Nutcracker syndrome

Nutcracker syndrome is a vascular compression disorder, and refers to the compression of the left renal vein between the superior mesenteric artery (SMA) and aorta. This can lead to renal venous hypertension, resulting in rupture of thin-walled veins into the collecting system with resultant haematuria.

In certain situations the syndrome can result from a retroaortic or circumaortic left renal vein which then also referred to as the posterior nutcracker phenomenon 3.

Nutcracker syndrome should not be confused with superior mesenteric artery syndrome (aka Wilkie syndrome) also a superior mesenteric artery compression disorder, where the SMA compresses the third part of the duodenum.

Clinical presentation

The most common clinical manifestation of the nutcracker syndrome is intermittent macroscopic haematuria 3. Repeated episodes of gross haematuria and left flank pain should be present. Also, haematuria should be from the left ureteric orifice only 4. In the absence of clinical features, renal vein narrowing is usually developmental and not causing any pressure gradient, and thus should not be labelled as nutcracker syndrome.

Radiographic features

Radiographic features are similar on USG, Doppler, CT,  MR or conventional angiography:

  • reduced aorta: SMA angle (The normal angle between aorta and SMA is approximately 45° (38-65°).
  • left renal vein stenosis
  • collateral pathways: main collateral pathway is the left gonadal vein which will display early enhancement during portal venous phase
  • pressure gradient >3 mm Hg on renal venography


Persistent haematuria can precipitate renal vein thrombosis 4.

Treatment and prognosis

Treatment should be started strictly when it is causing symptoms (haematuria and left flank pain). Surgical treatment modalities have their own inherent complications, and should be contemplated only when strongly indicated. A few of the reported surgical choices are:

  • left renal vein transposition 5
  • superior mesenteric artery transposition
  • nephrectomy
  • endovascular stent-graft placement 6

See also

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Article Information

rID: 1745
Systems: Urogenital, Vascular
Section: Syndromes
Synonyms or Alternate Spellings:
  • Nutcracker phenomenon
  • Renal vein entrapment syndrome
  • Posterior nutcracker phenomenon
  • Left renal vein entrapment syndrome
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