Overview

FormationL5 (union of common iliac veins)

Caval openingT8, central tendon of diaphragm

Diameter≈2–2.5 cm

Course. The IVC is formed in front of the body of L5, slightly to the right of the midline, where the two common iliac veins join behind the right common iliac artery. It ascends in the retroperitoneum on the right side of the vertebral bodies and the right crus of the diaphragm, to the right of the aorta. It then passes behind the liver in a deep groove on its bare area, where the hepatic veins enter it. It pierces the central tendon of the diaphragm at the caval opening (T8), together with branches of the right phrenic nerve. After a short course in the thorax it enters the lower part of the right atrium.

Valves and breathing. The IVC has no functional valves apart from the rudimentary Eustachian valve at its opening into the atrium. When the diaphragm contracts during inspiration it pulls the caval opening wider, which helps venous return.

Asymmetry of tributaries. The right gonadal and right suprarenal veins drain straight into the IVC. On the left, the corresponding veins drain into the left renal vein, which then crosses in front of the aorta to reach the IVC.

Location: Retroperitoneum and liver bed (L5 to T8), then a short intrathoracic segment that enters the right atrium.

Anatomy

Tributaries: The common iliac veins, the 3rd and 4th lumbar veins, the right gonadal vein, the renal veins, the right suprarenal vein, the inferior phrenic veins and the hepatic veins.
Relations: In front, from below upward: the right common iliac artery, the root of the mesentery, the 3rd part of the duodenum, the head of the pancreas, the bile duct and portal vein, and the liver. The IVC forms the posterior wall of the epiploic foramen. Behind it lie the vertebral bodies, the right crus of the diaphragm, the right sympathetic trunk and the right renal artery.
Development: The IVC is assembled from several embryonic veins: the posterior cardinal, subcardinal, supracardinal and vitelline (hepatic segment) veins. Errors in this process produce anomalies such as a duplicated IVC, a left-sided IVC or an interrupted IVC continuing as the azygos vein.

Function

Returns about two-thirds of total venous return, from the lower body, to the right atrium.

Clinical significance

Aortocaval compression

In late pregnancy, the uterus compresses the IVC when the woman lies on her back. This reduces venous return and can cause supine hypotension. Women are therefore positioned on their left side, or with the uterus displaced to the left during resuscitation.

IVC filter

An IVC filter is inserted below the renal veins to trap emboli from the legs when a patient with venous thromboembolism cannot be anticoagulated.

Tumour thrombus and Budd–Chiari syndrome

Renal cell carcinoma can grow along the renal vein into the IVC, sometimes as far as the right atrium. Obstruction of the hepatic part of the IVC or of the hepatic veins causes Budd–Chiari syndrome.

Mnemonics

IVC tributaries

"I Like To Rise So High": Iliacs, Lumbars, Testicular (right), Renals, Suprarenal (right), Hepatics.

Test yourself

The inferior vena cava passes through the diaphragm at which level?

Answer: T8

The IVC passes through the central tendon at T8. The oesophagus passes through the right crus at T10, and the aorta passes behind the median arcuate ligament at T12. A mnemonic: "I 8 10 Eggs At 12" (IVC 8, oEsophagus 10, Aorta 12).