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A colonoscopy can only find polyps and early cancers if the bowel is clean. Eat low-fibre food the day before, drink the laxative in two halves (the evening before and the morning of the test, or all on the day for an afternoon test), and finish the last dose at least two hours before the test. Follow your unit's written instructions, which come first.
ESGE 2019 (GRADE): a low-fibre diet on the day before (strong, moderate); enhanced instructions, verbal or written, for patients and for ward staff caring for inpatients (strong, moderate); split-dose preparation for elective colonoscopy (strong, high), with same-day dosing an acceptable alternative for afternoon lists (strong, high); start the last dose within 5 hours of the procedure and finish it at least 2 hours before (strong, moderate); high- or low-volume PEG or clinically validated non-PEG agents, individualised where fluid and electrolyte disturbance is a risk (strong, moderate); simethicone suggested (weak, moderate); no routine enemas (strong, moderate), no routine oral sodium phosphate (strong, low) and no routine prokinetics (weak, low). After an inadequate preparation, repeat within a year (strong, moderate). PEG in inflammatory bowel disease and urgent bleeding; insufficient evidence in pregnancy. The US Multi-Society Task Force (2025) agrees on split dosing (and suggests 2 litres may be enough), same-day dosing for afternoon procedures (an inferior alternative in the morning), restriction limited to the day before with clear liquids or low-fibre food for early meals, and simethicone, and sets a target of more than 90% adequate preparations per endoscopist and per unit; ESGE's quality committee sets a minimum standard of 90% or more, assessed on validated scales.
Why: Most poor preparations come from instructions that were unclear or not followed.
“ESGE recommends specific verbal or written instructions to patients and to clinic staff caring for hospitalized patients, to improve the quality of bowel preparation.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, moderate quality evidence.
Why: Some laxatives shift fluid and salts, which matters most for weak kidneys or hearts.
“ESGE recommends the use of high volume or low volume PEG-based regimens as well as that of non-PEG-based agents that have been clinically validated for routine bowel preparation. In patients at risk for hydroelectrolyte disturbances, the choice of laxative should be individualized.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, moderate quality evidence.
Why: It can damage the kidneys and upset blood salts.
“ESGE recommends against the routine use of oral sodium phosphate for bowel preparation.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, low quality evidence.
Why: Less fibre leaves less residue in the bowel to hide the lining.
“ESGE recommends a low fiber diet on the day preceding colonoscopy.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, moderate quality evidence.
Why: Splitting the dose cleans the bowel better than taking it all the day before.
“ESGE recommends split-dose bowel preparation for elective colonoscopy.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, high quality evidence.
Why: Same-day dosing works as well for afternoon lists and avoids an evening dose.
“ESGE recommends, for patients undergoing afternoon colonoscopy, a same-day bowel preparation as an acceptable alternative to split dosing.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, high quality evidence.
Why: The bowel is cleanest a few hours after the last dose; finishing 2 hours before keeps the stomach empty for sedation.
“ESGE recommends to start the last dose of bowel preparation within 5 hours of colonoscopy, and to complete it at least 2 hours before the beginning of the procedure.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, moderate quality evidence.
Why: It reduces bubbles that can hide small polyps.
“ESGE suggests adding oral simethicone to bowel preparation.”
ESGE (Hassan et al., Endoscopy) 2019 · Weak recommendation, moderate quality evidence.
Why: In trials, adding an enema did not clean the bowel better and made preparation harder to bear.
“ESGE recommends against the routine use of enemas for bowel preparation.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, moderate quality evidence.
Why: A poorly prepared bowel can hide polyps and cancers, so the examination needs doing again.
“ESGE recommends early repetition of colonoscopy within 1 year in the case of inadequate bowel preparation, unless clinically contraindicated.”
ESGE (Hassan et al., Endoscopy) 2019 · Strong recommendation, moderate level of evidence.
How care is usually carried out, read from the guidelines and standards cited. Your own team's protocol and their judgement come first; this page is for understanding it, not for doing it yourself.
Split-dose preparation (ESGE strong, high quality; US Multi-Society Task Force 2025 recommends), or same-day dosing for afternoon procedures; the last dose started within 5 hours and finished at least 2 hours before; a validated PEG or non-PEG laxative chosen individually for people at risk of fluid and salt disturbance, without routine oral sodium phosphate, enemas or prokinetics; low-fibre food on the day before only; enhanced instructions; simethicone suggested. The two guidelines differ in emphasis: the US Task Force allows clear liquids or low-fibre food for early meals on the day before, suggests a 2-litre regimen may be sufficient, and calls same-day dosing an inferior alternative for morning procedures, where ESGE addresses same-day dosing only for afternoon lists.
ESGE (Hassan et al., Endoscopy) 2019 · US Multi-Society Task Force on Colorectal Cancer (Jacobson et al., Gastroenterology) 2025
Where it differs: Restricts the person to clear liquids for the whole day before, rather than low-fibre food.
Evidence: ESGE recommends a low-fibre diet and notes that adherence to diet restriction is low in real life; the US Task Force (2025) allows either clear liquids or a low-fibre or low-residue diet for the early and midday meals of the day before.
ESGE (Hassan et al., Endoscopy) 2019 · US Multi-Society Task Force on Colorectal Cancer (Jacobson et al., Gastroenterology) 2025
Where it differs: Uses a lower-volume PEG with ascorbate, or a non-PEG agent such as sodium picosulfate with magnesium citrate or oral sulfate solution, instead of 4 litres of PEG.
Evidence: ESGE accepts both high- and low-volume PEG and validated non-PEG agents (strong, moderate) and individualises the choice where fluid and salt disturbance is a risk; the US Task Force suggests a 2-litre regimen may be sufficient. The relative safety of each agent in kidney or heart failure was not read in full here.
ESGE (Hassan et al., Endoscopy) 2019 · US Multi-Society Task Force on Colorectal Cancer (Jacobson et al., Gastroenterology) 2025
| Recommendation | Grade, as printed | Source |
|---|---|---|
| Enhanced instructions for bowel preparation “ESGE recommends the use of enhanced instructions for bowel preparation.” | Strong recommendation, moderate quality evidence. | ESGE (Hassan et al., Endoscopy) 2019 |
| PEG regimens in inflammatory bowel disease “ESGE recommends high volume or low volume PEG-based bowel preparation in patients with inflammatory bowel disease (IBD).” | Strong recommendation, high quality evidence. | ESGE (Hassan et al., Endoscopy) 2019 |
| PEG regimens for urgent colonoscopy for lower gastrointestinal bleeding “ESGE recommends PEG regimens for bowel preparation if urgent colonoscopy is scheduled for lower gastrointestinal bleeding (LGIB).” | Strong recommendation, moderate quality evidence. | ESGE (Hassan et al., Endoscopy) 2019 |
| No routine prokinetic agents “ESGE does not suggest the routine use of prokinetic agents for bowel preparation.” | Weak recommendation, low quality evidence. | ESGE (Hassan et al., Endoscopy) 2019 |
| Pregnancy and breastfeeding: insufficient evidence for a specific regimen “ESGE found insufficient evidence to determine for or against the use of specific regimens in pregnant/breastfeeding women.” | Insufficient evidence to determine net benefits or risks. | ESGE (Hassan et al., Endoscopy) 2019 |
| Split dosing recommended; same-day an inferior alternative for morning colonoscopy (US) “We recommend the use of a split-dose bowel preparation regimen and suggest that a 2 L regimen may be sufficient.” | recommend / suggest (GRADE terms in abstract; full grades not read) | US Multi-Society Task Force on Colorectal Cancer (Jacobson et al., Gastroenterology) 2025 |
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