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.
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 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
- endovascular stent-graft placement 6
- 1. Little AF, Lavoipierre AM. Unusual clinical manifestations of the Nutcracker Syndrome. Australas Radiol. 2002;46 (2): 197-200. Australas Radiol (link) - Pubmed citation
- 2. Kavukcu S, Kasap B, Göktay Y et-al. Doppler sonographic indices in diagnosing the nutcracker phenomenon in a hematuric adolescent. J Clin Ultrasound. 2004;32 (1): 37-41. doi:10.1002/jcu.10222 - Pubmed citation
- 3. Takebayashi S, Ueki T, Ikeda N et-al. Diagnosis of the nutcracker syndrome with color Doppler sonography: correlation with flow patterns on retrograde left renal venography. AJR Am J Roentgenol. 1999;172 (1): 39-43. AJR Am J Roentgenol (abstract) - Pubmed citation
- 4. Muraoka N, Sakai T, Kimura H et-al. Rare causes of hematuria associated with various vascular diseases involving the upper urinary tract. Radiographics. 28 (3): 855-67. doi:10.1148/rg.283075106 - Pubmed citation
- 5. Hohenfellner M, D'elia G, Hampel C et-al. Transposition of the left renal vein for treatment of the nutcracker phenomenon: long-term follow-up. Urology. 2002;59 (3): 354-7. Urology (link) - Pubmed citation
- 6. Chen W, Chu J, Yang JY et-al. Endovascular stent placement for the treatment of nutcracker phenomenon in three pediatric patients. J Vasc Interv Radiol. 2005;16 (11): 1529-33. doi:10.1097/01.RVI.0000178259.87608.EC - Pubmed citation