Risk of impaired renal function after colonoscopy: a cohort study in patients receiving either oral sodium phosphate or polyethylene glycol.

Objectives: We aimed to evaluate frequency, predictors, and monitoring of renal dysfunction related to the use of oral sodium phosphates for colonoscopy in clinical practice.

Methods: Cohort study using clinical records and electronic patient information from the Henry Ford Health System, Detroit, MI. We identified patients undergoing colonoscopy using sodium phosphate or polyethylene glycol (PEG), and estimated the risk of renal impairment associated with bowel preparation and other risk factors.

Results: Out of 7,897 patients, 6,833 had used sodium phosphate; 1,617 patients had renal dysfunction within 12 months prior to colonoscopy and 3,928 patients had no creatinine measurement within 12 months prior to or 6 months postcolonoscopy. Among the remaining 2,352 patients, 88 had incident renal dysfunction (glomerular filtration rate [GFR]<60 mL/min) after colonoscopy. The relative risk (RR) estimate for renal dysfunction comparing sodium phosphate with PEG was 1.13 (95% CI 0.58-2.23) without adjustment, and 1.14 (95% CI 0.55-2.39) after multivariate adjustment. Significant univariate risk factors were age>or=65 yr, African-American race, low baseline GFR, hypertension, and use of angiotensin-converting enzyme inhibitors (ACE inhibitors), angiotensin-renin blockers, or thiazide diuretics.

Conclusions: In patients without preexisting renal disease, the risk of renal impairment after colonoscopy appears to be similar between sodium phosphate and PEG users. Sodium phosphate use in patients with preexisting renal disease is not recommended, but common in clinical practice. Sodium phosphate should not be used in patients with preexisting serious renal disease, adequate hydration should be assured in all patients, and renal function should be monitored before and after colonoscopy in those at risk of renal dysfunction.