Bowel preparation can be a troublesome procedure for patients undergoing colonoscopy. For patients with cardio-vascular and kidney disorders it may be dangerous with traditional bowel preparation with regard to salt and electrolyte balance. This study's purpose is to find out if nutritional drinks can replace traditional bowel preparation before colonoscopy in regard to Bowel purity degree, disturbances in the salt and electrolyte balance in the nutritional group versus the group that gets traditional bowel preparation. And if the patients tolerate nutritional drinks better than traditional bowel preparation.