Ultrasound is commonly used in nephrology for diagnostic studies of the kidneys and lower urinary tract and to guide percutaneous procedures, such as insertion of hemodialysis catheters and kidney biopsy. Nephrologists must, therefore, have a thorough understanding of renal anatomy and the sonographic appearance of normal kidneys and lower urinary tract, and they must be able to recognize common abnormalities. Proper interpretation requires correlation with the clinical scenario. With the advent of affordable, portable scanners, sonography has become a procedure that can be performed by nephrologists, and both training and certification in renal ultrasonography are available.