The goal of this clinical trial it is to bowel the instestinal preparation with lactulose vs poliethylenglicol as better agent to have a quality colonoscopy and demostrate that lactulose is most efective, has a good tolerance and the patient would have a better satisfaction, so the question is:

wich is the eficancy of lactulose in comparision with thepoliethylenglycol in the intestinal preparation for the colonoscopy?

A bowel preparation is fundamental before making a colonoscopy, letting us realize a correct exploration in all the bowel. The main method of cleaning would be fast, safe and getting a high grade of visualizing to do a quality colonoscopy.

Actually there are a lot of methods or products of cleaning the bowel. A good cleaning have a lot of successful choosing a good product to do it and having a good diet before the colonoscopy.

There are a lot of scales about the cleaning in the colonoscopy, having a good bowel preparation increase the capacity of the detection of polyps, decrease the time of the colonoscopy and getting better the cost and efficiency.

The colonoscopy plays a crucial role in the screening and treatment of colorectal cancer. It is an optimal procedure to identify precancerous lesions. polyps and recommended for screening people with risk factors, such as a family history of polyps or cancer.

Bowel preparation is a crucial aspect in colonoscopy due to its direct relationship with the quality of the procedure. Many patients find bowel preparation to be the most uncomfortable part of the examination, so ensuring that it is safe, extremely efficient, reliable, convenient and tolerable enough to ensure that patients will not be able to complete it or wish to undergo future procedures, associating this with the bad taste of the agents used and the adverse events produced.

Ignorance of the importance of adequate bowel preparation and cleansing explains poor adherence to instructions, and increases the rate of inadequate bowel preparation.

The health team must provide correct and clear information that improves patient adherence. The importance of compliance with the indications and the impact of adequate intestinal cleansing on the findings and results of colonoscopy should be emphasized.

The cleaning systems used in colonoscopy must allow more than 90% of the mucosal surface to be explored. Furthermore, the drugs used must be well tolerated by the patient and not cause side effects. Therefore, the ideal colonoscopy preparation should combine efficacy, excellent tolerance, and minimal adverse effects.

The use of oral bowel preparations may induce strong peristalsis, cramps, bloating, diarrhea and other symptoms. Intolerance to the preparation is common and is usually associated with the volume of liquid consumed and the taste of the solution.

Polyethyleneglycol (Muvinlax(r) or Nulytely is a non-absorbable electrolyte solution and does not induce electrolyte mucus secretion or significantly reduce fluid exchange in the colonic lumen. It has been shown to be non-toxic and can be ingested in large quantities without dangerous effects. Its use is relatively safe in patients with kidney failure, cirrhosis or congestive heart failure.

Bowel preparation with polyethyleneglycol represents the most used formula in our environment. Among the recognized limitations associated with its application are: the large amount of volume to be ingested (4 L), which makes it impossible to administer it to elderly people with swallowing difficulties, it is also poorly tolerated by patients and has been associated with medical complications, among which can be mentioned: vomiting, abdominal distension, abdominal pain, nausea, Mallory Weiss syndrome, esophageal perforation, bronchoaspiration, toxic colitis, pancreatitis induced by polyethyleneglycol.

Lactulose (Duphalac (r)) is a disaccharide, semi-synthetic derivative of lactulose. It is absorbed and undergoes bacterial action, which causes fermentation, acidifying the environment and causing acceleration of intestinal transit, stimulating motility. Another consequence of acidification is the increase in osmotic pressure within the lumen of the colon, proportional to the dose. Regarding the dose, 120 ml are diluted with juice or clear water until completing 1000 ml, swallowing the entire volume in 1 hour The preparation regimen has a significant impact on the quality of intestinal cleansing. Traditionally, preparation is done one day before a colonoscopy.

• Inclusion Criteria:
• Patients with indication for colonoscopy in our coloproctology service
• Both women and men
• Patients within an age range of 18-79 years
• Patients who agree having a colonoscopy and who sign the informed consent to participate in the protocol

Exclusion Criteria:

• Patients under 18 or over 80 years old
• All patients that won´t like to participate in the protocol or won´t sign the informed consent
• Pregnant women
• Patients with a medical record of colonic resection, ostomy status, severe cardiopulmonary and renal diseases, major psychiatric disorders, therapeutic colonoscopy or any contraindications for colonoscopy
• Non compliance with the colonic preparation regimen
• Active bleeding during the procedure
• Patients with a known diagnosis of colorectal cancer

The main investigators will be in charge of randomizing all the patients ellegible for this protocol, and the care providers and endoscopists will be masked when it comes to knowing to which arm of the study each patient belongs to, untill the moment they need to perform the colonoscopy.