Passive Stent Expansion as a Confounder in Under‐Dilated TIPS Outcomes

We read with great interest the recent article by Roccarina et al. [1] which evaluates the impact of endoprosthesis under-dilation on the prevention of portal hypertension–related complications beyond primary TIPS indication. The authors conclude that under-dilated TIPS (U-TIPS) provides protection comparable to standard dilation, independent of achieving conventional hemodynamic targets. While this is an important and clinically relevant question, we believe that a key technical factor, namely passive expansion of the stent grafts used in the study, may significantly influence the interpretation of these findings. The study cohort predominantly utilised first-generation ePTFE-covered stent grafts (VIATORR), particularly during the earlier study period. These devices are composed of self-expanding nitinol, which exerts a continuous outward radial force. It is well established that such stents, even when initially under-dilated (e.g., 6–8 mm), tend to passively expand over time toward their nominal diameter [2, 3]. This phenomenon is intrinsic to nitinol and has been consistently demonstrated in both imaging-based and clinical follow-up studies. The implications of passive expansion are directly relevant to the authors' conclusions. If under-dilated stents progressively enlarge, the distinction between U-TIPS and standard TIPS (S-TIPS) may not be maintained during follow-up. As a result, a proportion of patients categorised as U-TIPS may ultimately function as larger shunts, thereby attenuating differences in portal decompression and clinical outcomes between groups. The reported equivalence between U-TIPS and S-TIPS may therefore reflect delayed convergence of effective shunt diameters rather than true independence from hemodynamic targets. This concern is supported by prior studies demonstrating that 10-mm nominal stents under-dilated to 8 mm frequently approach near-nominal diameters on follow-up, leading to progressive reductions in portal pressure gradient and increased shunt flow, with potential implications for both efficacy and complications such as hepatic encephalopathy [3]. The development of controlled-expansion stents (VIATORR-CX), designed to maintain a fixed diameter unless actively re-dilated, further underscores the clinical relevance of this issue [4]. Another limitation is the lack of serial post-TIPS portocaval pressure gradient measurements during follow-up. As the gradient is known to increase in the early post-procedural period, reliance on intraoperative values alone may result in misclassification of hemodynamic response, further complicating interpretation of the findings [5]. In summary, passive stent expansion and the absence of longitudinal hemodynamic assessment represent important unaddressed variables that may confound the study's conclusions. Accounting for these factors is essential before inferring that under-dilation is independent of clinical outcomes. The authors declare no conflicts of interest. This article is linked with http://doi.org/10.1111/liv.70606. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.