Medical causes of iatrogenic renal disorders

Nephrologists and other health care providers need to be aware of certain medications and diagnostic test preparations that, in some patients, can cause damage to the kidneys, according to a special clinical update being presented at the American Society of Nephrology's 40th Annual Meeting and Scientific Exposition in San Francisco.

The four presentations in this special Clinical Nephrology Conference (CNC) draw attention to several recently recognized "iatrogenic" (caused by medical treatments or tests) kidney disorders. Some of the problems are related to widely used products, including bisphosphonate drugs used to treat osteoporosis and "bowel prep" solution used to prepare for colonoscopy.

Dr. Daniel W. Coyne of Washington University School of Medicine, St. Louis, Mo., discusses the risk of kidney disorders associated with the use of bisphosphonates. Increasing evidence suggests that, in some circumstances, these widely used osteoporosis drugs can cause certain types of kidney damage. The risks are higher with "nitrogen-containing" types of bisphosphonate drugs and may depend on the individual patient and the total dose over time. Fortunately, the kidney damage is usually reversible after bisphosphonate treatment has stopped.

Despite these risks, bisphosphonates remain important in treating the high rate of osteoporosis in patients with kidney disease. Recent studies have even suggested that bisphosphonates can slow the buildup of calcium deposits in the blood vessels of patients on dialysis.

Dr. Glen S. Markowitz of Columbia University provides an update on the risks of acute and chronic renal failure related to the use of oral sodium phosphate solution. This product is widely used to prepare the bowels before procedures such as colonoscopy or surgery.

There is special concern about a rare but serious type of renal failure called acute phosphate nephropathy. Last year, the U.S. Food and Drug Administration issued an alert about this complication, including advice to avoid oral sodium phosphate solution in patients with kidney disease. Dr. Markowitz believes that the FDA warning, together with careful selection of the most appropriate "bowel prep" for individual patients, will reduce the number of patients with this condition.

Dr. Roger A. Rodby of Rush University Medical Center, Chicago, Ill., compares the risk of kidney injury caused by contrast agents containing iodine (used for computed tomography [CT] scanning as well as other imaging tests) to that associated with the use of gadolinium (used for magnetic resonance imaging [MRI]). The toxic effects of iodine on the kidneys have long been recognized. More recently, it has been found that newer gadolinium-based contrast agents may also cause kidney damage.

However, at typical doses, gadolinium-based contrast appears less toxic to the kidneys than iodine-based contrast. All reported cases of acute kidney failure linked to gadolinium have occurred in patients who already had advanced kidney disease. While the risk may be real, Dr. Rodby reminds physicians that patients with advanced kidney disease should probably not receive gadolinium anyway because of the association of exposure to gadolinium and the risk of another recently recognized complication, called nephrogenic systemic fibrosis.

Dr. Charles E. Alpers of University of Washington, Seattle, provides an update on drug-induced thrombotic microangiopathy (TMA)—a group of conditions in which clots form in the small blood vessels, causing damage to the kidney or other organs. Several different types of medications, including certain chemotherapy and immunosuppressive drugs, have been linked to TMA.

Immune-suppressing drugs called calcineurin inhibitors, which are very important in preventing rejection after organ transplantation, can cause a type of TMA leading to acute kidney failure. Fortunately, outcomes are better than with most other forms of TMA—kidney function generally returns after calcineurin inhibitor treatment is stopped. Dr. Alpers calls for more research to clarify how drug-induced TMA occurs, and to develop new treatment options.

"These presentations will help provide nephrologists with the most up-to-date information on iatrogenic renal disorders, helping them to play a key role in assessing patient risk for these disorders, recognizing them when they occur, and recommending the most appropriate treatment," states Kevin C. Abbott, MD, moderator of the program. Vivette D. D'Agati, MD will co-moderate this exciting program.