urine, clear, amber-colored fluid formed by the kidneys that carries metabolic wastes out of the body (see urinary system). As the blood circulates it collects excretory products from the tissues and these substances are separated from the blood by the kidneys and eliminated chiefly in the urine. The urine is then stored in the bladder and passes out of the body via the urethra. The amount passed depends on fluid intake and other factors. Urine is 95% water, in which are dissolved urea, uric acid, creatinine, and other waste products. Normal urine also contains small amounts of substances ordinarily utilized by the body, such as sodium, potassium, and calcium; these substances are excreted by the kidneys when excessive amounts are present in the bloodstream. Analysis of the urine is important in detecting diseases of the urogenital organs, as well as disorders of other body systems.