Inferior vena cava (IVC): course, tributaries and variants, with the superior vena cava

What it is

The inferior vena cava is the largest vein in the body and returns blood from the lower body to the right atrium.

Location

It forms at about L5 by the union of the two common iliac veins, ascends on the right of the aorta, passes through the caval opening in the central tendon of the diaphragm at T8 and enters the right atrium. It receives the lumbar, right gonadal, renal, right suprarenal, inferior phrenic and hepatic veins.

Function

It returns blood from the lower limbs, pelvis and abdomen.

Body system

Cardiovascular · single, midline structure

FMA ID

FMA10951 (Foundational Model of Anatomy)

Key facts

• The left gonadal and left suprarenal veins drain to the left renal vein, which crosses in front of the aorta just below the superior mesenteric artery.
• It has no functional valves apart from a rudimentary fold at its opening into the right atrium (the Eustachian valve).

Clinical relevance

Inferior vena cava filters are used to prevent pulmonary embolism.

The IVC runs entirely behind the peritoneum (retroperitoneal) in the abdomen. It ascends along the right side of the vertebral column, with the abdominal aorta on its left, passes through the caval opening of the diaphragm at T8 and has only a very short course in the thorax before it opens into the right atrium at the inferior cavoatrial junction. (Radiopaedia: Inferior vena cava.)

In the lower abdomen it lies against the bodies of L3 to L5. Higher up it passes through a fossa (groove) on the back of the liver before it reaches the diaphragm, so its upper part is partly embedded in the liver. (Kenhub: Inferior vena cava.)

After passing through the diaphragm it enters the pericardium at about T8 and drains into the lower part of the right atrium, whereas the superior vena cava enters the upper part. (TeachMeAnatomy: Great Vessels of the Heart.)

In front of the IVC, from below upwards, lie the right common iliac artery, the right gonadal vessels, the third part of the duodenum, the head of the pancreas, the common bile duct, the portal vein, the first part of the duodenum, the epiploic foramen and the liver. (Radiopaedia: Inferior vena cava.)

Behind it are the lumbar vertebrae and discs, the anterior longitudinal ligament, the right psoas major, the right sympathetic trunk and coeliac plexus, and the right renal, lumbar, suprarenal and inferior phrenic arteries. The right renal artery therefore passes behind the IVC on its way to the kidney. (Radiopaedia: Inferior vena cava.)

To its left are the abdominal aorta, the caudate lobe of the liver and the right crus of the diaphragm. To its right are the right kidney, the right ureter, the second part of the duodenum and the liver. (Radiopaedia: Inferior vena cava.)

The portal vein lies directly in front of the IVC in the free edge of the lesser omentum, and the two veins are separated only by the epiploic foramen (foramen of Winslow), the opening into the lesser sac. (Radiopaedia: Portal vein.)

The IVC collects the common iliac veins at L5, lumbar veins from L1 to L5, the right gonadal vein at L2, both renal veins and the right suprarenal vein at L1, and the hepatic veins and inferior phrenic veins at T8. (Radiopaedia: Inferior vena cava.)

The two sides are not symmetrical. The left testicular or ovarian vein and the left suprarenal (adrenal) vein drain into the left renal vein, not into the IVC directly. (TeachMeAnatomy: Venous Drainage of the Abdomen.)

The left renal vein reaches the IVC by crossing in front of the aorta, in the angle between the aorta and the superior mesenteric artery, together with the uncinate process of the pancreas and the third part of the duodenum. (Radiopaedia: Abdominal aorta.)

Blood from the stomach, spleen, pancreas and intestines does not enter the IVC directly. It goes first through the hepatic portal vein to the liver and reaches the IVC through the hepatic veins. (Kenhub: Inferior vena cava.)

The IVC is built from several embryonic veins, so it is described in four segments. The hepatic segment comes from the vitelline veins, the suprarenal (infrahepatic) segment from the right subcardinal vein, the renal segment from anastomoses between the subcardinal and supracardinal veins, and the infrarenal segment from the right supracardinal vein. (Li SJ, Lee J, Hall J, Sutherland TR. The inferior vena cava: anatomical variants and acquired pathologies. Insights Imaging. 2021.)

