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 (Wilkie syndrome) also a superior mesenteric artery compression disorder, where the SMA compresses the third part of the duodenum (the two conditions however may be associated).

There is a slightly greater female predilection.

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. 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.

  • may occur simultaneously with SMA syndrome
  • an association with a thin or asthenic body habitus has long been noted.

Radiographic features are similar on ultrasound, Doppler ultrasound, CT, MRI, and conventional angiography:

  • reduced aortic-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
  • compression ratio (CR) given by the equation CR=P-C/C i.e. diameter of pre-compressed vein (P) minus diameter of compressed vein (C) divided by the diameter of the compressed vein (C). A compression ratio above 2.25 is highly sensitive and specific for Nutcracker syndrome 10.

Persistent haematuria can precipitate renal vein thrombosis 4.

Treatment should be started strictly when it is causing symptoms (haematuria and left flank pain). Surgical treatment modalities have their 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

The first clinical report of this syndrome was made by El-Sadr and Mina in 1950 while the term "nutcracker syndrome" is thought to have been first used by de Schepper in 1972 7.

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Article information

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

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