Tumors on the kidneys (renal masses) are assessed through CT scans and ultrasound techniques. In the past such tumors would otherwise have remained totally hidden and completely asymptomatic (without symptoms) until they had grown sufficiently large to cause either gross or microscopic blood in the urine, leading to studies to establish a diagnosis. Now, kidney cancers are more often diagnosed when they are smaller and blood in the urine may not necessarily be observed.