HOW DO KIDNEY STONES FORM?

Everyone forms crystals in their urine, even people who never form kidney stones. Urine, which is produced in the kidneys, naturally contains substances that promote the development of crystals. These stone promoters include calcium, oxalate, sodium, phosphorus and uric acid (and also cystine, in the case
of individuals with the inherited disorder known as cystinuria).

These stone-promoting compounds, which come from the bloodstream, are present in urine because the kidneys filter our blood and regulate whether and how much of these urinary constituents will be reabsorbed by the kidneys (put back into blood circulation) or eliminated as waste.

In addition to these stone promoters, urine also naturally contains proteins and other compounds that inhibit crystal formation. Examples of stone inhibitors in urine include total urine volume, citrate, magnesium, pyrophosphate, phytate and proteins and other molecules derived from normal metabolism, collectively referred to as urinary macromolecules. These inhibitor said the elimination of crystals before they attach to the kidney and grow into larger stones.

Thus, if the crystals remain small enough, and if the urine is dilute enough to avoid super saturation, crystals will flow with urine through the ureters and bladder without being noticed or causing problems. However, this balance between stone promoters and inhibitors does not exist for everyone - either due to genetic, lifestyle or other factors - leading to the formation of kidney stones.