Stones can be formed any where in the urinary system, like kidney, ureter, and bladder. The process by which the stone formation occurs is Supersaturation of urine. All stones are formed in the kidneys, initially as small particles. These particles grow within the kidney to varying sizes, often filling up the whole kidney as a branched stone (the staghorn calculus). Sometimes they move out of the kidney when relatively small, and then migrate down the ureter into the bladder. Some stones less than 5 mm in size pass out spontaneously, but occasionally they migrate down the ureter & they may block the ureter causing obstruction to the flow of urine. This results in pain, which may be very severe (ureteric colic). Nausea and vomiting can also be associated with the colic pain. Some stones reach the bladder, and lodge there, growing larger and larger. Rarely do they block the urethra causing a painful retention of urine.

Once a stone has been diagnosed, the choices is between expectant treatment and more aggressive forms of treatment, such as transurethral, percutaneous, or open surgeries or the relatively new extra corporeal modalities. Although some stones may pass spontaneously and unless complicating conditions arise, surgical intervention may not be necessary. Thus, identification of stones that are likely to pass is of utmost importance. The primary decision is weather to apply surgical treatment or wait. Removal of stones by any methodology is necessary when there is evidence of Significant Obstruction, Progressive Deterioration of the Kidney, Irreversible Infection of the kidney, Unremitting Pain, Stone Obstruction an infected kidney requires emergency intervention.