TRUE MEASURMENT OF INFERIOR VENA CAVA DIAMETER BEFORE FILTER PLACEMENT IS CRUCIAL : CORRELATION BETWEEN THREE METHODS COMMONLY USED
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Accurate determination of inferior vena cava (JVC) size before filter placement is of outmost importance in order to avoid fitter migration espe cially at a diameter of 28 mm (megacava). High quality inferior vena cavaography is mandatory to accomplish this. The purposes of this study were to (a) determine if significant differences exist between JVC meas urements obtained using a gold standard technique and two other widely accepted methods, and (b) if differences exist, how often do these differ ences cause incorrect JVC sizing around a diameter of 28 mm. Twelve inferior vena cavograms were retrospectively evaluated. The transverse diameter of the infrarenal JVC was determined by using a cali brated intravascular catheter (method 1), subtraction of 20% from the measured transverse JVC diameter on a cut-film radiograph (method 2), and a radiopaque ruler placed immediately posterior to the patient (meth od 3), The concordance correlation of methods 2 and 3 versus method 1 were 90.9 % and 81.8% respectively to determine agreement at an JVC di ameter of 28 mm. In conclusion, inferior vena cavegraphy prior to JVC filter placement should be performed with a calibrated intravascular catheter, as the two other formerly accepted methods of determining IVC diameter, that is, the 20% magnification rule, and use of an external measuring device are un reliable and result in high incidence of technically false results.