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 hematuria (blood in urine).
In certain situations the syndrome can result from a retroaortic/anterior 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.
