Anatomical variants of the retroaortic left renal vein

Background: Anatomical variants of the left renal vein (LRV), such as the retroaortic (RLRV) and circumaortic (CLRV) course, are of surgical importance. Different morphological and topographical possibilities of the RLRV could occur. It was aimed at documenting the anatomical variables of the RLRV.Method: A retrospective study on 375 computed tomography angiograms was performed. Five different anatomical types of LRV were documented: preaortic types 1 and 2 and retroaortic types 3-5.Results: In 344/375 cases, preaortic LRVs were found. In 31/375 cases, different types of RLRV were found: type 3a - single RLRV, 41.94%; type 3b - single RLRV with bifid caval end, 9.68%; type 3c - single RLRV with trifid caval end, 3.23%; type 4a - CLRV with extrahilar origin, 29.03%; type 4b - CLRV with renal sinus origin, 12.9%; type 5 - triple LRV (one preaortic LRV and two RLRVs), 3.23%. Reference vertebral levels were recorded for the prevertebral segment of the RLVR. The vertebral level of type 3a varied from the L1/L2 disc to the upper third of the L4 vertebra. Type 3b was found in 3/31 RLRV cases; in one of these, the hemiazygos vein was inserted by two roots into the LRV and its upper caval end trunk. There was a significant statistical association between type 3b and the vertebral level, all cases being centered on the middle third of the L4 vertebra.Conclusions: New morphological possibilities of the LRV were distinguished, and a new anatomical classification system of the RLRV results. The RLRV variant should be documented case-by-case as it has its anatomical variables.