Factors influencing quality of bowel preparation for colonoscopy

Table 1 Summary of American Society for Gastrointestinal Endoscopy, American Society of Colon and Rectal Surgeons, Society of American Gastrointestinal and Endoscopic Surgeons consensus recommendations on colon cleansing agents for bowel preparation during colonoscopy

Agent	Dosing	Recommendation	Level of evidence
PEG	240 mL every 10 min until rectal output is clear or total of 4 L	Faster, more effective, better-tolerated compared to dietary restriction with cathartics, gut lavage, or mannitol	Grade IA
Sulfate-free PEG	240 mL every 10 min until rectal output is clear or total of 4 L	Better tasting, comparable to PEG in effectiveness and safety, acceptable alternative to PEG	Grade IIB
Low-volume PEG/PEG-3350 and bisacodyl	4 bisacodyl delayed-release tablets at noon, after bowel movement or 6 h, 240 mL every 10 min until 2 L is consumed	Equally effective to standard 4-L PEG, better tolerated, acceptable alternative to 4-L PEG	Grade IA
Aqueous sodium phosphate	Two doses of 30 to 45 mL sodium phosphate with 8 oz of liquid 10-12 h apart	Equal alternative to PEG except for pediatric and elderly patients, bowel obstruction, renal failure, congestive heart and liver failure	Grade IA
Sodium phosphate tablets	20 tablets on the evening before the procedure, 12-20 tablets 3-5 h before the procedure	Improved taste and palatability compared to aqueous sodium phosphate, but no improvement in patient tolerance	Grade IA

PEG: Polyethylene glycol-electrolyte.

Table 2 Predictive factors for quality of bowel preparation independent of colon cleansing agent

Patient-related factors	Procedure-related factors
Age > 65 yr
Male gender	Adherence to bowel preparation instructions
Co-morbidity	Timing of purgative administration
Diabetes
Stroke disease
Inpatient status
Low socioeconomic status	Appointment waiting times