Clinical significance and renal haemodynamics of incidentally detected retroaortic left renal vein: assessment with venous Doppler sonography.

The purpose of this study was to determine whether renal venous pulsations are affected by compression of the left renal vein (LRV) between the aorta and spine, and also to determine the clinical significance of incidentally detected retroaortic LRV. The study population was recruited from 783 consecutive patients undergoing abdominal CT examination for various indications. 22 patients with a retroaortic LRV were prospectively enrolled in this study, and 22 patients without renal disease served as a control group. After measuring the diameters of the central and peripheral portions of the LRV on CT images, the ratio (P/C) and difference (P-C) of the diameters were calculated. Doppler sonography of the interlobar arteries and veins of the left kidney was then performed to obtain impedance indices. Urine analysis of all subjects and scrotal colour Doppler ultrasound of male patients were also performed. The retroaortic LRV diameters were significantly narrower than the pre-aortic LRV diameters (p = 0.002). The left intrarenal venous impedance indices were significantly higher in the patients with retroaortic LRV (p = 0.026) and in the subgroups with P/C>2 (p = 0.020), with P-C>4 mm (p = 0.007) and without nutcracker-like associations (p = 0.006) than in control subjects, but no significant difference was noted between the arterial resistance indices. Haematuria (n = 8), proteinuria (n = 4), varicocele (n = 3) and collaterals (n = 1) were detected in the study group but not in the control group. In conclusion, incidentally detected retroaortic LRV appears to be associated with haematuria, proteinuria, varicocele and altered venous pulsatility. Further investigations are needed to understand the role of venous Doppler ultrasound in the nutcracker phenomenon.