Between 1990 and 1992, each had used a Chinese herbal remedy in combination with two other drugs for weight loss. The herbal preparation supposedly contained Stephania tetrandra and Magnolia officinalis . But the sudden appearance of kidney failure in these patients, caused their doctors to suspect that the herb Aristolochia fangchi , which is poisonous to the kidneys, had unintentionally been substituted for S. tetrandra . The Chinese names for A. fangchi and S. tetrandra sound similar and the two are often confused. Analysis showed that the herbal remedy did, in fact, contain aristolochic acids, which are derived from A. fangchi.
Aristolochic acids cause cancer in rats and mutations in bacteria and mammals.
When one of their patients also developed this cancer, the doctors decided that all patients with end-stage kidney failure related to the use of Chinese herbs should be checked for cancer of these organs. By removing these organs, the doctors hoped to prevent cancer from developing in their patients. Thirty-nine of the 43 patients agreed to undergo the preventive surgery. The investigators also analyzed DNA samples taken from the kidneys and ureters of each patient. The DNA samples for every patient showed changes typically found after exposure to aristolochic acid.