Corpus: Inferior vena cava

The inferior vena cava is a large-lumen body vein that enters the right atrium from the caudal side. Like the superior vena cava, it is referred to as the "vena cava".

The inferior vena cava is formed by the merging of the right and left common iliac veins at the level of the 4th or 5th lumbar vertebra. This junction is located to the right of the spine and behind the right common iliac artery.

The vein runs behind the peritoneum (retroperitoneally) and to the right of the aorta, ascending diagonally along the posterior abdominal wall toward the central tendon of the diaphragm. Within the liver, it lies in the groove for the vena cava and is anchored there by the ligament of the vena cava. It passes through the opening in the diaphragm known as the caval hiatus (foramen venae cavae) and enters the thoracic cavity. In the thoracic cavity, it courses through the mediastinum along the inner side of the right pleural cavity until it reaches the heart.

Within the pericardium, after a short distance, it empties into the smooth-walled portion of the right atrium known as the sinus venarum cavarum.

• Median sacral vein: This vein drains blood from structures such as the coccygeal glomus and flows either into the junction of the inferior vena cava or the left common iliac vein.
• Right, middle, and left hepatic veins: These veins drain into the inferior vena cava just below the diaphragm. They carry blood from the portal circulation, which includes blood from the stomach, intestines, pancreas, and spleen that has passed through the portal vein.
• Right and left renal veins: The left renal vein typically also collects blood from the left adrenal vein, left testicular or ovarian veins, and the left inferior phrenic vein.
• Right adrenal vein
• Right testicular or ovarian vein
• Right inferior phrenic vein
• Lumbar veins I-IV: These veins drain the posterior abdominal wall.

The inferior vena cava has several short-circuit connections with the superior vena cava, called cavocaval anastomoses.

The inferior vena cava is responsible for transporting deoxygenated blood from the lower half of the body, including the legs, pelvis, and abdominal region, back to the heart.