The renal veins drain each kidney into the inferior vena cava at approximately the L1-L2 level. The left renal vein is longer, crossing anterior to the aorta to reach the IVC, and receives the left gonadal, left suprarenal, and left ascending lumbar veins. The right renal vein is shorter and more direct. The left renal vein is a critical landmark in aortic surgery and retroperitoneal dissection.
The left renal vein crossing the aorta at the level of the SMA can be compressed between the aorta and the superior mesenteric artery, producing nutcracker syndrome with haematuria, left flank pain, and left gonadal vein engorgement causing varicocele in males or pelvic congestion syndrome in females. In radical nephrectomy, the renal vein is ligated medially and the renal artery first to reduce renal venous congestion. Renal cell carcinoma with renal vein tumour thrombus extending into the IVC requires en-bloc resection with varying IVC management depending on thrombus level.
Compression of the left renal vein between the aorta and superior mesenteric artery reduces renal venous drainage, producing haematuria, left flank pain, and left-sided varicocele or pelvic congestion from ovarian vein engorgement, managed with endovascular stenting or surgical transposition.
Renal cell carcinoma extension into the renal vein and IVC occurs in up to 10% of cases; thrombus level (Neves classification) determines operative strategy, from simple renal vein control to cardiopulmonary bypass for level IV thrombus reaching the right atrium.
