【Learning Key Points】

1. Colonoscopy is an endoscopic procedure used to diagnose and evaluate diseases and abnormalities of the colon.
2. Before the examination, follow a low-residue diet, such as white bread, steamed buns, steamed eggs, and thin noodles.
3. Because air is introduced into the intestine during the examination, you may experience abdominal bloating, abdominal discomfort, or abdominal pain afterward. Changing your position or walking around may help relieve these symptoms.

I. What Is a Colonoscopy?

1. Colonoscopy is one of the endoscopic methods used to examine and diagnose abnormalities of the colon.
2. Procedure:
   The physician gently inserts a flexible colonoscope through the anus and advances it slowly through the rectum, sigmoid colon, descending colon, transverse colon, and ascending colon, eventually reaching the cecum when the bowel anatomy permits. If inflammation, polyps, tumors, bleeding, or other abnormalities are identified during the examination, further procedures may be performed, such as polypectomy, tissue biopsy, or electrocautery for hemostasis.

II. Preparation Before the Examination

1. Complete and sign the required procedure and anesthesia consent forms.
2. Follow a low-residue diet for two days before the examination.
3. On the day before the examination, consume only a clear liquid diet.
4. Patients undergoing sedated or painless colonoscopy should not eat or drink after midnight before the examination, unless otherwise instructed by the healthcare team.
5. Other regular medications:
   1. Blood glucose-lowering medications: Patients taking medications for diabetes should withhold these medications on the morning of the examination,  according to the physician's instructions.
   2. Antihypertensive medications:Blood pressure medications may generally be taken with a small amount of water, as instructed by the physician.
   3. Anticoagulants: Patients taking anticoagulant medications should discuss medication management with their prescribing physician in     advance before the examination.
6. Take the bowel preparation solution according to the physician's instructions.
   1. Niflec / GI Klean：
      1. For a morning examination, take the bowel preparation at 6:00 PM on the evening before the examination and at 4:00 AM on the morning of the examination.
      2. For an afternoon examination, take it at 6:00 AM and 10:00 AM on the day of the examination.
      3. How to take it:
         1. The solution is flavorless and comes in two bottles. Dilute the contents with 2,000 mL of cold water.
         2. Drink the first 1,000 mL, approximately 200 mL every 10 minutes.
         3. Drink the remaining 1,000 mL over the next 1–2 hours.
         4. d. You will usually begin to feel the urge to have a bowel movement approximately one hour after taking the bowel preparation.
         5. Observe the stool during bowel movements. When the stool becomes clear, transparent, and yellowish liquid, the bowel preparation is considered adequate.
   2. Bowklean
      1. Take one bottle at 6:00 PM on the evening before the examination and another bottle at 4:00 AM on the morning of the examination, as instructed.
      2. How to take it:
         1. The solution has a lemon flavor. There are two bottles. Dilute each bottle as instructed with approximately 2,000 mL of cold fluids, such as an electrolyte drink or bottled water.
         2. In addition, drink approximately 1,500 mL of water or an electrolyte drink to maintain adequate hydration.
         3. Nausea, vomiting, and abdominal bloating may occur after taking the bowel preparation. These can be expected side effects. If these symptoms occur, wait until they improve before continuing the bowel preparation, according to the healthcare team's instructions.
         4. You will generally begin to feel the urge to have a bowel movement approximately 30–60 minutes after taking the medication, and its effects may last approximately 2–4 hours.

III. Post-Colonoscopy Care

1. Abdominal bloating, abdominal pain, and passing gas (through flatulence or belching) may occur because air is introduced into the intestine during the colonoscopy. These symptoms usually improve within approximately 6 hours to 2 days. Changing position or walking around may help relieve the discomfort.
2. Approximately 2 hours after the examination, you may first try drinking water. If there is no nausea or vomiting, you may gradually resume eating. On the day of the examination, start with half portions and a soft diet. You may generally resume a regular diet the following day. Soft foods include congee, noodles, steamed buns, steamed eggs, and similar foods. Avoid hard or coarse vegetables and nuts.
3. If a colon polyp has been removed, follow a bland, soft diet for one week. Avoid pepper, chili, alcoholic beverages, and hard or acidic fruits during this period.

IV. Conclusion

1. After returning home, if you develop severe abdominal pain, passage of a large amount of bloody stool, fever, or other unusual symptoms, return to the emergency department immediately for medical evaluation.
2. If a colon polypectomy was performed, the physician will determine the appropriate timing for the next follow-up based on your clinical condition. Please return for follow-up at the time specified by your physician.

V. Reference

1. Lee, L., & Saltzman, J. R. (2026, February 11). Overview of colonoscopy in adults. In D. G. Adler (Ed.) & K. M. Robson (Dep. Ed.), UpToDate. UpToDate. Retrieved April 9, 2026, from https://www.uptodate.com/contents/overview-of-colonoscopy-in-adults