![]() Catheter angiography is considered the gold standard examination for this type of evaluation but is limited by its invasive nature and the fact that it exposes patients to iodinated contrast material and radiation. There are a number of other imaging modalities that evaluate the renal vessels, each of which has strengths and weaknesses. The key to the renal Doppler examination is accurate demonstration of the vascular anatomy. Literature reports indicate that as many as 95% of main renal arteries can be adequately examined in adult patients. With time and experience, however, sonographers become adept at this study and are able to perform the examination in a reasonable period of time. The examiner is required to have an understanding of the renal anatomy, normal waveform physiology, and image optimization techniques. Rarely, renal arteries may arise from the superior mesenteric, inferior mesenteric, celiac, middle colic, or sacral arteries.ĭoppler ultrasound evaluation of the renal arteries is one of the more challenging examinations to perform, given the small size of the renal vessels, their depth, and variable anatomy. Both accessory and polar renal arteries commonly go unrecognized on ultrasound, but even duplicated main renal arteries may be overlooked sonographically. Polar renal arteries do not enter the renal hilum but rather course directly to the cortex of one of the renal poles, and similar to accessory renal arteries, they may originate either from the aorta or iliac arteries. Accessory renal arteries also travel to the renal hilum but may arise from the aorta or the iliac arteries and supply smaller distinct segments of the renal parenchyma. Duplicated renal arteries are defined as arteries that arise from the aorta, course toward the renal hilum, and supply similar proportions of the renal parenchyma ( Fig. When more than one renal artery is present, the diameter of the renal arteries is variable, although they are generally smaller than when there is a single main renal artery. On average, the main renal arteries measure approximately 4.6 mm in anteroposterior (AP) diameter. The three most common anatomic variations of the renal arterial circulation are: duplicated main renal arteries, accessory renal arteries, and polar renal arteries. Each kidney is supplied by a single renal artery in only 70% of the population, with the remaining 30% supplied by multiple vessels. It has a direct upward course to the more superiorly positioned left kidney ( Fig. The left renal artery arises below the level of the right renal artery origin and is more horizontally oriented. The right kidney is relatively inferior to the left kidney, which explains the downward course of the right renal artery, traversing posterior to the IVC and right renal vein. ![]() No other vessels course behind the aorta, and when a vascular structure is seen behind the aorta, a renal vein anomaly should be considered ( Fig. ![]() The most common and most significant anatomic variants of the renal venous system are a circumaortic left renal vein, when one of the limbs of the left renal vein courses anterior to the aorta and another runs posterior to it and a retroaortic left renal vein, when the left main renal vein lies posterior to the aorta. The left renal vein lies between the superior mesenteric artery and the aorta (as opposed to the splenic vein, which lies anterior to the superior mesenteric artery). Anterior to each renal artery runs a corresponding renal vein, and both vessels course anterior to the renal pelvis before entering the medial aspect of the renal hilum ( Fig. The left renal artery generally arises from the lateral or posterolateral aspect of the aorta. It is the only major vessel that courses posteriorly to the IVC. The right renal artery arises anterolaterally from the aorta and passes posterior to the inferior vena cava (IVC). ![]() The renal arteries arise from the proximal abdominal aorta just below the origin of the superior mesenteric artery, which serves as a reference point ( Fig. Each kidney receives its arterial supply from one or more renal arteries.
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