Influences of Anatomorphological Features of the Portal Venous System on Postsplenectomy Hemodynamic Characteristics in Patients With Portal Hypertension: A Computational Model-Based Study

Abstract

Splenectomy, as an effective surgery for relieving complications caused by portal hypertension, is often accompanied by a significantly increased incidence of postoperative thrombosis in the portal venous system (PVS). While the underlying mechanisms remain insufficiently understood, the marked changes in hemodynamic conditions in the PVS following splenectomy have been suggested to be a potential contributing factor. The aim of this study was to investigate the influences of the anatomorphological features of the PVS on hemodynamic characteristics before and after splenectomy, with emphasis on identifying the specific anatomorphological features that make postoperative hemodynamic conditions more clot-promoting. For this purpose, idealized computational hemodynamics models of the PVS were constructed based on general anatomical structures and population-averaged geometrical parameters of the PVS. In the models, we incorporated various anatomorphological variations to represent inter-patient variability. The analyses of hemodynamic data were focused on the spatial distribution of wall shear stress (WSS) and the area ratio of wall regions exposed to low WSS (ALS). Obtained results showed that preoperative hemodynamic conditions were comparable among different models in terms of space-averaged WSS and ALS (all were small) irrespective of the considerable differences in spatial distribution of WSS, whereas, the inter-model differences in ALS were significantly augmented after splenectomy, with the value of ALS reaching up to over 30% in some models, while being smaller than 15% in some other models. Postoperative ALS was mainly determined by the anatomical structure of the PVS, followed by some morphogeometrical parameters, such as the diameter and curvature of the splenic vein, and the distance between the inferior mesenteric vein and splenoportal junction. Relatively, the angles between tributary veins and trunk veins only had mild influences on ALS. In addition, a marked increase in blood viscosity was predicted after splenectomy, especially in regions with low WSS, which may play an additive role to low WSS in initiating thrombosis. These findings suggest that the anatomical structure and some morphogeometrical features of the PVS are important determinants of hemodynamic conditions following splenectomy, which may provide useful clues to assessing the risk of postsplenectomy thrombosis based on medical imaging data.

The effect of splenic vein diameter on the diagnosis of portal vein thrombosis

“…where $$\vec{u}$$ and p represented the fluid velocity vector and pressure, respectively; ρ represents a fluid density of 1060 kg/m 3 and μ represents a fluid viscosity of 0.0045 Pa s 18,20 …”

“…Therefore, the following models with different geometric morphological parameters were established in this study, and only morphological parameters changed on the basis of type 1 anatomical structure were shown: (1) Only the distance between IMV and PV (Figure 1b); (2) Only the angles of IMV and SV are changed (Figure 1c); (3) Only the angles of PV and SV are changed (Figure 1d); (4) Only the curvature of SV is changed (Figure 1e). 18 And on these basic models, the D SV increases by 1 mm, from 8 to 12 mm.…”

“…16,17 Furthermore, there were large individual differences in the distance between the IMV and the PV (Figure 1b1-b3), the angle of the IMV and the SV (Figure 1c1-c3), the angle of the SV and PV (Figure 1d1-d3), and the curvature of the SV (Figure 1e1-e2). 18 However, to date, how the PV geometry affects changes in the hemodynamic environment of the PV and thus the risk of PVT has not been studied in the clinic (Figure 2).…”

A computational model-based study on the feasibility of predicting post-splenectomy thrombosis using hemodynamic metrics

“…Some previous studies employed computational models to address various issues related to the portal venous system such as the diagnosis of portal hypertension ( Wang et al, 2017 ; Wang et al, 2018 ; Wang et al, 2020 ) and the hemodynamic changes due to cirrhosis ( George et al, 2015 ; Wei et al, 2017 ). In our previous study, the influence of anatomorphological features of the portal venous system on post-splenectomy hemodynamic characteristics was investigated based on idealized computational models ( Wang et al, 2021 ). Moreover, we also conducted a proof-of-concept study that preliminarily indicated the association between hemodynamic metrics and post-splenectomy thrombosis based on three patient-specific models ( Wang et al, 2022 ).…”

A novel potential mechanism for the development of portal vein thrombosis in cirrhosis based on portal hemodynamics

“…The marked changes in hemodynamics in cirrhosis have been suggested to be a potential contributing factor to the formation of PVT. When the portal vein (PV) velocity decreases to 15 cm/s, patients with cirrhosis have a highly significant risk association with the future development of PVT [ 11 ], and the changes in hemodynamic characteristics after splenectomy increase the risk of PVT development [ 12 , 13 ]. While the anatomical structure of the portal venous system plays a significant role in the development of its flow features and hemodynamic parameters.…”