0 Acute renal failure (ARF) is rarely reported after bowel preparation with sodium phosphate. We report a patient with mild Crohn disease (in remission), without history of renal disease, and with normal baseline renal function, who developed ARF 14 days after bowel preparation for colonoscopy with oral sodium phosphate. A renal biopsy showed multifocal calcium phosphate deposition in the renal tubules against a background of diffuse chronic tubulointerstitial injury. Review of the literature suggested 2 distinct patterns of ARF in the context of sodium phosphate bowel cleansing. One pattern is characterized by ARF, which develops a few hours or days after sodium phosphate administration, as a component of a systemic syndrome associated with severe hyperphosphatemia and bypocalcemia. Correction of these electrolyte abnormalities was frequently associated with rapid recovery of renal function. The cause of ARF in this context was not clear because the favorable outcome negated the need for renal biopsy. In the second pattern, exemplified by the current patient, ARF was identified incidentally. These patients did not have any features of an acute syndrome immediately after sodium phosphate administration and presented much later (usually weeks) with mild, nonspecific symptoms. At the time of presentation, the serum calcium and phosphate levels were normal. The renal biopsies in each of these patients showed nephrocalcinosis as the possible cause of ARF. The renal failure improved at least partially in most of these patients, but persisted in rare cases.