Comparison of reduced volume versus four-liter electrolyte lavage solutions for colon cleansing. 
In an attempt to improve patient tolerance for colon cleaning, a reduced-volume regimen with a 2-liter electrolyte lavage solution plus 20 mg of oral bisacodyl was compared with the standard 4-liter lavage for efficacy and safety.  Three hundred patients were prospectively randomized into two study groups.  One group of 150 patients was given four tablets of 5 mg bisacodyl at 12:00 PM the day before their colonoscopy, followed by 2 liters of electrolyte lavage by mouth at 6:00 PM the evening before their colonoscopy.  Another group of 150 patients were given 4 liters of electrolyte lavage at 6:00 PM the evening before their colonoscopy.  All patients were on a clear liquid diet the day before their colonoscopy.  No enema was given in either groups.  The bowel cleanliness was accessed by one colonoscopist.  One registered nurse accessed the comfort of patient.  In the 2-liter group, only one (0.6%) patient could not finish the laxative.  Colon cleanliness was 80 per cent to 100 per cent, with an average of 95.9 per cent.  In the 4-liter group, 11 (7.3%) patients could not finish the laxative preparation.  Colon cleanliness was 78 per cent to 100 per cent, with an average of 95.3 per cent.  The study that found the 2-liter electrolyte lavage solution with four tablets of bisacodyl can achieve equally good results in bowel preparation and favorable acceptance by patients compared with the 4-liter lavage.