A critical appraisal of impedance plethysmography in the diagnosis of acute deep venous thrombosis.
Compulsive performance of the test is paramount to obtaining good results. Sequential multiple tests with prolongation of the filling time to maximize venous filling and ultimately reaching a plateau is essential. Increase in venous filling by increasing the cuff pressure in the proximal lower thigh occluding cuff to 60 instead of 45 centimeters of water is helpful in obtaining optimum venous filling. Unrecognized patient apprehension or muscle contraction may be a reason for false-positive IPGs. Patient relaxation, local heat application or even electromyography attachment may be helpful. The IPG can be repeated after a few hours if a false-positive test result is suspected. If a test falls above the stop line, the NPV is so high that no repetition of the test is necessary and the limb is read out as showing no proximal venous thrombosis. If a test is normal or borderline, the test may be repeated with sequential testing until the test points seem to group together or a clear divergence of either normal or abnormal is achieved. If the contralateral limb is clearly normal and an abnormal test result is obtained in the suspected limb, the test is likely to be reliable. Bilateral abnormal IPGs, especially in the presence of congestive heart failure or severe edema, may indicate a false-positive test finding. Increased edema in the extremity decreases electrical resistivity and balancing the machine may become a technical problem.(ABSTRACT TRUNCATED AT 250 WORDS)
D006801:Humans; D008875:Middle Aged; D010992:Plethysmography, Impedance; D011859:Radiography; D013924:Thrombophlebitis / Q000175:diagnosis* / Q000000981:diagnostic imaging