Britannica Educational Publishing 
Kidneys and the Renal System [PDF ebook] 

Responsible for managing the body’s waste and regulating the balance of water and electrolytes, the kidneys and renal system, in a sense, make up the body’s plumbing network. When any part of the system fails or does not function properly, the body may be subject to unnatural concentrations of certain substances, causing illness or even death. This volume examines the various components of the renal, or urinary, system, and the consequences of dysfunction and disease.