To discuss the CT findings after inferior vena cava(IVC) filter placement, and their value in evaluating the status of IVC filters after placement and related complications.

Pertinent data of 31 cases with IVC filter placement who underwent abdominal CT plain scan, contrast-enhanced scan and 3D reconstruction from January 2011 to May 2016 was collected for this study. The location, morphology and complications of IVC filters were evaluated on CT images.

(1) CT and 3D reconstruction images can clearly display the IVC filter and determine its type. Among the 31 cases, 12 cases of Ease type (including the retrievable Opt type) showed six-diamond shape, and 6 struts converging at the upper and lower apex of the filter formed the symmetric double baskets, with a retrieval hook in the bottom of OptEase filter; 7 cases of Vena Tech showed a cone shape formed by 6~8radial prongs, with vertical stabilizing struts around; 6 cases of Günther Tulip presented as inverted "tulip" shape, with a hook at the top and 4 struts below; 4 cases of Simon Nitinol presented as overlapping "umbrellas" , with 8 partially overlapping loops forming the top "umbrella" , and 6 diverging legs forming the lower "umbrella" ; 2 cases of temporary retrivable filter Tempofilter II showed long-arm "umbrella" shape, with 8 struts forming the cone-shaped basket, connected with long retrieval handle located in the course from internal jugular vein to inferior vena cava. (2) In 28 cases the filters were located in the infrarenal IVC, which was the conventional position, while 3 cases were in the suprarenal IVC, all of which formed suprarenal IVC thrombus before filter placement. (3) 10 cases showed obvious thrombus in the filters and above IVC, 1 of which also showed IVC stenosis, while no thrombus was found in the remaining 21 cases. (4) None of the 31 cases showed rupture of the main body or struts of IVC filters. 1filter migrated to the hepatic IVC and penetrated to liver parenchyma; the other 30 cases were classified into four grades according to IVC filter strut interactions with IVC wall. There were 7 cases classified as Grade 0, 13 cases as Grade 1, 3 cases as Grade 2, and 7 cases as Grade 3 (3 cases penetrating to the aortic wall and lumbar vertebrae, 1 case to the right psoas major and ileum, and 1 each to the aortic wall, anterior lumbar, and right diaphragmatic crura). The filters were significantly tilted in 7 cases, with the angle between the central longitudinal axis of the filter and the IVC being more than 15°, which showed the best result with coronal and sagittal reconstruction.

CT can clearly show the shapes, location and complications of IVC filters, which can provide a good way for retrieval of filters and treatment of complications.