Cystatin C is a cysteine protease inhibitor that is produced at a constant rate by all nucleated cells in the body and released into the blood stream . It is also freely filtered by the renal glomerulus and then metabolized by the proximal tubule . Cystatin C is a novel marker that can be used as a measure of renal function. It possesses several interesting properties making it a prospective marker of renal function in clinical practice.