Prospective Assessment of Renal Impairment After Preparation for Colonoscopy: Oral Sodium Phosphate Appears to Be Safe in Well-Hydrated Subjects with Normal Renal Status

Background The outcome of colonoscopy is highly dependent upon the quality of bowel cleansing prior to the procedure. Oral sodium phosphate solutions (OSPS) or preparations containing polyethylene glycol (PEG) are generally employed. However, the safety of administering OSPS prior to colonoscopy has been questioned because of the potential for renal failure. Aim To compare rates of renal failure after OSPS and PEG in a randomized, prospective trial and to assess the quality of colonoscopy after these two bowel preparations. Methods Subjects with eGFR ≥ 60 ml/min/1.73 m² and expressed willingness to adhere to hydration recommendations were randomized to OSPS or PEG solutions. Renal function was assessed 1 week prior to, immediately prior to, and 1 week after colonoscopy. Results No subject had acute kidney failure after OSPS or PEG. OSPS was associated with significant increases in the serum phosphate and sodium levels and significant decreases in the calcium and potassium levels. These values returned to normal limits in all subjects by 1 week after colonoscopy. The quality of colonic cleansing was superior after OSPS than after PEG (Ottawa score 2.5 ± 2.2 vs. 3.5 ± 2.3, respectively, P < 0.05). The detection of one or more adenomatous polyps was higher after OSPS than after PEG. Conclusions Renal failure was not detected after the use of OSPS for colonoscopy preparation in subjects with recently documented normal renal function who were able to consume the required amounts of water after each dose. However, based on the number of subjects studied, the theoretical risk of this complication is still between 0 and 6.3%. Thus, it is appreciated that only a very large prospective trial would have yielded a more accurate estimate of the likelihood of renal compromise after OSPS. Despite this caveat, OSPS has advantages over PEG in terms of the adequacy of colonic visualization and the number of polyps detected.