Effects of partial splenic embolization and portosystemic shunt occlusion on portal venous hemodynamics using 4D flow...

To quantitatively evaluate changes in portal venous hemodynamics after partial splenic embolization (PSE) and portosystemic shunt occlusion (PSO) using four-dimensional (4D) flow magnetic resonance imaging (MRI).

This retrospective cohort study included 30 procedures (16 PSE and 14 PSO) performed between 2019 and 2025. Flow rates were measured in the main portal vein (MPV), splenic vein (SpV), superior mesenteric vein (SMV), and portosystemic shunts (PSS) using pre- and post-procedural 4D flow MRI. For PSE, correlations were assessed between changes in MPV and SpV flow, and between vessel-specific flow change ratios and the embolic volume ratio. For PSO, changes in MPV flow were compared based on whether all PSS were treated, and correlation was assessed between flow changes in MPV and PSS flow.

After PSE, MPV flow decreased (median, 751.0 to 441.5 mL/min; p = 0.025) as did SpV flow (482.5 to 323.0 mL/min; p = 0.001), whereas SMV flow remained unchanged. Changes in MPV and SpV flow were strongly correlated (ρ = 0.726, p = 0.002). The embolic volume ratio showed a moderate correlation with the SpV flow change ratio (ρ = 0.563, p = 0.036), but not with the MPV flow change ratio. After PSO, MPV flow increased (544.5 to 692.5 mL/min; p < 0.001), along with SpV flow (63.0 to 231.5 mL/min; p = 0.001), while SMV flow did not change significantly. The increase in MPV flow was greater when all PSS were treated than when they were not (140.0 vs. 17.0 mL/min; p = 0.019), and was not correlated with PSS flow.

4D flow MRI demonstrates that PSE decreases portal and splenic venous flow, whereas PSO increases both. These findings provide quantitative insight into complex treatment-related hemodynamic changes in the portal venous system.