Bowel preparation for colonoscopy: A randomized prospective trial comparing sodium phosphate and polyethylene glycol in a predominantly elderly population

Many patients find polyethylene glycol-based preparations (PEG) difficult to take because of the large volume of fluid they are required to consume. One hundred and sixteen predominantly elderly patients were randomized to receive either sodium phosphate (n = 61) or PEG (n = 55) bowel preparations before colonoscopy. Patients with a history of symptomatic ischaemic heart disease or cerebrovascular disease in the preceding 6 months, severe liver disease or heart failure, or serum creatinine above 200 mu g/L were excluded from the study. Each patient filled in a questionnaire about the bowel preparation prior to the procedure. The colonoscopists, who were not aware which preparation had been used, were asked to complete a questionnaire about the quality of the bowel preparation after the procedure. The patients found the sodium phosphate preparation slightly more tolerable than PEG. Side effects were slightly more common with sodium phosphate. Neither difference was statistically significant. However, 91% of patients who had previously had PEG found sodium phosphate easier to take. Approximately 25% of patients in each group experienced at least one episode of incontinence. The colonoscopists found no difference in the overall quality of the bowel preparation. The amount of fluid in the colon was greater in patients prepared with PEG. As expected, patients taking sodium phosphate developed hyperphosphataemia (mean phosphate level before colonoscopy 1.56 mmol/L, normal 0.8-1.3). They also had a lower mean serum potassium level (3.8 mmol/L) than the PEG group (4.2 mmol/L). However, there were no clinically significant consequences. Sodium phosphate was a safe and effective bowel preparation for colonoscopy in this carefully selected group of patients. It was preferred by patients who had previously had PEG. Many elderly patients were found to develop faecal incontinence, irrespective of the type of bowel preparation used.