Nature Clinical Practice Nephrology has recently published a review by Luyckx and Naicker highlighting the link between traditional medicines and kidney injury.

Traditional and herbal remedies are widely used worldwide, with as many as 80% of people in some populations using such treatments. The use of herbal remedies becoming increasing common in Western countries, as shown by a 2002 survey that found that 36% of people in the US use alternative or complementary medicines.

Herbal therapies all pass through the kidney on their way out of the body; consequently, many have been associated with acute kidney disease. Luyckx and Naicker report that “folk remedies account for up to 35% of cases of acute kidney injury and mortality rates for acute kidney injury range from 24% to 75%.”

The herbal remedies most commonly used in the US include echinacea, which is used as an immunostimulant, and St John’s wort, which is used to treat depression among other things. Echinacea, however, has been associated with acute kidney injury and St John’s Wort with kidney transplant rejection.

Various factors besides direct toxicity of the agent can contribute to kidney injury, such as contamination of the preparation or incorrect administration. In addition, the type of nephrotoxicity experienced by an individual taking a herbal remedy is dependent on which part of the kidney is affected, and the authors discuss these factors in more detail in their review.

Luyckx and Naicker do point out that the effects of herbal remedies are something of an unknown quantity; for example, some studies have shown that cranberry decreases the risk of kidney stones, whereas other studies find that cranberry increases this risk.

The review concludes by saying “The incidence and prevalence of acute kidney injury associated with the use of traditional remedies is unknown and probably varies greatly from place to place. Since the use of traditional remedies is common worldwide, it is probably safe to assume that the incidence of acute kidney injury is not high. Individual morbidity, however, can be considerable.”