The kidneys are a pair of fist-sized organs located in the back that serve as a filtration system to filter liquid waste from the blood and remove it from the body in the form of urine. Kidneys adjust the body’s balance of various chemicals (sodium, potassium, calcium, phosphorous and others) and monitor the blood’s acidity. Certain hormones are also produced in the kidneys. These hormones help regulate blood pressure, stimulate red blood cell production and promote strong bones. The ureters are two muscular tubes that transport the urine down to the bladder.