Anomalous drainage of left renal vein into the azygos venous system without inferior vena cava interruption: a novel anatomic variant

Anomalies of the Left Renal Vein (LRV) are often asymptomatic and found incidentally, but can have major ramifications on both surgical and interventional procedures. We present the case of a 63-year-old male who was incidentally found to have a novel venous anatomic variant, not previously described in the literature. His LRV drains into the azygos venous system up into the chest via the hemiazygos vein, despite the presence of a normal, patent and uninterrupted right-sided Inferior Vena Cava (IVC), and with no communication to the IVC. This configuration differs from known variants that lead to azygous venous drainage such as posterior nutcracker syndrome of a retroaortic left renal vein or azygos continuation of the IVC with congenital interruption. Venous anomalies involving the LRV, including in this patient, may increase the risk of bleeding during retroperitoneal surgery or complicate endovascular procedures involving the left renal, adrenal or gonadal veins. Recognition of variant venous anatomy is key for pre-procedural planning to avoid unnecessary complications.