Acute phosphate nephropathy is an accepted complication of the use of phosphate preparations in patients about to undergo colonoscopy. Age, renal failure, and the ongoing use of medications, such as angiotensin-converting enzyme inhibitors and/or angiotensin-receptor blockers, are now recognized as risk factors for the development of phosphate nephropathy. The presence of any of these risk factors necessitates careful attention to avoiding excessive dehydration in the process of bowel cleansing. In so doing, the likelihood of acute phosphate nephropathy occurring can be lessened.