Cleansing ability and tolerance of three bowel preparations for colonoscopy

This study was undertaken to determine whether different regimens using sodium phosphate (NaPh) solutions resulted in better bowel cleansing than polyethylene glycol-salt (PEG) solutions and, if so, why. Side-effects and patient acceptability of the different regimens were also investigated.

A total of 486 patients requiring colonoscopy were randomly assigned to one of three preparations in a single-blind prospective study. The preparations were as follows: Group A, 3 liters of PEG solution taken at 2 p.m. the day before examination; Group B, 45 ml of NaPh solutions taken at 7 a.m. and 7 p.m. the day before examination; or Group C, 45 ml of NaPh taken at 6 p.m. the day before and at 6 a.m. on the morning of, examination. Cleanliness of the bowel was assessed blindly, and patients were questioned about side-effects and preferences for NaPh vs. PEG.

Numbers, ages, and gender distribution of patients in the three groups did not differ significantly from each other. Cleanliness scores for the three groups were 3.34 +/- 0.97, 3.22 +/- 0.85, and 4.11 +/- 0.67 (Group C vs. Groups A and B, P < 0.0005; Group A vs. Group B, P > 0.30). Predominance of material in the right side of the colon was found in 13.7, 29.8, and 4.2 percent of Groups A, B, and C, respectively. In the three groups, nausea alone occurred in 3.8, 13.7, and 16.3 percent of patients; vomiting occurred in 0.6, 7.4, and 5.4 percent of patients; and dryness/thirst occurred in 1.9, 17.4, and 20.4 percent of patients, respectively. A total of 80.6 and 82.6 percent of those in Groups B and C who had previously had PEG expressed a preference for taking NaPh (P < 0.001).

The regimen of Group C is significantly better than the regimens of Groups A or B in bowel cleansing. Regimens of Groups A and B did not differ in efficacy of cleansing. It is the timing of taking NaPh in the regimen of Group C rather than its composition that is responsible for its superior cleansing ability compared with PEG. Overnight deposition of small intestinal material in the right colon is partly responsible for the inferior cleansing ability of regimens that involve taking the solution on the day before colonoscopy. Despite a higher incidence of minor side-effects from NaPh than from PEG, a significantly higher proportion of patients preferred NaPh.