Medullary sponge kidney, stones occur in tiny cysts formed in the kidney, giving it a sponge like appearance.
A lithotriptor is a medical device used in the non-invasive treatment of kidney stones (urinary calculosis) and biliary calculi (stones in the gallbladder or in the liver). The scientific name of this procedure is Extracorporeal Shock Wave Lithotripsy (ESWL).
The lithotriptor attempts to break up the stone with minimal collateral damage by using an externally-applied, focused, high-intensity acoustic pulse.
ESWL is the least invasive of the commonplace modalities for definitive stone treatment, but provides a lower stone-free rate than other more invasive treatment methods, such as ureteroscopic manipulation with laser lithotripsy or percutaneous nephrolithotomy (PCNL). The passage of stone fragments may take a few days or a week and may cause mild pain. Patients may be instructed to drink as much water as practical during this time.
Normally stones pass out by themselves but in your case you might want to discuss the above option with your doctor.