For effective cleansing of the bowel prior to colonoscopy polyethylene glycol (e.g. macrogol) has widely been used in Germany. Usually patients have to drink between 4 an 6 liter of macrogol in a split dose (3 liter on the day before and 1 to 3 liter on the of the examination). One handicap of using polyethylene glycol is the occurence of nausea and vomiting which is due to the high amount of the laxativ and its bad taste. Therefore in a pilot study the investigators have detected a high fraction of patients who consider the cleansing procedure wich macrogol as "very distressing". Thus patient acceptance of the colonoscopy procedure altogether is low.

Since a few month sodium picosulfate/magnesium citrate is available for bowel cleansing in Germany. This preparation tastes better and needs less fluid intake. Usually 150 ml of sodium picosulfate/magnesium citrate are given twice within a 12 hour interval. Patients are instructed to drink plenty of water in addition to the laxative. In the mentioned pilot study the investigators found the cleansing procedure with picosulfate/magnesium citrate to be much more compatible compared to the macrogol regime. The effectiveness expressed by the cleanness of the bowel was equal in both groups.

The investigators believe that a new protocol which contains sodium picosulfate/magnesium citrate instead of macrogol will benefit the patients by fewer abdominal side effects while cleanness of the bowel at the same time will be warranted. This presumption is the reason for the present study.

Inclusion Criteria:

• Age >= 18
• Scheduled for colonoscopy

Exclusion Criteria:

• No informed consent
• ASA IV or V
• Pregnancy