The success of colonoscopy is closely related to the quality of colonic preparation. However, data regarding colonoscopy preparations in the elderly (65 years older) are scarce. Split-dosage cathartic bowel preparation are currently suggested, whereas supporting evidence is lacking in this particular group of patients. Moreover, patient tolerability is a key factor for success of bowel preparation in the aged people.

The purpose of this study is to compare the bowel cleansing efficacy and patient compliance of following bowel preparation methods prior to elective outpatient colonoscopy in the elderly: (1) standard preparation of 4 liters (L) PEG-3350 solution on the night before colonoscopy, (2) split-dose of 4L PEG-3350 solution, and (3) split-dose of reduced volume [2L] PEG-3350 containing ascorbic acid solution.

Inclusion Criteria:

• elderly people aged over 65 years
• elective outpatient colonoscopy
• informed consent

Exclusion Criteria:

• patients who had bowel movements of less than 3 per week during last one month
• patients who have a history of renal dysfunction (abnormal elevation of serum creatinine and electrolyte imbalance)
• patients who have a history of alimentary tract surgery
• patients who have other gastrointestinal diseases that are not suitable for undergoing colonoscopy (gastroparesis, gastric outlet obstruction, ileus, ischemic colitis, megacolon, and toxic colitis)
• patients classified as the American Society for Anesthesiology class III or higher
• Any condition which, in the opinion of the Investigator, places the patient at unacceptable risk if he/she were to participate in the study