Beasley, Allen, Crow, Methvin, Portis & Miles, P.C.

After years of serious adverse events following the use of a type of solution used to clear the bowel before colonoscopies, Oral sodium phosphates (OSP), the products are no longer available over-the-counter and the ones available by prescription, known by the brand names Visicol and Osmo Prep, now carry a black box warning that a serious form of kidney injury has been associated with the use of the products.

Even if patients aren’t diagnosed with the type of renal failure associated with OSP use, known as Acute Phosphate Nephropathy, they may still be at risk from conditions due to electrolyte abnormalities, according to an article, Is Bowel Preparation Before Colonoscopy a Risky Business for the Kidney? published in MedScape CME.

OSPs are saline laxative solutions that work by drawing liquid from the body into the colon, which can cause severe hydration. Hydrating during use is optimal, but isn’t always the answer to keeping patients safe.

All patients who take the standard dose of OSP will develop hyperphosphatemia, an electrolyte disturbance in which there is an abnormally elevated level of phosphate in the blood. Patients with increased gastrointestingal absorption of phosphate or decreased renal excretion may develop severe hyperphosphatemia. Fatal cases of hyperphosphatemia have been reported inpatients receiving more than the standard dose of OSP and in those with renal failure.

All patients will also experience another electrolyte imbalance called hypocalcemia, or low serum calcium levels in the blood. Elderly patients are particularly prone to the condition.

A third type of electrolyte disturbance is hypokalemia, a condition in which the concentration of potassium in the blood is low. Potassium is essential for many body functions including muscle and nerve activity. A serious increase or decrease of potassium may promote heart arrhythmias.

Mild hypernatremia, or elevated sodium levels known also as dehydration, is common after OSP use, particularly in the elderly. Severe elevations of sodium can lead to seizures, coma and even death. At least two patients have experienced hyponatremia, or abnormally low sodium levels in the blood, following use of OSP, likely caused by excessive free water intake.

The MedScape CEM summary advises health care professionals: “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.”

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