Ultrasound Diagnosis of Left Renal Vein Entrapment (Nutcracker Syndrome)

bmccleary's picture
Brendan McCleary (1), Oleg Mironov (2)
(1) MS4 (2) MD
(1) University of Rochester School of Medicine (2) University of Rochester Medical Center

Figure Legends : 

In the transverse view of this patient, the superior mesenteric artery can be seen in overlying the left renal vein, which is in turn compressed as it passes over the aorta. At this point there is also velocity elevation from 10 cm/sec to 170 cm/sec. By diameter criteria, this patient has a 5.3 to 1 ratio of renal hilar to proximal LRV diameter, and meets the diagnosis of LRV entrapment. However, if a velocity ratio is calculated for the same points in the vessel, the patient easily surpasses the diagnostic bar, with a ratio of approximately 17:1.

Case Description

Clinical History: 

19 year-old male with gross hematuria for several years who gradually became anemic. Evaluate for left renal vein compression and possible arterio-venous malformation.


Left renal vein entrapment by the superior mesenteric artery


The left renal vein entrapment syndrome, commonly known as the “nutcracker syndrome” is a rare and probably underdiagnosed condition. The term refers to the compression of the left renal vein between the aorta and the superior mesenteric artery. This results in increased left renal vein pressure and peak velocity, formation of collateral veins and their subsequent rupture into the calyceal fornices and development of hematuria. Patients may also suffer from albuminuria, lumbar/left-flank pain, and men may show varicocele. Women may also experience pelvic varices, chronic pelvic pain, dyspareunia, dysuria or dysmenorrhea. The nutcracker syndrome refers to symptomatic disease, while nutcracker phenomenon simply refers to its radiographic findings in absence of symptoms.

Although other modalities, such as venography and CT angiography are used to diagnose this condition, researchers in the last decade have developed useful criteria for diagnosing nutcracker syndrome with ultrasound. While increased LRV diameter alone is not specific for nutcracker syndrome diagnosis, spectral and doppler ultrasound can provide extra information about flow and velocity. The most useful ultrasound measure of stenosis of the LRV is the ratio of peak systolic flow velocity in the proximal vs hilar portions of the vein. The cutoff for diagnosis is set by various studies at > 3.7-5.0 in children and > 5.0 in adults, allowing near 100% sensitivity and 90% specificity. Venography remains the gold standard for diagnosis of this condition, but CT or MR angiography are the most common follow-up studies after ultrasound diagnosis.

Treatment for LRV entrapment remains controversial. In children with LRV entrapment, one possible recommendation for treatment is the allowance of a gradual increase in BMI that comes with normal development. This theoretically provides increased soft tissue volume to pad the LRV from compression by the SMA. In adults, options include stenting. renocaval reimplantation, SMA transposition, and saphenous vein or synthetic bypass grafting.

References / Suggested Reading: 

  1. Kim, S. H., Cho, S. W., Kim, H. D., Chung, J. W., Park, J. H., & Han, M. C. (1996). Nutcracker syndrome: diagnosis with Doppler US. [Research Support, Non-U.S. Gov't]. Radiology, 198(1), 93-97.
  2. Liebl, R. (2005). Nutcracker phenomenon or nutcracker syndrome? [Comment Letter]. Nephrol Dial Transplant, 20(9), 2009; author reply 2009.
  3. Menard, M. T. (2009). Nutcracker syndrome: when should it be treated and how? [Review]. Perspect Vasc Surg Endovasc Ther, 21(2), 117-124.
  4. Natale, F., Granato, C., Aronne, L., Di Marco, G. M., Lo Priore, E., Mocerino, R., . . . Calabro, R. (2009). Nutcracker syndrome. [Case Reports]. Eur J Echocardiogr, 10(8), 993.
  5. Scultetus, A. H., Villavicencio, J. L., & Gillespie, D. L. (2001). The nutcracker syndrome: its role in the pelvic venous disorders. J Vasc Surg, 34(5), 812-819.
  6. Shin, J. I., Park, J. M., Lee, J. S., & Kim, M. J. (2007). Doppler ultrasonographic indices in diagnosing nutcracker syndrome in children. Pediatr Nephrol, 22(3), 409-413.
  7. Venkatachalam, S., Bumpus, K., Kapadia, S. R., Gray, B., Lyden, S., & Shishehbor, M. H. (2011). The nutcracker syndrome. [Review]. Ann Vasc Surg, 25(8), 1154-1164.
  8. Zhang, H., Li, M., Jin, W., San, P., Xu, P., & Pan, S. (2007). The left renal entrapment syndrome: diagnosis and treatment. Ann Vasc Surg, 21(2), 198-203.


Ultrasound Diagnosis of Left Renal Vein Entrapment (Nutcracker Syndrome), Brendan McCleary (1), Oleg Mironov (2), Imaging Science Today, 2012, 4396.