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Okay, so renal artery ultrasound is one of the classic applications of duplex

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imaging. And so these are going to be for patients who have renovascular

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hypertension. The primary question that the clinician wants to know is whether a

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flow-limiting stenosis is contributing to this hypertension or renal dysfunction,

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or if this is hypertension from another etiology.

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So how do we do the exam? Well, we evaluate a couple different things.

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Whenever we evaluate anywhere, we want to evaluate proximal, at, and distal to a

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site of stenosis. So because in this case, we are looking at the main renal artery,

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we are looking from that from the origin to the hilum.

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But we also want to evaluate the aorta, and we want to look at the intrarenal

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waveforms. So therefore, we looked at the aorta, which is the proximal portion,

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intrarenal waveforms, which are the distal portion.

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We also want to evaluate the renal vein, which is going to be key towards

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understanding the hemodynamics within the kidney.

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There are some direct criteria to describe renal artery stenosis.

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The first would be a peak systolic velocity of greater than 180 or 200 centimeters

1:04

per second. There is also a renal aortic ratio, and so if that ratio is greater

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than or equal to 3.5, that tends to be one of the ratios that not only in the renal

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but in the rest of the body is consistent with greater than a 60% or 70% stenosis.

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When the end-diastolic velocity also increases, in this case, greater than or equal

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to 150 centimeters per second, that is a slightly higher grade stenosis, where it's

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more consistent with greater than or equal to 80%.

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So you want to think about these ratios wherever you're thinking about in the body.

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Finally, we mentioned distal to it and what we might see, and if we want to see a

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true stenosis versus tortuosity in the main renal artery or just

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transient elevations, we would really like to see that there's also tardus parvus

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waveforms or decreased inflow within the kidney itself.

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So this can be particularly helpful when the proximal artery itself is difficult to

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visualize. If you do see that tardus parvus waveform, then you can have a much

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higher suspicion that there is a potential concern with the renal artery.

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And it may clue you into needing additional imaging, perhaps with a CTA or MRI.