The main purpose of the study is to determine risk factors of poor bowel cleansing in inpatients after a split-dose high volume preparation with 4 liters of polyethylene glycol. The quality of colon cleansing will be measured by the Boston bowel cleansing scale (more than or equal to 2 points in each segment). The secondary aim is to design a predictive score of poor bowel cleansing.

It is well-known that inpatient status is a risk factor of inadequate bowel preparation. However this is a very mixed group, coexisting multiple factors containing several risk factors, such as elderly, comorbidities, a variety of medications, physical inactivity… Predictive factors in this population are probably different to those identified in outpatients. There is no strong evidence about the influence of these factors on inpatient bowel cleansing.

The researchers will offer to participate in the study to inpatients scheduled for 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 on the diet and the bowel cleansing solution to be taken. A questionnaire will be administered about predictors of inadequate bowel cleansing. Activity will be measured by using a pedometer and a physical performance test.

Patients will take a liquid diet the day before the examination and they will be prepared with 4 liters of polyethylene glycol in split-dose regimen: 2 liters the evening before the examination (at 19.00 hours) and 2 liters 5 hours before colonoscopy The bowel cleansing quality following Boston Bowel Preparation Scale will be assessed by the endoscopist during the colonoscopy.

The aim of this study is to figure out the risk factors of bowel cleansing of inadequate bowel preparation in inpatients.

The inclusion of a maximum of 10 variables in the multivariate analysis will be considered: age, sex, short test of physical performance, Charlson index, indication (urgent or scheduled), polymedication (≥ 5 drugs), exposure to tricyclic antidepressants, calcium antagonists or opioids, constipation (<3 deposits per week and one of the following defecatory efforts), number of steps. For a predetermined percentage of 25% of patients with inadequate preparation, the inclusion of 400 inpatients who undergo a colonoscopy will be required. If we estimate an inclusion of about 10 patients per week, an inclusion period of about 10 months would be required.

Inclusion Criteria:

• Inpatients with an indication of a colonoscopy
• Age ≥ 18 years.

Exclusion Criteria:

• Patients with previous colon surgery
• Last colonoscopy with poor bowel preparation.
• Ileus, intestinal obstruction, megacolon.
• Poorly controlled hypertension (Systolic and diastolic blood pressure > 180 and > 100, respectively).
• Terminal renal failure (pre-dialysis or dialysis).
• Congestive heart failure (NYHA III-IV).
• Acute liver failure.
• Severe psychiatric illness.
• Pregnancy or breastfeeding.
• Refusal to participate in the study.

The researchers will offer to participate in the study to inpatients scheduled for 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 on the diet and the bowel cleansing solution to be taken. A questionnaire will be administered about predictors of inadequate bowel cleansing. Activity will be measured by using a pedometer and a physical performance test.

Patients will take a liquid diet the day before the examination and they will be prepared with 4 liters of polyethylene glycol in split-dose regimen: 2 liters the evening before the examination (at 19.00 hours) and 2 liters 5 hours before colonoscopy