Progressive Obstruction of Inferior Vena Cava by Ameroid Constrictor: The Canine Model of Revealing Hemodynamic and Compensatory Patterns of Tumor Thrombus Formation at the Renal Hilus Level

Background: To develop an efficient and stable canine model of inferior vena cava (IVC) progressive obstruction at the renal hilus level. Methods: The model was established in two beagles by encircling an ameroid constrictor (AC) on the IVC at the renal hilus level. Abdominal wall varicosity and animal weight variations were observed weekly after operation. Ultrasound examination was performed weekly after surgery to observe the AC position, the diameter, and the velocity in the IVC. Six weeks after surgery, IVC angiography and CT scan were performed to observe the collateral circulation establishment and internal organ variation. Blood samples were taken regularly to monitor for variation in critical biochemical parameters. Renal biopsy was performed at 0, 2, 4, and 6 weeks after surgery. Results: Superficial varicose veins were observed on the abdominal wall at 2 weeks after surgery. Four weeks after operation, the IVC diameter increased by ∼30%, whereas the IVC velocity decreased by more than 50%. Collateral circulation was observed by IVC angiography at 6 weeks through multiple dilated veins along with neovascularization. CT scan showed congestive alteration in the kidney. The body weight, kidney, and liver function were not significantly affected. Chronic congestive renal injury was detected in the renal tubular epithelium by kidney biopsy after surgery. Conclusions: A canine model of IVC progressive obstruction at the renal hilus level was stably and safely established for the first time by using an AC, which may be helpful for preserving pivotal collateral circulation and nontumor-side kidney function in the IVC thrombus surgery.