filling the colon with air. Numerous x-rays are taken of the abdomen as the barium flows into the colon but this test is known to miss smaller cancers and biopsies cannot be taken either.
Study of the stools and blood can also provide indirect information about a colon condition. These exams, however, do not allow direct viewing of the colon, removal of polyps, or tissue samples of abnormal findings. Hence, these tests are only employed when a colonoscopy fails or when patients refuse to undergo colonoscopy.
If you have feedback or would like to know more about treatment for these conditions, feel free to contact us or make an appointment.