Tributaries of the Inferior Vena Cava
The inferior vena cava, the largest vein in the human body, transports blood from the lower limbs, most of the back, the abdominopelvic viscera and the abdominal walls to the right atrium. It is formed by the union of the common iliac veins at the level of the body of L5. During its course, it receives many veins referred to as tributaries of the inferior vena cava. This article will discuss the anatomy of these tributaries in detail, followed by any relevant clinical notes.
Apart from the common iliac veins, there are 6 pairs of veins, 2 singular veins and a hepatic group of veins, which drain into the inferior cava directly. They include:
- Four pairs of lumbar veins
- The right gonadal vein
- A pair of renal veins
- The right suprarenal vein
- A pair of inferior phrenic veins
- A group of hepatic veins
The lumbar veins drain blood from various areas of the body via many tributaries. Dorsal tributaries drain blood from the lumbar back and skin whereas abdominal tributaries drain blood from the anterior, posterior and lateral abdominal walls as well as from the parietal peritoneum. The lumbar veins collect blood from the vertebral plexuses near the vertebral column. Here, they are connected by the ascending lumbar vein, which runs anterior to the transverse processes of the lumbar vertebrae.
The third and fourth lumbar veins usually enter the posterior aspect of the inferior vena cava but the first and second lumbar veins are more variable. The first lumbar vein occasionally drains into the inferior vena cava but usually drains into the second lumbar vein, the ascending lumbar vein or the azygos vein. At the level of the renal veins, the second lumbar vein usually joins the inferior vena cava but it may occasionally drain into the third lumbar vein or the ascending lumbar vein.
The right gonadal vein (ovarian in females and testicular in males) joins the inferior vena cava just inferior to the level of the left renal vein at an acute angle. It opens into its right anterolateral aspect and is usually double in its course.
The renal veins open into the inferior vena cava almost at right angles and lie anterior to the renal arteries. The right renal vein is 2.5 cm long and is found posterior to the second part of the duodenum. The left renal vein, at 7.5 cm, is three times the length of its right counterpart and lies on the posterior abdominal wall. It is located posterior to the splenic vein and the body of the pancreas. Close to the inferior vena cava, it is found anterior to the aorta and inferior to the superior mesenteric artery.
At the level of the T12, the right suprarenal vein drains into the inferior vena cava.
The inferior phrenic veins drain into the posterolateral aspect of the inferior vena cava at the level of T10. The left inferior phrenic vein drains higher than its right counterpart and is found superior to the oesophageal opening in the diaphragm. It may be double and has a branch, which drains into the left suprarenal or renal vein.
Three main hepatic veins and some minor hepatic veins drain the liver and join the inferior vena cava. The first main vein is the longest, most variable vein and is referred to as the right hepatic vein. The liver can be divided into 9 segments and the right hepatic vein drains segments VI and VII as well as parts of segments V and VIII. It is formed near the anteroinferior aspect of the liver and enters the inferior vena cava near the upper border of the caudate lobe. The other two main veins, the middle and left hepatic veins, usually drain into the inferior vena cava as a common trunk. The middle hepatic vein usually drains segments IV, V and VIII, whilst the left hepatic vein drains segments II and III as well as segment IV on occasion. Minor veins which drain segment I also enter directly into the inferior vena cava.
The common iliac veins join at the level of L5 to form the inferior vena cava and can thus be considered its tributaries of origin.