Administration of olive oil followed by a low volume of polyethylene glycol-electrolyte lavage solution improves patient satisfaction with right-side colonic cleansing over administration of the conventional volume of polyethylene glycol-electrolyte lavage solution for colonoscopy preparation

Gastrointest Endosc. 2009 Sep;70(3):515-21. doi: 10.1016/j.gie.2009.01.002. Epub 2009 Jun 24.


Background: Proper bowel cleansing before colonoscopy is essential for satisfactory evaluation of the colon. The required consumption of a large volume of salty-tasting liquid, 4 L of polyethylene glycol-electrolyte lavage solution (PEG-ELS), is the primary limitation to achieving this goal.

Objective: To achieve better patient satisfaction with efficient bowel cleansing, we compared the effects of the conventional volume (4 L) of PEG-ELS with those of a low volume (2 L) in combination with pretreatment using different laxatives, such as magnesium hydroxide (milk of magnesia) and olive oil.

Design: Randomized, controlled study.

Setting: A single research hospital.

Patients: Patients undergoing elective colonoscopy.

Interventions: A total of 120 patients were randomized to 1 of 3 different preparation regimens: 39 patients were prepared with a conventional volume (4 L) of PEG-ELS (Preparation [Prep] 1), and the remaining patients were prepared with a lower volume (2 L) of PEG-ELS and pretreatment with a laxative, either 15 g of magnesium hydroxide (40 patients, Prep 2) or 60 mL of olive oil (41 patients, Prep 3) 3 hours before PEG-ELS administration.

Main outcome measurements: The primary outcome was the efficacy of colonic cleansing on the left and right sides. Secondary outcomes were patient satisfaction and side effects.

Results: The olive oil regimen (Prep 3) resulted in significantly more adequate bowel cleansing of the right colon than administration of the conventional volume of PEG-ELS (Prep 1) and the magnesium hydroxide (Prep 2) regimen (97.6% vs 74.5% and 72.5%, respectively, P = .007). However, this difference was not observed in the left colon (91.5%, 85.5%, and 91.8% for Preps 1, 2, and 3, respectively, P = .776). When asked, 38 patients (95%) taking Prep 2, 35 patients (85.3%) taking Prep 3, and only 11 patients (28.2%) taking Prep 1 preferred the same preparation regimen if they required a future colonoscopy (P =.006), based on ease of use and taste. The side effects were comparable in each group.

Limitations: The limitations of this study include the relatively small sample size, the single-center study design, and the use of a nonvalidated symptom scoring system.

Conclusion: Pretreatment with olive oil before administration of a low volume of PEG-ELS enhances both patient satisfaction and the quality of right-side colonic cleansing over the administration of the conventional volume of PEG-ELS for colonoscopy preparation. Although the magnesium hydroxide regimen (Prep 2) was the preferred regimen in this study, its colonic cleansing effectiveness was not as great as those of the other regimens. Based on our results, the olive oil regimen is recommended, especially for patients who are not able to consume large volumes of liquids, such as the elderly, and those who are suspected of having subtle right-side colonic lesions.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Adult
  • Aged
  • Cathartics / administration & dosage*
  • Colonoscopy / methods*
  • Drug Therapy, Combination
  • Female
  • Humans
  • Male
  • Middle Aged
  • Olive Oil
  • Plant Oils / administration & dosage*
  • Polyethylene Glycols / administration & dosage*
  • Probability
  • Prospective Studies
  • Reference Values
  • Sensitivity and Specificity
  • Therapeutic Irrigation / methods*


  • Cathartics
  • Olive Oil
  • Plant Oils
  • Polyethylene Glycols