Most people know that a major function of the kidneys is to remove waste products and excess fluid from the body. The kidneys are two bean-shaped organs in the renal system. The kidneys' job is to filter your blood. What is the Function of Our Kidneys? The kidneys are a very important organ in the body. Assessment of kidney function occurs in different ways, using the presence of symptoms and signs, as well as measurements using urine tests, blood tests, and medical imaging.