ĭoppler US examination of the renal vasculature plays a critical role in the evaluation of native as well as transplanted kidneys. The shorter right renal vein empties into the IVC laterally, noting that, when compared to the left, the right gonadal and adrenal veins drain into the right renal vein more infrequently in only 7 % and 31 % of cases, respectively. The most common congenital anomaly of the left renal venous system is the circumaortic left renal vein (consisting of anterior and posterior limbs that encircle the abdominal aorta) seen in up to 17 % of the population. ![]() During its course, the left renal vein receives almost always blood from the left adrenal and gonadal veins and, in the majority of patients, from the lumbar veins. The left renal vein passes between the aorta and the superior mesenteric artery before entering the IVC medially. The left renal vein measures 6 to 10 cm in length and is significantly longer than the right renal vein, which measures 2 to 4 cm. The renal veins generally lie anterior to the renal arteries at the renal hilum. The interlobular arteries supply the afferent glomerular arterioles, which, in turn, feed into the glomeruli. The segmental arteries supply end arteries to the renal parenchyma and divide further into lobar, interlobar, arcuate, and interlobular arteries. During their course, the renal arteries supply small branches to the adrenal gland, proximal ureter, and renal capsule however, these branches are usually not seen by US/imaging due to their small caliber.īefore entering the renal hilum and parenchyma, the main renal artery divides into five segmental branches, including apical, superior, middle, inferior, and posterior segmental arteries. The left renal artery arises more lateral of the aorta and courses almost horizontally to the left kidney posterior to the left renal vein. The right renal artery, which is longer than the left, arises from the anterolateral aorta and runs in an inferior course posterior to the inferior vena cava (IVC) to reach the right kidney. The main renal arteries are approximately 4 to 6 cm long with a 5 to 6 mm diameter. However, it should be noted that in approximately 30% of individuals, an accessory renal artery is present, and in 10 to 15 % on both sides. Typically, one renal artery and vein supply each kidney, with the arterial supply originating from the abdominal aorta, just below the level of the superior mesenteric artery, at the level of L1-L2. The kidneys are located in the retroperitoneum and receive approximately 20% of the cardiac output. ![]() ![]() In this article, we review the vascular anatomy, imaging indications, and technique, along with a short discussion about clinical significance and common pathologies. Nevertheless, due to its benefits, the American College of Radiology (ACR) Appropriateness Criteria guidelines rate renal Doppler US as appropriate or even first-line imaging technique in various clinical scenarios, especially in patients with decreased renal function or renal transplants when contrast administration for computed tomography or magnetic resonance imaging examinations might be problematic. Furthermore, the interpretation of renal Doppler US examinations might be challenging for those with limited experience or those unfamiliar with fundamental concepts and nomenclature. However, the technique is highly operator-dependent and can be time-consuming. As with other US examinations, advantages include its noninvasive nature, relatively low-costs, and generally well-tolerated. Doppler ultrasound (US) is a well-established and useful technique for evaluating the renovascular system and associated pathologic conditions.
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