Crystals are caused by the formation of minerals, such as calcium oxalate
Crystals are the formation of crystalline structures in the urinary tract (which includes the kidneys, ureters, and bladder). They form when your urine contains more crystal-forming substances — such as calcium, oxalate and uric acid — than the fluid in your urine can dilute. At the same time, your urine may lack substances that prevent crystals from sticking together, creating an ideal environment for crystals to form.
Bodily Waste and Liquid Ratio
Urine contains various bodily wastes. When there is too much waste in too little liquid, crystals begin to form. The crystals often attract other elements which join together to form a solid that will get larger unless it is passed out of the body. Usually, these chemicals are eliminated in the urine by the kidney.
In most people, having enough liquid, especially water, will wash theses wastes and solids out of the body and the kidney will contain other chemicals in the urine to help stop a crystal from forming. The basic crystal forming chemicals are calcium, oxalate, urate, cystine, xanthine and phosphate.
Most crystals (80% or more) occur when calcium combines with one of two substances: oxalate or phosphorous.
After a crystal is formed, the crystal may stay in the kidney or travel down the urinary tract into the ureter. Sometimes, tiny crystals move out of the body in the urine without causing too much pain. Crystals that don’t move may cause a back-up of urine in the kidney, ureter, the bladder or the urethra. This is generally what causes very severe pain.