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.