Radionuclide venography for the demonstration of the proximal deep venous system.

The majority of pulmonary emboli originate in the deep veins of the lower limb. Fatal emboli usually arise from thrombi that have extended into the femoral or iliac veins or lower inferior vena cava. It is often impossible to demonstrate this area, the proximal venous segment, using conventional ascending venography when there is deep venous occlusion. The alternative methods available--retrograde, pertrochanteric and transfemoral venography--are invasive. Radionuclide venography (RNV) has been developed as a less invasive alternative. It has been found to be accurate in the proximal deep venous system when compared with conventional ascending venography, and in the presence of proximal occlusion it gives images unobtainable by other means. The radiation dose is extremely low and a perfusion lung scan is obtained without further injection of isotope. RNV appears to be the best method for monitoring the progress of thrombolytic therapy for major venous occlusion.