An adequate level of bowel preparation before colonoscopy has an extremely relevant impact on lesion detection and procedure success. The inpatient status represents a well-known independent predictor for inadequate colon cleansing. A recent prospective, multicentre, Italian study among inpatients showed that an adequate colon cleansing was achieved in 60-70% of patients, far below the ideal threshold of 90%. Interestingly, a higher rate of adequate colon cleansing was reported for a very low-volume (1L) polyethylene glycol (PEG)-based preparation when compared to 4L and 2L PEG-based solutions. However, this finding has to be confirmed as the study was not controlled and the PEG-1L group was much smaller than the other two.

Aim of the present multicenter randomized controlled study will be to assess and compare the efficacy and safety of a novel very-low volume (1L) PEG-based preparation vs. standard-of-care low-volume (2L) and high-volume (4L) PEG-based purge, among inpatients who undergo colonoscopy.

An adequate level of bowel preparation before colonoscopy has an extremely relevant impact on lesion detection and procedure success. The inpatient status represents a well-known independent predictor for inadequate colon cleansing. A recent prospective, multicentre, Italian study among inpatients showed that an adequate colon cleansing was achieved in 60-70% of patients, far below the ideal threshold of 90%. Such a low efficacy has several negative consequences: first, it leads to repetition of colonoscopy, therefore prolonging patients' in-hospital stay and increasing the risk of adverse events and costs; second, it augments the risk of missing colorectal lesions, negatively affecting patients' management and increasing costs due to the need for adjunctive diagnostic studies.

Current recommendations on bowel preparation among difficult-to-prepare patients are mostly based on expert opinions, the high-volume 4L polyethylene glycol (PEG)-based prep being considered as the gold standard, possibly with further additional solution. On the other hand, compliance to the bowel preparation has been related to an adequate colon cleansing, and it may be argued that inpatients might find it difficult to take high-volume purge. A recent Italian prospective multicentre study among inpatients showed similar rates of adequate bowel preparation between patients who underwent bowel preparation with and without additional solution. Interestingly, a higher rate of adequate colon cleansing was reported for a very low-volume (1L) polyethylene glycol (PEG)-based preparation when compared to 4L and 2L PEG-based solutions. However, this finding has to be confirmed as the study was not controlled and the PEG-1L group was much smaller than the other two.

Aim of the present randomized multicenter controlled study will be to assess and compare the efficacy and safety of a novel very-low volume (1L) PEG-based preparation vs. standard-of-care low-volume (2L) and high-volume (4L) PEG-based purge, among inpatients.

Inclusion Criteria:

• Inpatients scheduled for elective colonoscopy
• bowel preparation performed inside the hospital
• ≥18 years old

Exclusion Criteria:

• known or suspected ileus
• gastrointestinal obstruction
• gastric retention
• bowel perforation
• toxic colitis, or megacolon
• phenylketonuria
• glucose-6-phosphate dehydrogenase deficiency
• active intestinal bleeding
• emergency colonoscopy
• dementia or illness requiring nasogastric tube for bowel prep administration
• refusal to participate or inability to sign the informed consent