Kidneys are two bean-shaped organs about the size of a fist located on either side of spine in the abdomen at the lower back just below the rib cage. Kidneys produce urine and not only cleanse the blood of wastes but also maintain normal fluid, salt,and mineral levels in the body. Hence, they also play a key role in maintaining blood pressure. They also produce hormones such as erythropoietin and calcitriol (active vitamin D) and produce the enzyme renin.

In kidney disease, the damage is usually to the nephrons (the functional units of the kidney). Kidney disease can either be acute or chronic. Research is being done to develop new therapies using stem cells to treat kidney disease, reducing the need for dialysis and transplantation.