Renal vein
Vena renalis
The renal veins drain the kidneys into the inferior vena cava. The left renal vein is about three times longer than the right. It crosses in front of the aorta, just below the origin of the superior mesenteric artery.
Overview
At the renal hilum the renal vein lies in front of the renal artery.
The right renal vein is short, about 2.5 cm, and drains straight into the IVC. The left renal vein is about 7.5 cm long. It passes in front of the aorta, in the angle between the aorta and the superior mesenteric artery, to reach the IVC. On the way it receives the left gonadal vein, the left suprarenal vein and often the left inferior phrenic and a lumbar vein. This asymmetry exists because the IVC lies to the right of the midline.
Anatomy
- Tributaries
Both renal veins receive interlobar veins from inside the kidney. The left renal vein also receives the left gonadal, left suprarenal, left inferior phrenic and second lumbar veins.
Function
- Return filtered blood from the kidneys, about 20% of cardiac output, to the IVC.
Clinical significance
Living donor nephrectomy
Surgeons usually take the left kidney from living donors, because the longer left renal vein makes the transplant connection easier.
Nutcracker syndrome
The left renal vein can be squeezed between the aorta and the SMA. This causes blood in the urine, left flank pain, a left varicocele or pelvic congestion.
Renal vein thrombosis and tumour extension
Renal vein thrombosis complicates nephrotic syndrome, especially membranous nephropathy, partly because antithrombin is lost in the urine. Renal cell carcinoma can grow into the renal vein and the IVC. When it blocks the left gonadal vein, it can cause a new left varicocele that does not empty when the patient lies down.
Test yourself
The left testicular vein usually drains into the:
- Inferior vena cava
- Left renal vein
- Left common iliac vein
- Left internal iliac vein
Answer: Left renal vein
The left gonadal vein joins the left renal vein at a right angle, while the right gonadal vein joins the IVC directly. This asymmetry is one reason why about 90% of varicoceles are on the left.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.