Extent of leg vein thrombosis determined by impedance and 125-I fibrinogen.

Modification of impedance plethysmography to include a thigh cuff improves sensitivity. Twenty-seven of thirty-two subjects (85 per cent) were correctly classified by comparison with phlebograms. Combined surveillance of patients at risk with cuff impedance plethysmography and 125I fibrinogen, carried out fifty subjects after total hip replacement demonstrated that silent venous thrombosis can be detected. Moreover, an estimate of thrombus size can be made, at least to the extent that clinically significant thrombi can be distinguished from minute thrombi.