Urinary cystine stone crystals (M. Daudon, CRISTAL Laboratory)
The first line of treatment for this condition (or, for that matter, ANY affliction of a urinary tract stone former) is copious hydration and dietary sodium limitation so as to minimize the concentration of urinary solutes that might precipitate into stones. Also, dietary protein limitation will reduce the amount of substrate for urinary cystine, thus reducing urinary cystine. In some of the more fortunate cystinurics, these measures may suffice. If hydration alone fails to reduce urinary cystine concentration below it’s solubility threshold, raising the urine pH to at least 7.5 with potassium citrate (Urocit–K) can dissolve the cystine by bringing the urine’s pH closer to it’s solubility point pK.