Radiopaedia adds that the lowest part of the IVC, where it divides into the common iliac veins, comes from the right posterior cardinal vein. Because so many embryonic channels must persist or regress in the right order, the IVC has many variants. (Radiopaedia: Inferior vena cava.)

A duplicated IVC has a prevalence of about 0.2 to 3%. A left-sided IVC is found in about 0.2 to 0.5% of people and results from regression of the right supracardinal vein with persistence of the left. (Li SJ, Lee J, Hall J, Sutherland TR. The inferior vena cava: anatomical variants and acquired pathologies. Insights Imaging. 2021.)

In interrupted IVC with azygos continuation (prevalence about 0.6%), the IVC is interrupted and blood from the lower body reaches the heart through the azygos vein instead. These variants matter in practice: if a duplicated IVC is not recognised, pulmonary embolism can recur despite a routine infrarenal IVC filter. (Li SJ, Lee J, Hall J, Sutherland TR. The inferior vena cava: anatomical variants and acquired pathologies. Insights Imaging. 2021.)

Radiopaedia also lists an absent IVC, a circumcaval (retrocaval) ureter that passes behind the IVC, a circumaortic venous collar around the aorta and IVC webs. (Radiopaedia: Inferior vena cava.)

IVC thrombosis is usually a clot that has spread up from the deep veins of the legs; it rarely starts in the IVC itself. It causes pain and swelling of the legs and scrotum and is treated with anticoagulants, clot-dissolving drugs or surgery to prevent pulmonary embolism. (Kenhub: Inferior vena cava.)

An IVC filter is a small device placed through a vein to catch clots before they reach the lungs, in people who cannot take anticoagulants or who have a pulmonary embolism despite them. It is typically placed in the infrarenal IVC, below the renal veins; suprarenal placement is kept for special cases such as pregnancy. (Radiopaedia: Inferior vena cava filter.)

Renal cell carcinoma can grow along the renal vein into the IVC as a tumour thrombus, and the higher it extends the worse the long-term survival. Blockage of the hepatic veins or the hepatic part of the IVC causes Budd-Chiari syndrome. (Li SJ, Lee J, Hall J, Sutherland TR. The inferior vena cava: anatomical variants and acquired pathologies. Insights Imaging. 2021.)

When the IVC is blocked, blood finds other routes to the heart: collateral veins open through the azygos vein, the lumbar veins and the vertebral venous plexuses into the superior vena cava. (Kenhub: Inferior vena cava.)

The superior vena cava is formed by the union of the right and left brachiocephalic veins, each of which collects the subclavian, internal and external jugular, vertebral and internal thoracic veins of its side. (OpenStax Anatomy and Physiology 2e, 20.5: Circulatory Pathways.)

It begins behind the lower border of the first right costal cartilage, descends vertically behind the first and second intercostal spaces and drains into the right atrium at the superior cavoatrial junction, behind the right third costal cartilage. Its only large tributary is the azygos vein, which joins it from behind. (Radiopaedia: Superior vena cava.)

The azygos vein begins in the upper abdomen, collects the intercostal, oesophageal (esophageal) and bronchial veins and flows into the superior vena cava. (OpenStax Anatomy and Physiology 2e, 20.5: Circulatory Pathways.)

The SVC has the ascending aorta and arch on its left, the right lung, pleura and right phrenic nerve on its right, and the right main bronchus and azygos vein behind. Variants include a left-sided or duplicated SVC and right upper lobe pulmonary veins draining into it. (Radiopaedia: Superior vena cava.)

Superior vena cava obstruction is caused by cancer in about 70% of cases, mainly lung cancer and lymphoma; the rest are benign, for example from central venous catheters and pacemaker wires. Acute obstruction causes swelling and flushing of the face and neck and swelling of both arms, worse when lying flat. (Radiopaedia: Superior vena cava obstruction.)

The nearest named structures in the 3D model, measured from the centre of each part:

• Celiac artery · cardiovascular
• Celiac trunk · cardiovascular
• Common hepatic duct · digestive
• Common hepatic artery · cardiovascular
• Diaphragm · muscular
• Trunk of gastroduodenal artery · cardiovascular
• Hepatic portal vein · cardiovascular
• Pre-hepatic portal vein · cardiovascular
• Cystic duct · digestive
• Posterior superior pancreaticoduodenal artery · cardiovascular