The inferior vena cava (IVC) is a retroperitoneal structure which arises dorsally to the right common iliac artery from the junction of the right and left common iliac veins. It ascends posterior to the right gonadal artery, the transverse colon, mesenteric root, pancreas and duodenum to reach the sulcus venae cavae on the posterior surface of the liver. It then penetrates the diaphragm to enter the right atrium. The common iliac veins, lumbar veins, right gonadal vein, renal veins, right adrenal vein, phrenic vein and hepatic veins drain into the IVC. Congenital anomalies of the IVC occur in less

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Fig. 6a, b. Two-dimensional (2D) TOF MR venography at (a) the level of the inferior vena cava and (b) femoral vein. Thrombus (arrows) in the inferior vena cava and right femoral vein appearing with dark signal intensity is well depicted

than 1% of cases although the incidence is higher in patients with congenital heart disease. A left-sided IVC is the commonest of these anomalies. In these patients the left-sided IVC terminates in the left renal vein, which then usually drains into a normally located distal segment of the IVC. A double IVC is a less frequent finding. The left vena cava again usually terminates in the left renal vein but may occasionally drain into the lumbar and hemiazygos venous system, the coronary sinus or the left atrium. The suprarenal segment of a normal or abnormal IVC may occasionally drain into the azygos and hemiazygos vein instead of passing through the liver. In the presence of agenesis or hypoplasia of the IVC, blood from the pelvis and lower extremities drains mainly into the lumbar, hemiazygos and azygos veins, which act as collateral vessels.

The venous drainage of the lower limbs can be anatomically categorized into two separate systems - the superficial and deep systems. The deep veins usually follow the course of the main arteries. In the lower extremity, the deep venous system includes the superficial and deep femoral veins, the popliteal vein, and the anterior tibial, posterior tibial, and peroneal veins. The veins are commonly paired at the tibial level, and may, as normal variants, be duplicated at the popliteal and femoral levels as well. The deep femoral vein, which usually lies in the upper two-thirds of the calf, may connect with its lower part and with the superficial femoral or popliteal veins.

The greater saphenous vein is the longest superficial vein. It runs from the dorsal arch of the foot medial to the tibia up the medial thigh to the femoral vein. The lesser saphenous vein runs from the lateral arch of the foot postero-laterally in the calf to join the popliteal vein. Beyond being used as graft vessels for arterial bypass procedures, the superficial venous system is an important collateral pathway in the event of DVT.

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Essentials of Human Physiology

Essentials of Human Physiology

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