[Doppler pulsed and color echography of the inferior vena cava].

Abstract

B mode real time echotomography associated with duplex and colour doppler makes possible a complete investigation of the lower vena cava. The ilio-cava fossa is difficult to explore because of gas and digestive superpositions. Diagramatically, it is possible to distinguish five levels of investigation. 1) Iliac veins and ilio-cava convergence. 2) Sub-renal LVC. 3) Inter-renal LVC and communications with renal veins. 4) Retro-hepatic LVC: communications with liver and supra-hepatic veins. 5) Thoracic LVC and termination in the right atrium. Sector-based probes provide a 60 to 110 degrees sector thanks to which it is possible to obtain a sufficient exploration field for a very limited acoustic fenestra. Duplex and colour doppler assess the venous flow and its variations during the respiratory cycle and during the operations of compression or Valsalva's experiment. Colour doppler detects more precisely slow, collateral or repermeation flows. The recent complete thrombosis leads no duplex and colour doppler signal but an increase of the vein diameter associated with a collateralitis syndrome. In case of partial thrombosis, the vein is partially compressible as colour doppler fits thrombus closely round and visualizes the remaining lumen. In the ilio-cava fossa, compressions (either tumorous, ganglial or aneurysmal) which are often associated are diagnosed in the meanwhile. It is important to know the change of diameter and the abnormalities of the LVC position when a cava blocking is advised. A LVC whose diameters exceed 28 mm (mega-cava) contra indicated filter because of the risk of migration. Colour doppler makes easier the supervision of the blocking.