Colonoscopy examination

Why is Colonoscopy performed | Pre-operative Preparations | Procedures | Post-operative Instructions | Possible Risks and Complications

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 sigmond 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 haemostasis when necessary.

Why is Colonoscopy performed?

  • Blood in stool
  • Anemia
  • Change in the bowel habits
  • Chronic diarrhea
  • Unexplained abdominal pain
  • Colorectal polyps / tumors
  • Colon cancer screening

Bowel Preparation Video

Preparation before Exam

Bowel preparation can be carried out at home or in the hospital.

The day before colonoscopy, Only fluid diet is allowed, such as clear meat soup and thin congee. Please do not consume too much dairy products.
Two days before colonoscopy, The client can only consume low residue diet (avoid food which is rich in fiber, e.g. vegetable, fruit, cereal etc).

No oral intake is allowed six hours before colonoscopy.


Change into a surgical gown after removing all belongings.


Colonoscopy takes about 30 minutes

After Exam

Stay in bed until the sedative effect of drug has been completely worn off

Pre-operative Preparations

  • On the day of colonoscopy
    No food or drink six hours before colonoscopy.
  • Please change into a surgical gown after removing all clothing including undergarments, dentures, jewellery and contact lenses.


  • Patient has to lie on his left side with both knees bending towards his chest.
  • Doctor may prescribe sedation or anesthetic medication according to patient’s condition.
  • Doctor will pass the colonoscope through the anus into the colon. It is normal to feel mild abdominal distension and urging of bowel during the procedure.
  • The procedure usually takes about 30 minutes.

Post-operative Instructions

  • After colonoscopy, patient should stay in bed until the sedative effect of drug has been completely worn off. It usually takes 3 – 4 hours.
    For Out-patient
    For your safety, please arrange a responsible adult to stay with you when you leave the hospital. If there is no companion, recovery bed has to be arranged for you after the procedure (additional charge for observation will be levied).

Possible Risks and Complications

Before examination
   - Laxative for bowel preparation may cause nausea, vomiting, abdominal pain or distension, etc.
During examination
   - Injection of sedation may cause hypotension, respiratory difficulties. For severe cases, anaphylaxis and anaphylactic shock may be developed. The probability of developing such symptoms is higher for the elderly.
   - Perforation (2:1000); the probability of developing major complications is higher for those clients who need to have therapeutic procedure (e.g. polypectomy, endoscopic haemostasis, dilatation and insertion of stent).
   - Perforation of bowel leading to peritonitis. Laparotomy under general anaesthesia may be required or repair or resection of bowel. The death rate is 5 in 100.
After examination
   - May experience abdominal pain or distension etc. It will improve about one hour after examination.
   - Bleeding may occur after polypectomy (1:1000), which usually happens within 24 hours of examination