Nutcracker phenomenon

Last revised by Henry Knipe on 27 Oct 2020

The nutcracker phenomenon, also known as nutcracker anatomy or left renal vein entrapment, refers to the anatomic or pathophysiologic entity wherein the superior mesenteric artery compresses and impedes outflow of the left renal vein into the inferior vena cava. It can be a common incidental finding on routine CT imaging and many patients can be asymptomatic 2. If associated with relevant symptoms, it is then known as the nutcracker syndrome.

Radiographic features

Cross-sectional imaging demonstrates narrowing of the mesoaortic interval or angle as well as dilatation of the lateral (hilar) aspect of the left renal vein. There may also be dilatation of the gonadal vein with reflux of contrast material.

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Cases and figures

  • Figure 1: nutcracker (photo)
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  • Case 1
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  • Case 2
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  • Case 3: with SMA syndrome
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