The effect of oral sodium phosphate drug products on renal function in adults undergoing bowel endoscopy.

Background: Oral sodium phosphate solution (OSPS) preparations are preferred cleansing agents for colonoscopy because of ease of use and excellent preparation quality. Besides causing acute renal failure in some patients, the high phosphorus content can potentially cause chronic kidney damage to patients undergoing colonoscopy.

Methods: We carried out a retrospective study on patients with creatinine levels in the normal range who had undergone colonoscopy or flexible sigmoidoscopy using OSPS preparation from January 1998 to February 2005 and followed them for 1 year to determine its effects on their renal function. A control group of patients with similar comorbidities during this period were chosen to assess age-related decline in renal function in this population.

Results: A total of 286 patients were selected in the study group, and 125 patients were selected in the control group. Both groups had similar baseline characteristics. The baseline glomerular filtration rate (GFR) in the study group was 79 mL/min/1.73 m(2), which declined to 73 mL/min/1.73 m(2) at 6 months after exposure to OSPS preparation. This finding was significantly different from the control group, in whom the baseline GFR was 76 mL/min/1.73 m(2) and remained stable at 6 months. Linear regression analysis showed that use of angiotensin-converting enzyme inhibitors and/or angiotensin receptor blockers and the presence of diabetes were significant determinants of the fall in GFR after use of OSPS preparation.

Conclusions: Oral sodium phosphate solution preparation is associated with decline in GFR in elderly patients with creatinine levels in the normal range. Its routine use for elective and screening procedures should be discouraged in the elderly population.