Karen
I too have been diagnosed with meduallary sponge kidneys (bi-laterally). I was told it was a birth defect and most of the time you never have a problem with stones. I've had 3 surgical procedures since 1998 to remove hundreds of stones and put on a daily medication. Just 4 months ago my urologist sent me for a plain x-ray film and both kidneys are filled again with the stones. Drink plenty of water! I was also told it wasn't life-threatening or cause for alarm in terms of losing a kidney.