Nutcracker Syndrome and Left Renal Vein Entrapment

Nutcracker syndrome, or left renal vein entrapment, is symptomatic compression of the left renal vein, often between the aorta and the superior mesenteric artery. Compression of the left renal vein causes venous congestion of the left kidney and distal structures. The clinical presentation of nutcracker syndrome is variable and may include flank pain, hematuria, proteinuria, varicocele, varices, dysmenorrhea, and, less commonly, hypotension and tachycardia. Nutcracker syndrome can result in significant morbidity, including chronic renal disease and venous thrombosis. The anatomical finding of left renal vein compression between the aorta and superior mesenteric artery was first described by the anatomist Grant in 1937; de Schepper is frequently credited with naming the anatomical finding in 1972. Nutcracker syndrome describes patients as symptomatic from the anatomical anomaly, while the nutcracker phenomenon refers to the anatomic finding in the absence of symptoms. Asymptomatic left renal vein compression found incidentally on imaging is considered a normal variant. While nutcracker syndrome can affect all age groups, it is thought to peak during the second and third decades, concurrent with the completed maturation of the vertebral bodies.  There are two main anatomical configurations of nutcracker syndrome: Anterior nutcracker syndrome is the more common variant and describes the situation where the left renal vein is compressed between the aorta and the superior mesenteric artery. The less common variant is posterior nutcracker syndrome, in which the left renal vein is compressed between the aorta and the vertebrae. Left renal vein compression can also occur from other causes, such as malignancy, lymphadenopathy, severe lordosis, intestinal malrotation, pregnancy, and rapid weight loss.