[Detection and diagnosis of drug induced lithiasis]

Drug-induced calculi are often mis-diagnosed because of inadequate analysis of the urinary calculi. These stones can only be characterized unambiguously by global physical methods like infra-red spectrophotometry. From a series of 2,000 calculi analysed under infra-red, we identified 22, i.e. 1.1% of cases, which contained, partly or entirely, drug products. Ten other cases are still being studied. Amongst the products identified we found metabolites of glafenine (Glifanan) in 7 cases, triamterene and its derivatives (Cycloteriam) in 7 cases, metabolites of phenazopyridine (Pyridium) in 4 cases, sulphonamides in 2 cases : N-acetylsulphamethoxazole hydrochloride (Bactrim) and N-acetylsulphaguanidine (Guanidan), flumequine (Apurone) in 1 case and calcite (Cal-Mag-Na) in 1 case. The authors estimate that about 100,000 calculi are excreted in France each year and that at least 1,000 of these potentially contain drugs and are not diagnosed. Early recognition of drug induced stones is essential in order to protect the patient from recurrences, the risks of renal complications or, more simply, from useless therapeutic or dietetic regimes.