TRANSJUGULAR INTRAHEPATIC PORTOSYSTEMIC SHUNT IN A PORCINE MODEL - HISTOLOGIC CHARACTERISTICS AT THE EARLY-STAGE

Rationale and Objectives. The authors attempted to determine the histo logic processes that take place during development of stenosis after t ransjugular intrahepatic portosystemic shunt (TIPS) creation. Material s and Methods. TIPS were created with metallic stents in 20 healthy do mestic pigs (tantalum stents in 10, stainless steel stents in 10). The animals were sacrificed 2-16 days later. All the shunts were examined by means of venography both immediately after placement of the stents and before sacrifice. All histologic sections were assessed with modi fied Giemsa and basic fuchsin stains. Anti-smooth-muscle-cell alpha-ac tin stain was used in three specimens. The stenotic reaction was quant ified by using standard planimetry techniques and a computerized image -analysis system. Results. Within 16 days after TIPS placement, 15 (75 %) of the 20 shunts were completely occluded, four (20%) of 20 shunts were partially occluded, and one (5%) of 20 shunts remained widely pat ent (animal died of unknown cause 2 days after the TIPS procedure). St ent occlusion was caused primarily by pseudointimal hyperplasia, which ws similar morphologically in the portal, middle, and hepatic portion s of the stent. Myofibroblastic proliferation was the most striking fe ature of the pseudointimal hyperplasia. The average thickness of the p roliferation was 2.14 mm, which was 67% of the total diameter of the s tent. A mild fibrous or lymphocytic reaction occurred around the stent wires adn between the pseudointimal hyperplasia and the liver parench yma. Conclusion. The histologic features of pseudointimal formation in this swine. TIPS model closely resemble those in humans. This model m ay prove useful for evaluating stents and other devices and improving the understanding of restenosis after vascular interventions.