Acute kidney failure (renal failure) or acute kidney injury is when your kidneys suddenly stop working properly. This means that they are unable to remove salt, water and waste products from the bloodstream.
When Callum, from North Shields, was 12 years old his kidneys failed. Years later, after a successful transplant, Callum went on to win gold at the Transplant Games. Here, Sue tells her family's story.
Erythropoiesis stimulating agent (ESA) medicines are man-made versions of erythropoietin, which is a hormone (chemical messenger) produced naturally by the kidneys. The role of erythropoietin is to stimulate the bone marrow to produce more red blood cells.