Anatomical variants of circumaortic left renal vein

The circumaortic left renal vein (CLRV) is a critical retroperitoneal vascular variant. Current classification systems frequently omit possible morphologies. This study aims to delineate intricate CLRV patterns and propose a preliminary classification framework. Contrast-enhanced abdominal computed tomography (CT) scans of 380 adult patients (199 males and 181 females, with a mean age of 63.8±15.1 years) were retrospectively evaluated using multiplanar and three-dimensional volume-rendered reconstructions. CLRV variants were categorized into four groups: Type A (bifurcation), Type B (independent double veins), Type C (single interconnection close to the hilum), and Type D (double interconnection). Seventeen CLRV cases were identified, demonstrating a prevalence of 4.5% (10 females, 7 males). Type A was observed in 8 cases (2.1%), Type B in 2 cases (0.5%), Type C in 6 cases (1.6%), and Type D in 1 case (0.3%). The unique Type D configuration featured a double anastomosis with a renal artery passing between the interconnections. A statistically significant association was found between the morphological type and vertebral span (P=0.002), where interconnected variants (Types C and D) exhibited a significantly narrower span (0.9±0.1 vertebrae) than non-interconnected types (1.8±0.8 vertebrae); however, this finding must be interpreted cautiously due to the small subgroup sizes. This novel classification system successfully bridges a literature gap by accounting for complex configurations, offering an exploratory anatomical map to enhance safety during retroperitoneal surgeries and renal transplantations.