Duplex examination of the inferior vena cava.

Duplex examination of the inferior vena cava (IVC) was performed in 270 patients from 1/1/96 to 1/1/00 to define suitability of the IVC for caval interruption using noninvasive means. The IVC was interrogated using a 3-mHz curved linear array probe and an ATL Ultramark 9 ultrasound machine (Bothell, WA). Duplex measured IVC dimensions and defined presence of thrombus or anomalies. Of the 270 IVC duplex examinations 10.7 per cent (n = 29) could not be completed because of overlying bowel gas or for other technical reasons. Of the 241 completed studies 4.1 per cent (n = 10) revealed acute or chronic thrombosis of the IVC. The lateral diameter of the IVC was 20.3 +/- 4.4 mm (95% confidence interval 19.8-20.9 mm), whereas the anteroposterior diameter was 12.6 +/- 4.0 mm (95% confidence interval 12.1-13.1 mm). Excluding those with vena cava thrombosis maximum vena cava diameters exceeded 28 mm in only 2.2 per cent (n = 5) of those with technically adequate studies. Apart from the latter megacavas there were no major IVC anomalies detected. For those with incomplete studies body weight was 192 +/- 59 lb versus 169 +/- 38 lb for those with technically adequate studies (P = 0.008). Technically adequate vena cava duplex examinations can be performed in 89 per cent of patients. On the basis of this and one prior study done at this center IVC duplex can define vena cava dimensions and presence of thrombus. Using the standard criteria for IVC filter insertion that require presence of a maximum cava diameter < or = 28 mm and absence of caval thrombus or anomalies, 94 per cent (226 of 241) of those with complete duplex examinations would have been anatomically suitable for standard Greenfield filter insertion based on noninvasive testing.