Hello Thanks for query . You are known to get recurrent urinary (Calcium Oxalate ) stones since last 20 years . The primary cause of getting recurrent stone is abnormal cacium metabolism and needs to be investigated Please consult qualified Urologist for clinical examination and get following basic tests done to find out the cause of getting stones 1) Urine routine and culture. 2) Stone analysis of a stone passed spontaneously 3) Blood test for Serum Calcium and phosphorus 4) Kidney function test. You have to follow following regime to prevent recurrence of stone 1) Ensure to drink more water 4-5 liters /day 2) Avoid extra salt in meals (Low sodium diet) 3) Take calcium and Oxalate together 4) Avoid vegetables containing phytates like Spinach ,tomato,cabbage etc 5) Avoid milk products 6) Avoid getting UTI. This should help to prevet stone recurrence to some extent. Dr.Patil.