Nutcracker syndrome in children - The role of upright position examination and superior mesenteric artery angle measurement in the diagnosis

Objective. The purpose of this study was to evaluate the pathophysiologic characteristics of nutcracker syndrome (NS) and to assess the role of upright position imaging and superior mesenteric artery (SMA) angle measurement in the diagnosis. Methods. Doppler sonographic findings in 23 children with NS and in 26 healthy control subjects were compared. The mesenteric angle, peak velocity (PV), and anteroposterior diameter of the left renal vein (LRV) at the hilar and aortomesenteric portions were measured in both the supine and upright positions. The means +/- SD of the SMA angle, anteroposterior diameter, and PV ratio between the two portions were calculated, and cutoff levels for the diagnosis of NS were established. Results. The diameter and PV ratios were significantly different between the patient and control groups in both the supine and upright positions (P<.001). Differences between the supine and upright positions were also significant for the diameter of the LRV at the aortomesenteric portion, diameter ratio, and SMA angle in both groups. Upright position imaging revealed comparatively narrower SMA angles and more pronounced entrapment findings in patients with NS. The SMA angle measurement had sensitivity and specificity of 69.6% and 61.5%, respectively, in the supine position and 87.0% and 76.9% in the upright position when the cutoff values were set to less than 41 degrees and 21 degrees, respectively. Conclusions. The upright position has significant effects on the LRV hemodynamics and angle of the SMA in both patients and healthy subjects. Superior mesenteric artery angle measurement may be a useful adjunct parameter in the diagnosis of NS.