The purpose of this study is to compare two regimens of low volume (2L) polyethylene glycol(PEG)plus ascorbic acid versus standard volume (4L) PEG alone for bowel preparation in out-patients

Inadequate bowel preparation may lead to a longer colonoscopy, and to an inability to identify lesions. PEG can provide a rapid orthograde peroral approach to colonic lavage without producing significant fluid or electrolyte changes. Thus PEG is now commonly used for bowel preparation. However, large amounts and unsatisfactory taste of PEG solution are generally poorly tolerated. a new low volume PEG-based bowel cleansing agents became available at foreign countries. Although several studies reported the efficacy and improved compliance of these low volume PEG plus ascorbic acid solution for colonoscopy, but result in Korean patients was not-recognized.

Inclusion Criteria:

• Out-patients for colonoscopy

Exclusion Criteria:

• age under 19 years or over 80 years
• Intestinal obstruction
• Women of pregnant, breastfeeding, or at risk of becoming pregnant
• major psychiatric illness
• known allergy to PEG
• serious condition- severe cardiac, renal, or metabolic diseases
• past history of colon resection
• current acute exacerbation of chronic inflammatory bowel disease
• functional constipation defined by Rome III diagnostic criteria

Out-patients for colonoscopy in university hospital