Colon Cleansing Quality of Polyethylene Glycol Compared With Polyethylene Glycol Plus Ascorbic Acid.

\- Polyethylene glycol 4000: 16 envelopes (70 g of powder each). It includes electrolytes and sodium sulfate. These substances make PEG metabolically inert, achieving a suitable osmotic balance, despite having a high molecular weight. The preparation passes along the gastrointestinal tract without causing net absorption of fluid or electrolytes. It is routinely used in clinical practice for bowel cleansing, before abdominal surgery, barium enema and other colorectal and genitourinary tract tests. Participants will divide the whole doses in 4 liters of water taking half the day before the examination starting at 20.00 h and the other half at 6.00 pm on the day of the examination.

\- Macrogol 3350 plus ascorbic acid: 4 envelopes, 2 containing 112 g polyethylene glycol and electrolytes and 2 with 2 g of ascorbic acid. The properties of the polyethylene glycol are the same as those mentioned previously, while ascorbic acid generates an osmotic gradient potentiating the effect of polyethylene glycol. It is used routinely as a bowel prep. Participants will divide the doses in 2 liters of water taking half the day before (112 g of PEG and an 11 g of ascorbic acid) the examination at 20.00 h and the other half at 6.00 pm on the day of the examination