High occlusion rate in experimental transjugular intrahepatic portosystemic shunt created with a Dacron-covered nitinol stent.

PURPOSE: To assess whether the use of a prosthesis covered by a Dacron sheath might prevent pseudointimal hyperplasia in a transjugular intrahepatic portosystemic shunt (TIPS). MATERIALS AND METHODS: A TIPS procedure was performed in nine pigs, after creation of a portal vein microembolization model of portal hypertension, by using a Dacron-covered nitinol stent. The first centimeter on the lower extremity of this specially made prototype was uncovered, to avoid portal vein thrombosis. Three weeks later, the seven surviving animals underwent transjugular hemodynamic and angiographic follow-up and were then killed for gross and histologic evaluation. RESULTS: Shunt insertion was possible in all pigs; two died of complications of the procedure. After 3 weeks only two shunts were patent, although a 50%-60% narrowing of the initial portion of the shunt was present; the remaining shunts were occluded. Histologic examination showed pseudointimal hyperplasia associated, in the cases of occlusion, with a luminal thrombosis. CONCLUSION: This Dacron-covered stent did not prevent pseudointima formation over the stent and resulted in a high early occlusion rate, probably related to a pronounced tissue fibrotic response likely due to Dacron-induced inflammation.

Histopathologic analysis of transjugular intrahepatic portosystemic shunts.

This prospective study was undertaken in 17 patients treated with 22 transjugular intrahepatic portosystemic shunt (TIPS) procedures and aimed to evaluate the nature and causes of short- and long-term shunt abnormalities. Specimens were collected after autopsy in 6 patients and after liver transplantation in 11 patients; the time from shunting ranging from 4 to 385 days. During the first 2 weeks the shunt surface was covered by poorly organized fibrin platelet clots that were mixed with inflammatory and red blood cells. Thereafter, a pseudointima developed, initially made of loose granulation tissue that was formed by edema, myofibroblasts, neo-capillaries, collagen fibers, and inflammatory cells. This pseudo-intima extended with time as the myofibroblasts increased in number, as the collagen fibers thickened, and as the inflammatory cells grew more scarce. Its thickness ranged from 50 to 3,500 microm, the maximal values being observed in the middle of the shunt. The shunt was obstructed by a clot in 4 patients (18%). In 7 shunts (31.8%) the pseudo-intima was thicker than 1,000 microm and was referred to as hyperplastic pseudo-intima. It showed more dense inflammatory infiltrate and anarchic deposition of more scarce collagen fibers. Pseudo-intima hyperplasia was associated with previously diagnosed thrombosis, which had been treated by dilatation in 2 cases and by biliary deposits in 3 cases, while it remained unexplained in 2 cases. Accordingly, this study confirms the following: 1) that early TIPS obstruction results from thrombosis; 2) that 2 weeks after insertion, the stent is covered by a smooth pseudo-intima; 3) that thereafter, pseudo-intimal hyperplasia is the main cause of TIPS stenosis or occlusion; and 4) that biliary secretions and previous thrombosis could be important triggering mechanisms for this pseudo-intima overgrowth.

[Adamantinoma of the tibia and osteofibrodysplasia. Report of a case]. / Adamantinome du tibia et ostéo-fibro-dysplasie. A propos d'une observation.

An adamantinoma of the tibia associated with morphologic aspects of osteofibrodysplasia is studied. The ipsilateral fibula has radiological lesions. The first diagnosis was osteofibrodysplasia and the adamantinoma was recognised eighteen years later. Twenty six cases of adamantinoma associated with osteofibrodysplasia have been published in the literature until 1991. The relationship between these two entities is emphasized. This kind of adamantinoma would have a better behaviour than the others.