Stones can be found any where in the urinary tract but usually they are formed in the kidneys and then are lodged at other sites. Smaller stones can pass in the urine but larger stones can impact anywhere in the urinary tract extending from the kidneys to the urethra. 

Due to the buildup of back pressure in the presence of an obstructing stone; the kidneys can be harmed and even destroyed. 

Some stones are large enough to damage the kidney due its own pressure effects. Stones also invite infections in the urinary tract. Long standing urinary tract infection by itself can cause renal failure. 

The common varieties of the kidney stones are

• Calcium Oxalate stone (35-70%)
• Calcium phosphate stone (10-45%)
• Triple Phosphate or Staghorn stone (10%)
• Uric acid stone (5-10 %)
• Cysteine stone (Very rare)

Uric acid and Cysteine stones are radio translucent and are not visible on plain x-ray abdomen.