Human kidneys clean 200 quarts of blood every day for decades on end, but most people don't give these hard-working organs much thought. We're more likely to worry about the filters in our cars than the ones in our bodies. Kidneys are too important -- and too vulnerable -- to take for granted. Millions of Americans are living with kidney disease, and many don't even know it. How much do you know about your kidneys? Take this short quiz to find out.
