Kidney stone (also known as ureterolithiasis) surgery is required when the pain from kidney stones is persistent and severe, in renal failure and when there is a kidney infection. Finding a significant stone before it passes into the ureter allows physicians to fragment it surgically before it causes any severe problems. In most of these cases, non-invasive Extracorporeal Shock Wave Lithotripsy (ESWL) will be used. Otherwise some form of invasive procedure is required; with approaches including ureteroscopic fragmentation.