Classification of the renal vein variations: a study with multidetector computed tomography

To estimate the incidence, anatomical feature as well as type of the renal vein variation with multidetector computed tomography (MDCT) in an adult population. A total of 1,452 patients who underwent MDCT angiography were retrospectively evaluated for the presence (number, length, origination, destination, branching pattern and course) of the renal vein variation. chi A(2) test was used to compare the incidence of variations in left and right renal veins and the incidence of variations in each side renal vein between males and females. Renal vein variations were observed in 358 patients (24.7 %, 358/1,452), which included 103 patients (7.1 %, 103/1,452) with left renal vein (LRV) variations, 279 patients (19.2 %, 279/1,452) with right renal vein (RRV) variations and 24 patients (1.7 %, 24/1,452) with bilateral renal vein variations. The frequency of RRV variations was significantly higher than that of LRV variations (p < 0.05). No statistically significant correlation was found between variations of renal vein (LRV and RRV) and gender (p > 0.05). According to the morphology of the renal vein, we classified LRV variations into five types: type I, circumaortic LRV (2.1 %, 31/1,452); type II, retroaortic LRV (2.1 %, 30/1,452); type III, abnormal reflux (1.7 %, 24/1,452); type IV, late venous confluence of LRV (0.9 %, 13/1,452); type V, rare type (0.3 %, 5/1,452), and RRV variations into three types: type 1, additional renal vein (18.7 %, 271/1,452); type 2, abnormal reflux (0.4 %, 6/1,452); type 3, rare type (0.1 %, 2/1,452). The renal vein variations are not unusual, particularly in the RRV. Anomalies of the LRV are more complex than those of the RRV. The renal vein anatomy can be well depicted by MDCT angiography. Our new classification of the renal vein variations will improve the recognition of the renal vein morphology preoperatively.