Chinese herbal nephropathy and urothelial malignancy

In Belgium, between 1991 and 1992, seven women under the age of 50 years were admitted to a regional renal dialysis unit with progressive renal failure. All seven had been following the same slimming regimen, prescribed by the same clinic. They had an identical pattern of interstitial fibrosis on renal biopsy. Subsequently it became evident that all were at risk of developing urothelial malignant change. Could there possibly be a link to the prescribed drugs, which included Chinese herbs?