The right kidney sits lower than the left kidney in the human abdomen. This is to allow space for the liver. The liver sits just above the right kidney and it is a very large organ so it needs space. The kidneys sit against the back muscles in the upper abdomen. They sit opposite each other on either side of the spine. Each kidney is shaped like a bean and its function is to extract waste from the blood, create urine and balance the fluids in the human body.