The diameter of the inferior vena cava and its implications for the use of vena caval filters.

Inferior vena caval diameters were measured in 65 patients with Kimray-Greenfield (KG) inferior vena caval filters. The measurements were made at the distal tips of the filter tines on postplacement radiographs. Magnification corrections were made using the filter tine lengths as references. The overall mean diameter was 20 mm, the range was 13 to 30 mm, and the standard deviation was 3 mm. Two cavae (3%) were more than 28 mm in diameter. A previous in vitro study has shown that in venae cavae of this size there is a significant risk of reduced clot-capturing ability with the KG filter and migration with the Mobin-Uddin filter. Thus it is important to evaluate vena caval diameter by cavography prior to filter placement.