Is bowel preparation before colonoscopy a risky business for the kidney?

Acute phosphate nephropathy after bowel preparation with oral sodium phosphate (OSP) for colonoscopy has emerged as an important clinical entity. In 2004, five cases of nephrocalcinosis and irreversible renal failure after bowel preparation with OSP were reported. More recently, several retrospective studies have shown that the incidence of acute kidney injury after OSP use is in the range of 1-4%, similar to the incidence of contrast nephropathy in the general population. The degree of renal failure is not generally as severe as in the first reported cases, but irreversible damage can still occur. Millions of people worldwide undergo screening colonoscopies for colon and rectal cancer after the age of 50, so careful patient selection and monitoring for possible complications is essential when OSP is used. In addition to educating patients about the possibility of renal damage, physicians should routinely watch for considerable weight loss during bowel preparation and correct the fluid deficit as needed. Carrying out a renal function panel, which includes serum phosphorus level, is prudent after colonoscopy. Alternative bowel cleansing agents are needed because calcium phosphate precipitation is inevitable after OSP use even in the normal kidney.