Kidney failure is a condition in which the kidneys are no longer able to filter waste from the blood adequately. It is also referred to as renal failure or renal insufficiency. Other synonyms for kidney failure include renal impairment, kidney dysfunction, kidney damage, and end-stage renal disease. These terms are used interchangeably and refer to the same condition. Kidney failure can occur suddenly or develop gradually over a period of time. It is a serious medical condition that requires prompt diagnosis and treatment. Early intervention can help slow the progression of the disease and improve the chances of successful treatment.