Because tuna steak generally contains higher levels of mercury than canned light tuna, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of tuna steak per week.
Each about the size of a fist, these organs act as sophisticated filters for the body. They process about 200 quarts of blood a day to sift out about 2 quarts of waste products and extra water that eventually leave the body as urine. Blood enters the kidneys through arteries that branch inside the kidneys into tiny clusters of looping blood vessels. Each cluster is called a glomerulus, which comes from the Greek word meaning filter. The plural form of the word is glomeruli. There are approximately 1 million glomeruli, or filters, in each kidney. The glomerulus is attached to the opening of a small fluid-collecting tube called a tubule.
Urine Tests. One of the primary functions of the kidneys is to filter blood and remove waste products. Urine tests measure how well your kidney filters (see figure) are working. When functioning normally, glomerular filters are able to filter out wastes, but keep protein and red blood cells in the bloodstream.