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Bowel Cleansing Preparation: Is 2 Liters Enough?

Summary and Comment |
December 12, 2013

Bowel Cleansing Preparation: Is 2 Liters Enough?

  1. Douglas K. Rex, MD

Evidence is mounting toward the affirmative, yet methodological issues leave room for doubt.

  1. Douglas K. Rex, MD

Based on a recent meta-analysis, 4 liters of polyethylene glycol (PEG) 3350 with electrolytes given in split doses is still the gold standard of bowel preparations for efficacy. Although low-volume preparations have been shown to be noninferior to 4-L PEG with electrolytes in randomized, controlled trials, they have also been shown to have numerically higher failure rates in several trials (Am J Gastroenterol 2003; 98:2187).

To investigate this issue further, researchers assessed outcomes in 325 patients randomized to receive 2 liters of PEG electrolyte lavage solution (PEG-ELS) plus 15 mg of bisacodyl or 4 liters of PEG-ELS.

The low-volume preparation was noninferior as measured with both the Boston and Ottawa bowel preparation scales. However, the 4-L preparation had numerically superior efficacy scores in all colon segments according to both scales and was statistically superior in cleansing of the ascending colon according to the Ottawa scale. More patients in the 2-L group found the preparation easy or acceptable than in the 4-L group (90% vs. 75%, respectively; P<0.001) and reported willingness to repeat the same preparation (99% vs. 74%; P<0.001).

Comment

These results are consistent with those of other randomized, controlled trials in showing that low-volume preparations are better tolerated and noninferior in bowel cleansing efficacy. One problem with these results is that 15 mg of bisacodyl was included, whereas in the U.S., the only U.S. Food and Drug Administration–approved formulation containing bisacodyl (HalfLytely; Braintree Laboratories) was reduced several years ago to 10 mg and then to 5 mg because of reports of bisacodyl-induced ischemic colitis. In addition, as seen previously, 4-liter, split-dose preparations had numerically higher efficacy scores than low-volume preparations. This suggests the possibility that a type II error could be present, masking a truly higher failure rate with low-volume preparations. Thus, patients who are at increased risk for inadequate preparation (e.g., those with chronic constipation, prior colon resection, etc.) are sometimes still best prescribed a 4-liter PEG-ELS preparation or, alternatively, a low-volume preparation with additional laxative added.

  • Disclosures for Douglas K. Rex, MD at time of publication Consultant / Advisory board Exact Sciences; Ferring Pharmaceuticals; Given Imaging; Olympus Speaker’s bureau Boston Scientific; Braintree; Ferring Pharmaceuticals Grant / research support Battelle; Braintree; Northwestern University; Olympus America Editorial boards Annals of Gastroenterology and Hepatology; Comparative Effectiveness Research; Expert Review of Gastroenterology and Hepatology; Gastroenterology; Gastroenterology and Hepatology News; Gastroenterology Report; Gastroenterology Research and Practice; Journal of Clinical Gastroenterology; Techniques in Gastrointestinal Endoscopy; World Journal of Gastroenterology; World Journal of Gastrointestinal Oncology; World Journal of Gastrointestinal Pathophysiology; World Journal of Gastrointestinal Pharmacology and Therapeutics

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