The main purpose of the study is to evaluate in a prospective cohort of patients with an appointment for the performance of an outpatient colonoscopy the prediction of the quality of colonic cleansing through the use of 3 predictive models.

The colon cleansing quality will be assessed by a validated scale (Boston Bowel Preparation Scale, BBPS). Patients will be prepared with polyethylene glycol (PEG), PEG plus ascorbic acid (PEG-Asc) or sodium picosulfate-oxide magnesium solution (PS).

Although, current guidelines recommend a rate of inadequate bowel cleansing for colonoscopy not higher than 10-15%, in clinical practice poor bowel cleansing in endoscopy units ranged between 6.8% and 33%. The determinants of poor cleanliness have been evaluated in different studies and can be classified into patient-dependent predictors, which include demographic, socioeconomic and clinical variables, variables dependent on the preparation protocol, including the assigned diet, the type of preparation, its fractionation and the space of time elapsed between the last intake and the colonoscopy, and the tolerance mainly attributed to the volume and taste of the evacuating preparation The American Association of Gastrointestinal Endoscopy recommends the administration of additional preparation to these patients with a higher probability of inadequate preparation. Once non-compliance and lack of tolerance to cleaning protocols are excluded, the reason for inadequate preparation is usually the lack of effectiveness of the cleaning protocol. Therefore, it is advisable to select patients who can benefit from supplemented cleaning preparation or intensified cleaning protocols.

There are so far 4 published predictive models that incorporate clinical variables with the aim of determining patients who are candidates for intensified preparations. Of the models mentioned in the previous studies, only 3 are clearly detailed in the corresponding articles.

The researchers will offer to participate in the study to patients scheduled for a colonoscopy who meet all the inclusion criteria and none of the exclusion criteria. The researchers will explain the purpose of the study and will ask to sign the informed consent. They will give verbal and written information.

Subsequently, the colonoscopy will be performed and the cleaning quality will be scored according to the BBPS considering suboptimal a cleaning quality of less than 2 points in a segment of the colon.

The bowel cleansing quality following BBPS will be assessed by the endoscopist

Inclusion Criteria:

• Age >18
• To sign the informed consent,
• Patients with indication of outpatient colonoscopy
• Patients ingesting preparation

Exclusion Criteria:

• Resection of more than one colon segment.
• Ileus, intestinal obstruction, megacolon.
• Poorly controlled hypertension (HTAS> 180 HTAD> 100).
• Terminal renal failure (pre-dialysis or dialysis).
• Congestive heart failure (NYHA III-IV).
• Acute liver failure.
• Severe psychiatric illness.
• Dementia with difficulty in the intake of the preparation.
• Pregnancy or breastfeeding.
• Refusal to participate in the study.
• Allergies.
• Incomplete colonoscopy except for poor bowel cleansing

The researchers will offer to participate in the study to outpatients scheduled for a colonoscopy who meet all the inclusion criteria and none of the exclusion criteria. The researchers will explain the purpose of the study and will ask to sign the informed consent. They will give verbal and written information.

Data will no be available to other researchers