What is your approach for managing patients with recurrent nephrolithiasis who have elevated urinary cystine levels but calcium oxalate stone composition?  

This is usually heterozygous cystinuria, and the urine cystine is in the range of 50 mg. Supersaturation with cystine is absent, and the cystine can be ignored. Rarely, urine cystine is high enough to produce stones, and I treat both stone risk factors. In all cases where urine cystine is above 100 ...