Evaluation Of Nutcracker Syndrome With Contrast-enhance Magnetic Resonance Angiography (CE-MRA)

Objective: To assess diagnosis of nutcracker syndrome with contrast-enhanced magnetic resonance angiography. Methods: We studied 31 patients of nutcracker syndrome and 36 volunteers as control by contrast-enhanced 3D magnetic resonance angiography (MRA). We measured the angle (a) of the origin of the superior mesenteric artery(SMA) from the abdominal aorta(AO), and the distance (a) of the origin of the SMA before it began a caudal descent in the sagittal plane that crossed the AO and SMA, the distance (b) between the SMA and aorta in the axial plane crossing the left renal vein(LRV), and we measured the supero-inferior diameter (c) of LRV left lateral to the aorta, and we also measured the macroaxis(d) of the left renal.Results: There were 2 posterior- nutcracker syndrome, in which the LRV crossed into IVC behind aorta. Of the anterior- nutcracker syndrome, the angle of the origin of the superior mesenteric artery(SMA) from the abdominal aorta(AO), the distance between the SMA and aorta in the axial plane crossing the left renal vein(LRV) and the supero-inferior diameter ofLRV left lateral to the aorta were 27.8±8.2° , 4.2±1.3mm, 14.9±2.3mm in patients, and 81.7±13.4° ,16.1±6.8mm,11. 9±2.6mm in control group, respectively. We compared all of these value, and found the three value had the significantly difference between patients group and control group but not so as the distance of the origin of the SMA before it began a caudal descent and the macroaxis of the left renal. But there is an overlap of the supero-inferior diameter of LRV between two groups. We set the cutoff value of the angle of SMA and AO (α)<45 ° and the distance between SMA and AO (b) <6.5mm, and found the sensitivity and specificity is 89.7% and 100% respectively.Conclusion: MRI is good at diagnosing the nutcracker syndrome, and it is a noninvasive method. Observing in multiple-plane and comparing with measure the angle and distance between the superior mesenteric artery and the aorta will clearly demonstrates the entrapment of LRV between AO and SMA and give a right diagnosis.