A bladder can hold over a pint of urine. During urination, the urethra carries urine from the bottom of the bladder out of the body. Kidney stones are hardened crystal clumps that can develop in the urinary system. They usually form because there is a breakdown in the balance of liquids and dissolved solids in the urine. The kidneys must keep the right amount of water in the body while they remove materials that the body cannot use.
Crystals begin to stick together and slowly add layer upon layer to form a stone.
A kidney stone may grow for months or even years before it causes a problem. Kidney stones don't all look the same. The color depends on what chemicals are in it. Most are yellow or brown, but they can be tan, gold, or black. Stones can be round, jagged, or even have branches.