A prospective blind trial on bowel cleansing methods for colonoscopy

Although some authors have suggested that sodium phosphate (NaP) is more effective than polyethylene glycol (PEG) in bowel cleansing, there has been no crossover study proving the superiority of NaP over PEG in bowel cleansing and patient's compliance. The aim of this study was to compare the two solutions for colonoscopy, PEG and NaP, by crossover design with regard to patient's compliance, cleansing ability and side effects. Twenty-one patients received two separate colonoscopies for rectosigmoid polyp(s) with PEG and NaP, respectively. Before and after bowel preparation, blood pressure, body weight and serum biochemical parameters were measured in all patients. A detailed questionnaire was used to assess side effects and patient's preference. The presence of bubbles, types of residual stool and overall quality of colon cleansing were assessed by one endoscopist blinded to the type of preparation used. In each colonoscopy, two biopsy specimens were taken at rectum. In the NaP group, but not in the PEG group, there were significant changes in several biochemical parameters including sodium (+3.3±3.0mEq/L), potassium (-0.4±0.3mEq/L), chloride (+2.6±3.0mEq/L), bicarbonate (-2.7±2.2mEq/L), calcium (-0.6±0.4mg/dL), phosphorus (+3.7±2.3mg/dL) and osmolarity (+11.4±10.4mOsm/kg) after bowel preparation. In addition, the change in body weight was greater in the NaP (-2.3±2.7kg) than the PEG group (-1.2±1.6kg) (p<0.01). The formation of bubbles that prevent the detailed examination of colonic mucosa was more frequently observed in the NaP group (p<0.01). However, there was no difference in the type of residual stool and the overall quality of bowel preparation between the two groups. No significant mucosal change was noted after bowel preparation in both groups. Moreover, abdominal bloating was less common with NaP (p<0.05) and among the 21 patients, 18 (86%) preferred NaP to PEG, while only one favored PEG (p<0.01). We conclude that NaP can replace PEG at least in patients with good general condition. Further studies to decrease the incidence of bubbles and to establish subgroups suitable for NaP are needed.