The primary aim of the study is to increase the success rate of cecal intubation in first colonoscopy and in repeated colonoscopy for the first failed procedure. The secondary aims are to assess the procedure time, the terminal ileum intubation rate, the endoscopist satisfaction score, the patients' acceptance, the complication rate of these two procedures, and the intravenous sedative drugs used.

Currently there is no consensus in how to improve the success rate of colonoscopy procedure given the fact that 10% of the procedures may fail. It has been suggested that using variable stiffness colonoscope (a colonoscope with a shaft that the stiffness can be altered), or even more sophisticated magnetic imaging colonoscopy (colonoscopy performed under a magnetic position detection sensor), could improve the success rate. However, these kinds of equipment are either expensive or not always available in the daily clinical practice. From some recent studies it was shown that adding a transparent cap to the tip of the colonoscope may improve the procedure success rate without increasing the complication rate of the procedure. The cost of the cap is cheap and it is available in almost every endoscopy center. Therefore the cap-assisted colonoscopy method may be an alternative which may improve the success rate of colonoscopy procedure, and reduce the pain and discomfort related to the procedure.

Inclusion Criteria:

• Patients who undergo their first colonoscopy examination

Exclusion Criteria:

• Patients had received colonoscopy examination before
• Patients had prior colorectal surgery done (apart from appendectomy)
• Known to have colonic stricture or obstructing tumor from the results of other investigations such as CT scan or barium enema
• Presence of acute surgical conditions such as severe colitis, megacolon, ischemic colitis and active gastrointestinal bleeding