Final answer:
Kidney failure, or renal failure, is the condition when the kidneys are not being perfused adequately. This can result from various conditions and can lead to a build-up of toxic waste substances in the blood.
Step-by-step explanation:
When the kidneys are not being perfused adequately, it is known as kidney failure or renal failure. This can occur as a result of various conditions such as diabetic nephropathy, polycystic kidney disease, liver failure, vascular problems, or infection. Kidney failure can lead to a build-up of toxic waste substances in the blood, which can have devastating effects on the body's homeostasis.