Renal vessels exhibit a high degree of anatomical variations in terms of their number, level of origin, diameter and topographical relationships. In particular, it applies to the left renal vein which can take retroaortic or even circumaortic placement. Anatomical variations of the left renal vein may be of great clinical significance, particularly in the case of renal transplantation, retroperitoneal surgery as well as vascular or diagnostic procedures. Thus, the aim of this report was to present a complete anatomical description of two cases of the circumaortic left renal vein (CLRV; circumaortic renal collar) co-existing with the presence of various vascular anomalies. In the first case, the circumaortic renal collar was connected via a large anastomosis with the hemiazygos vein and was associated with the presence of the supernumerary left renal artery located below the main left renal artery. In the second case, the circumaortic renal collar was accompanied by the renal artery dividing close to its origin. Moreover, in the latter case, the fusiform aneurysm of the abdominal aorta was observed. In both cases, the CLRV began as a single and short trunk. On its further course, the initial segment of the CLRV was divided into two limbs — anterior (anterior left renal vein) and posterior (posterior left renal vein). Both anterior and posterior limb of the CLRV opened into the inferior vena cava.
