The normal kidney longitudinal diameter is between 10.9 and 12 cm (median 10 cm), and the transverse extent is on average 5–6 cm, despite individual differences related to age and size. Patient’s preparation is very important for a correct US evaluation of the kidney. In subcostal scans with the patient in the left lateral decubitus position, the right renal artery can be evaluated along its entire length with a favorable sampling angle of <20°–30°. On the left side, however, the angle is less optimal, often exceeding 40°. The renal arteries originate from the anterolateral wall of the aorta, about 1.5–2 cm from the superior mesenteric artery. The knowledge of anatomic variants that come into differential diagnosis with various pathological conditions is very important.