What is a colonoscopy?

Colonoscopy is to insert an endoscopy from anus to cecum and to directly observe the large intestine and rectal mucosa. Tumor lesions or polyps discovered during a colonoscopy will be excised or a biopsy will be performed to achieve the purposes of diagnosis and treatment. Besides that, the other lesion in the colon will be identified.


Pre-colonoscopy preparations:

  1. The physician will explain the purpose and process of the colonoscopy, and ask you to fill in the informed consent form for colonoscopy and treatment.
  2. Follow a low-fiber diet two days before the colonoscopy, such as white toast, porridge, white noodles, cellophane noodles, minced pork floss or minced meat, etc. Avoid eating stalked vegetables (cauliflower, water spinach, celery), seed-containing fruits (guava, kiwi, Dragon fruit), grains and nuts, and dairy products (milk, goat's milk, cheese, yogurt).
  3. Follow a slag-free diet the day before the colonoscopy, such as sports drinks, rice soup, chicken essence, clear soup, tea, honey water, slag-free fruit juice (apple juice, wax guard tea), etc.; do not drink soy milk, milk, Ensure, or other fiber-containing food.
  4. After noon on the day before the colonoscopy, start taking a laxative according to the physician's instructions.  According to the type of laxative, it is necessary to take the laxative with more than 2000 CC of water.
  5. If the stool is not completely cleared after drinking the laxative, take the laxative again according to the physician’s orders. The colonoscopy cannot be accurate unless there is clean bowel preparation.
  6. On the day of the colonoscopy, patients who will receive general colonscopy can still take slag-free diet. Those who will receive painless colonoscopy cannot eat any food, drink water, or take medicine for at least four hours before the procedure.
  7. Patients may keep taking blood pressure lowering drugs and heart medications as usual. However, for diabetes patients, blood sugar lowering drugs should be suspended on the day of colonscopy. After colonscopy is completed, diabetes patients may take blood sugar lowering drug again after finish a meal. 


Colonoscopy Process:

  1. Take a horizontal position with the knee bent on the left side during the colonoscopy.
  2. After the endoscope is inserted into the anus, a small amount of air will be injected to assist the physician for the orientation of endoscope.
  3. When the endoscope reaches the sigmoid colon, the patient will be helped to change the posture to a supine position for endoscope passing through the curve of the right colon.
  4. The colonoscopy does not require anesthesia. However, if you are nervous about the examination, suffer from intestinal adhesion, have excessive intestinal curvature, or any difficulty in examination, you can be assessed by an anesthesiologist for a painless colonoscopy at your own expense to reduce the level of discomfort. However, during painless colonoscopy, you must be accompanied by a family member.
  5. If you experience any discomfort during the colonoscopy, please take the initiative to inform medical staff on site.


Post-colonoscopy Preparations:

  1. The nurse will pay attention to the changes in your blood pressure, pulse, breathing, and body temperature.
  2. After the colonoscopy, you may experience mild abdominal distension and abdominal discomfort. You can turn over and move more to help pass gas and reduce the discomfort. If you experience severe abdominal pain or bleeding, please inform the healthcare personnel immediately.
  3. After the colonoscopy, on the same day, you can resume your normal diet. If you underwent a biopsy or polypectomy during the colonoscopy, follow a low-fiber or slag-free diet as instructed by your physician. Gradually increase your fiber intake the next day. Avoid eating fried and spicy foods because irritation of the intestines may lead to inflammation or bleeding in the sliced wound.
  4. Due to safety concerns, those undergoing painless colonoscopy should not drive or engage in any work requiring concentration on the day of colonoscopy.


  1. Chang, C. W., Kao, S. L., Wang, S. H. (2017). Analysis of using standard processes for upgrading colonoscopy patients' intestinal cleanliness in health examination center. Changhua Nursing, 24(1), 33-40. https://doi.org/10.6647/CN.24.01.12
  2. Hashash, J. G., El-Haddad, A., & Barada, K. (2018). Acute epigastric abdominal pain post-gastric polypectomy. Gastroenterology, 154(4), e12-e14. https://doi.org/10.1053/j.gastro.2017.05.061
  3. Kastenberg, D., Bertiger, G., & Brogadir, S. (2018). Bowel preparation quality scales for colonoscopy. World Journal of Gastroenterology, 24(26), 2833-2844. https://doi.org/10.3748/wjg.v24.i26.2833
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