A hereditary factor has been reported, but environmental factors apparently play the predominant role, as family members living in the patient's household have stones more often than blood relatives who live elsewhere. The higher the calcium level excreted in the urine the higher the risk of stone formation. The Southeastern states report the highest incidence, probably reflecting the longer periods of warm weather. New England reports the second highest incidence. About half of all stones formed will pass spontaneously, the balance require surgical removal.
Most kidney stones are calcium oxalate or calcium oxalate combined with calcium phosphate.
Symptoms of urinary stones vary. If the stone does not obstruct urine flow it may not produce symptoms and the first indication of urinary stone may be the expulsion of the stone though the urethra. Pain is by far the most common symptom, and may be provoked by slight physical disturbance such as automobile travel. Onset of the pain is generally sudden and severe. The patient may not be able to remain still for even an instant.