Inferior vena cava (thoracic part)

At a glance

English

Inferior vena cava (thoracic part)

Latin (TA2)

Vena cava inferior (part thoracica)

System

Vein

Region

Trunk

Side

Single, on the midline

About the inferior vena cava (thoracic part)

Above the diaphragm the inferior vena cava is only a centimetre or two long, yet every drop of venous blood returning from the lower body passes through it. It begins where the vessel leaves the caval opening in the central tendon of the diaphragm, at about the level of the eighth thoracic vertebra, and it ends almost at once by opening into the lower, posterior part of the right atrium. Together with the superior vena cava and the coronary sinus, it is one of the three main inflow channels of the right atrium.

Here the vessel is partly covered by fibrous and serous pericardium; for most of its tiny course it lies within the pericardial sac, behind and below the heart. To its right lies the right pleura and lung, with the right phrenic nerve close by, and behind it lies the oesophagus a little to the left. The caval opening itself is fixed to the vein wall, so when the diaphragm contracts during breathing in, the opening widens and the cava is pulled open, helping venous return.

At its opening into the atrium sits the Eustachian valve: a crescent-shaped fold of endocardium in front of the orifice. Before birth it guides oxygenated blood from the inferior vena cava across the atrium towards the oval foramen. In the adult it is usually small, little more than a ridge, or has disappeared. The orifice lies close to the opening of the coronary sinus, which sits between it and the tricuspid valve.

Clinically, this segment is where catheters and pacing leads passed up from the femoral vein enter the heart. Surgeons place a cannula here for cardiopulmonary bypass, and liver transplant and tumour operations may require control of the cava just above the diaphragm. Tumour thrombus from a kidney cancer sometimes grows up the cava into this part and the right atrium. In rare anomalies the hepatic segment of the cava is absent and the lower body drains through the azygos system, leaving this part carrying only hepatic venous blood.

Course and drainage

Begins at

Continues the abdominal inferior vena cava as it passes through the caval opening of the diaphragm at about T8.

Drains into

Opens into the lower posterior part of the right atrium, the orifice partly guarded by the Eustachian valve.

Drains

Delivers venous blood from the lower limbs, pelvis, abdomen and liver into the right atrium.