Effect of Colonoscopy Preparation on Renal Function

Abstract

Purpose: Oral sodium phosphate (OSP) is commonly used for colonoscopy preparation. Cases of renal damage have been recently reported with OSP. We conducted a retrospective comparison of effect of OSP versus polyethylene glycol (PEG) on renal function. Methods: Chart review was performed on 230 patients who underwent colonoscopy (144 prepared with OSP and 86 with PEG). Subjects included had serum creatinine of ≤ 1.5 mg/dl within 6 months prior to colonoscopy and follow-up creatinine within 3 months after colonoscopy. Parameters used for deterioration of renal function (expressed as mean ± SEM) were change in serum creatinine, ratio of change over baseline creatinine, and proportion of patients with > 50% increase in this ratio. Results: Compared to patients given PEG, those receiving OSP were younger (69.6 ± 1.2 vs. 65.9 ± 1.0 years, p= 0.02) and less likely to have hypertension (72.2% vs. 56.4%, p= 0.02). Proportion with diabetes mellitus was similar in two groups (62.5% vs. 62.7%, p= 0.963). Use of OSP slightly increased creatinine from baseline of 1.0 ± 0.02 to 1.1 ± 0.02 mg/dl (p= 0.01 by paired t-test). Eight patients (5.6%) had > 50% increase in creatinine from baseline. Using logistic regression, there was no significant association of age, diabetes, hypertension, or baseline creatinine with worsening renal function. Compared with PEG, OSP resulted in no significant increase in creatinine (0.02 ± 0.04 vs. 0.05 ± 0.02 mg/dl, p= 0.10) and ratio of change in creatinine/baseline (0.015 ± 0.037 vs. 0.070 ± 0.020, p= 0.16). There was no significant difference in PEG vs. OSP with respect to proportion of patients with > 50% increase in creatinine from baseline (4.6% vs. 5.6%, p > 0.9). Two of the PEG patients had post-prep serum creatinine >2.0 as compared to 1 patient in the OSP group. No patient developed clinically significant acute or chronic renal failure. Subgroup of patients with baseline creatinine ≤ 1.3 mg/dl had no significant difference in change in creatinine or ratio of change in creatinine/baseline. Conclusions: In this retrospective study, clinically significant deterioration of renal function was uncommon with OSP or PEG in patients without renal disease. However, a small percentage of patients did develop mild deterioration of renal function which could not be predicted. OSP appears to be safe in patients with normal renal function.