Why To Do It Once a Year: The kidneys are composed of nephrons and tubules that are organized into a delicate meshwork that filter toxins from the bloodstream and produce an acidic urine. Your kidneys eliminate acids created daily by your metabolism and from your diet. It's important to do a kidney cleanse routine once or twice a year in order to release toxins that can clog the delicate filtering apparatus in the kidneys. Signs that your kidneys are toxic include high blood pressure, kidney stones, urinary tract infections, low back pain, eczema, rashes and other skin problems.