Patients were randomly assigned to one of two groups : group I ( one-day schedule , n = 20 ) received a fiber-free diet and 3 L of polyethylene glycol ( PEG ) on day 0 ; group II ( two-day schedule , n = 20 ) received a liquid diet and 3 L of PEG in the evening of day -1 , and 1L of PEG in the early morning of day 0 .