Migration of self-expandable stents: Report of two cases with a transjugular intrahepatic portosystemic shunt and assessment of stent bending elasticity

This study reports partial stent migration after transjugular intrahepatic portosystemic shunt (TIPS). This was considered to be related to high bending elasticity, which tended to straighten stents positioned in a curved TIPS. To further investigate this potentially severe problem caused by nitinol stents a comparative study on the bending elasticity of various elastic stents was performed in an attempt to define their appropriateness for the TIPS procedure. Two patients received TIPS for refractory ascites and variceal bleeding, respectively. After treatment, symptoms improved but reappeared after a few months indicating the need for radiological shunt revision. Catheterization through the shunt could be performed in one patient only. In the second patient a parallel puncture was done and, after diagnosing stent migration, a parallel shunt was established. The brief experimental study compared five self-expandable stents with respect to their bending elasticity. The experimental measurements demonstrated great differences with respect to bending forces in function of bending angle. The two types of nitinol stents used for the TIPS procedure in the patients reported, showed very high bending forces with eventual break at 30 and 45°, respectively. High bending elasticity of nitinol stents may be responsible for stent migration. These stents can not be recommended for the TIPS procedure.