Appropriate placement of an inferior vena cava (IVC) filter necessitates imaging of the renal veins and characterization of their number and their confluence with the IVC. Imaging is desirable during filter placement to ensure that when an IVC filter is deployed, its tip is at or below the inferior aspect of the confluence of the inferiormost renal vein with the IVC. Placement of an IVC filter above the renal veins can lead to thrombosis of the renal veins if an embolus is caught by the filter. Placement of the filter too far below the renal veins creates a dead space in the IVC above the IVC filter if an embolus is caught. A second thrombus can then form above the filter and subsequently embolize to the lungs. Classically, imaging during placement of IVC filters is with conventional inferior vena cavography and fluoroscopy.
2-4Keywords ► inferior vena cava ► computed tomography ► filterplacementguidance ► deep vein thrombosis ► obesity
AbstractAppropriate placement of an inferior vena cava (IVC) filter necessitates imaging of the renal veins because when an IVC filter is deployed its tip should be at or below the inferior aspect of the inferiormost renal vein. Traditionally, imaging during placement of IVC filters has been with conventional cavography and fluoroscopy. Recently, intravascular ultrasound has been used for the same purpose but with additional expense. Morbidly obese patients often exceed the weight limit of fluoroscopy tables. In addition, short obese patients are at risk of falling from narrow fluoroscopy tables. For such patients, computed tomography (CT) guidance is a viable alternative to conventional fluoroscopic guidance. IVC placement was performed in the CT suite for two obese patients who exceeded the weight limits of the available fluoroscopy tables. In one case, a Vena-Tech filter (Braun Medical, Melsungen, Germany) was placed using CT fluoroscopy. In the second case, a Recovery (Bard, Murray Hill, NJ) filter was placed using intermittent limited z-axis scanning. In the first case, the filter was placed below the level of the renal veins and above the confluence of the iliac veins, which is acceptable placement. In the second case, with refinement of technique, the filter tip was placed less than 1 cm below the inferiormost renal vein, which is considered optimal placement. CT of the IVC precisely images the renal veins and can characterize their number and their confluence with the IVC. CT guidance is a viable alternative to fluoroscopic guidance for the placement of IVC filters in morbidly obese patients.