A nomogram for predicting in-situ inferior vena cava thrombosis following inferior vena cava filter placement in patients with deep vein thrombosis

In-situ inferior vena cava thrombosis (iIVCT) after inferior vena cava filter placement is a clinically relevant complication that may progress to filter-related caval obstruction. This study aimed to develop and internally validate a nomogram for predicting iIVCT in patients with deep vein thrombosis (DVT) who underwent IVC filter placement and follow-up computed tomography venography (CTV). This retrospective single-center study included consecutive patients with DVT who underwent IVC filter placement and both pre-placement and post-placement CTV. Baseline demographics, clinical characteristics, filter-related variables, and CTV-based morphologic parameters were evaluated as candidate predictors. Predictor selection was performed using the least absolute shrinkage and selection operator (LASSO) regression, and the final nomogram was constructed. Discrimination, calibration, and clinical utility were assessed using the area under the receiver operating characteristic curve (AUC), calibration analysis, and decision curve analysis. A total of 113 patients were included, of whom 36 (31.9%) developed iIVCT on follow-up CTV. Five predictors, including cancer, laterality of lower-extremity DVT, age, filter location relative to the renal vein, and minimum IVC diameter magnification percentage, were selected using LASSO regression and incorporated into the nomogram. The model demonstrated an AUC of 0.817 (95% CI, 0.730–0.903), and bootstrap internal validation yielded an AUC of 0.835 (95% CI, 0.750–0.910). Calibration analysis showed acceptable agreement between predicted and observed probabilities, and decision curve analysis suggested potential clinical net benefit across threshold probabilities of 10% to 72%. This exploratory nomogram may help predict the risk of iIVCT among DVT patients undergoing IVC filter placement and follow-up CTV. External validation and further adjustment for anticoagulation-related factors are required before routine clinical application. Not applicable