Painful Precipitates-Kidney Stones

Each year, more than a million people in the United States are hospitalized because of very painful kidney stone attacks. a kidney stone is a hard mass developed from crystals that separate from the urine and build up on the inner surfaces of the kidney. the formation of the stones is caused primarily by buildup of Ca2+, C2O43-, and PO43- ions in the urine. when the concentrations of those ions become large enough, the urine becomes supersaturated with respect to calcium oxalate and/or calcium phosphate and precipitates begin to form (70% to 80% of all kidney stones are made up of calcium oxalate and phosphate). 

If the crystals remain tiny enough, they can travel though the urinary teact and pass out of the body in the urine without being noticed. sometimes, however, they continue to grow without being passed and can cause intense pain if they become stuck in the urinary tract. kidney stones don't all look alike. their color depends on what substances are mixed with the inorganics precipitates (e.g., proteins or blood). most are yellow or brown, as seen in tje accompanying photo, but they can be tan, gold or even have branches. They vary in size from mere specks to pebbles to stones as big as golf balls!

Source = Brady, James E. 2009. Chemistry Fifth Edition. Asia : John Willey & Sons