Nutcracker syndrome: how are we cracking the nuts and whose nuts are we cracking?

The Nutcracker phenomenon refers to the compression of the left renal vein between the superior mesenteric artery and the aorta, and is often asymptomatic. It is not uncommon, and can be found in up to 10.9%-14% of asymptomatic adults (1, 2) and 33% of children with hematuria (3). The Nutcracker syndrome (NCS) comprises symptoms and findings such as varicocele, ovarian vein syndrome, hematuria, proteinuria and flank pain. Computed tomography and magnetic resonance imaging can demonstrate the anatomic abnormality, and Doppler ultrasonography can help to measure pressure gradient and diameter differences between the left renal vein at the hilum and at the aortomesenteric level. Phlebography might be of value when there are doubts (4). Treatments include clinical management in most cases, and weight gain might be of benefit (5). Nephrectomy, reno-caval re-implantation or shunts (open, laparoscopic or robotic), external stents (open, laparoscopic or robotic) and endovascular venous stents have also been reported (4, 6, 7). Since surgical alternatives are invasive and outcomes are not outstanding (8), endovascular stents have emerged with the appeal of a less invasive procedure. However, some statements have to be reinforced. First, as procedures seems less invasive, there is an apparent increment in the number of indications. We have been seeing a significant increase in the number of cases of tomographic diagnosis of Nutcracker phenomenon. More than that, a significant number of patients have been treated with venous stents, even in cases of doubtful indications. The Nutcracker syndrome is a benign and in most cases self-limited condition, that occurs almost commonly in young patients (resolve with time) (5). Treatment is reserved only for the severe cases. Additionally, venous stents are currently poorly understood. Distinctively from the large acquired experience with arterial stenting, there is relatively little experience and no long term studies with venous stenting. A crucial difference between arterial and chronic venous disease is that the latter seldom poses a threat to life. The venous system might be particularly prone to some severe complications. Fibromuscular hyperplasia, which can lead to vascular occlusion, seems to be more common in veins than in arteries. Proximal embolization can occur, as had the experience with vena cava filter demonstrated (9). Experience with inferior vena cava filters have demonstrated that there is a significant risk of long term complications including IVC thrombosis, perforation, penetration of adjacent viscera, device migration and deep vein thrombosis. These complications get more common according to dwell time (9). For these reason, temporary devices have been developed (9). Additionally, curVol. 43 (4): 788-790, July August, 2017