Multi-positional ultrasonographic assessment of clinically suspected pediatric nutcracker syndrome

Purpose: This study aimed to characterize position-dependent variations in the left renal vein (LRV) in children with suspected nutcracker syndrome (NCS) across supine, standing, and bilateral lateral decubitus positions.Methods: This retrospective observational study included 67 children with clinically suspected NCS, with a median age of 10.0 years.LRV diameters were measured in the supine, standing, left lateral decubitus (LLD), and right lateral decubitus (RLD) positions, and peak systolic velocities were measured in the supine and standing positions.Diameter ratios (hilar/stenotic) were calculated, and the associations of demographic and clinical characteristics with position-dependent anatomical changes were analyzed.Results: The median diameter ratio was highest in the supine position (4.4).Compared with the supine baseline, the diameter ratio decreased significantly in the LLD (3.3) and RLD (3.1) positions (both P<0.001), whereas the decrease in the standing position (4.0) was not statistically significant.Velocity and diameter ratios were positively correlated in both the supine (Spearman rho=0.539,P<0.001) and standing positions (Spearman rho=0.432,P<0.001).Lateral positioning reduced the prevalence of abnormal diameter ratios (>4.0) from 62.7% in the supine position to 31.3% in the LLD position and 23.9% in the RLD position, with no significant difference between the two lateral positions.Male patients had a significantly greater reduction in diameter ratio in the RLD position than female patients (P=0.021).Conclusion: Lateral decubitus positioning provided significant anatomical alleviation of LRV compression compared with the supine baseline in children with clinically suspected NCS.The LLD and RLD positions provided comparable morphological decompression.Comprehensive multi-positional assessment is needed to capture dynamic LRV variation and may provide an objective anatomical basis for considering postural adjustments during conservative observation.