Evaluation of the presence and severity of spontaneous splenorenal or gastrorenal shunts via four-dimensional flow magnetic resonance imaging: a preliminary study

Background: Four-dimensional phase-contrast magnetic resonance imaging (4D flow MRI) is a relatively new type of MRI acquisition technique that provides a unique and comprehensive set of information within a single acquisition, including hemodynamic and anatomical information. This study was designed to noninvasively evaluate the correlation between the presence and severity of spontaneous splenorenal shunt (SRS) or gastrorenal shunt (GRS) and 4D flow MRI-derived parameters.

Methods: This retrospective case-control study enrolled 70 patients who were diagnosed with hepatocirrhosis portal hypertension and admitted to the Second Affiliated Hospital of Chongqing Medical University. Patients were divided into three groups according to the diameter of the SRS and GRS. 4D flow MRI-derived parameters, including the turbulent kinetic energy, total volume (TV), flow velocity, blood flow volume (BFV), maximum flow (MF), wall shear stress, and relative pressure, were obtained for eight cut planes: proximal to the splenomesenteric confluence and liver hilum of the portal vein (PV₁/PV₂); the left/right branch of the bifurcation of the PV (LPV/RPV), at the mesosplenic confluence of the splenic vein (SV₁), at the splenic hilum of the SV (SV₂); at the proximal to the splenomesenteric confluence of the superior mesenteric vein (SMV₁), and 5 cm from the splenomesenteric confluence of the SMV (SMV₂). Comparisons among the three groups were based on one-way analysis of variance (ANOVA). Logistic regression was used to identify the risk factors for small SRS/GRS (S-SRS/GRS) and for large SRS/GRS (L-SRS/GRS). Receiver operating characteristic curves were used to evaluate the diagnostic performance of the independent risk factors for SRS and GRS. The associations between the clinical data and the 4D flow MRI-derived parameters of GRS and SRS were assessed via Spearman correlation coefficient analysis.

Results: The presence of SRS or GRS was correlated with TV_LPV (r=-0.302; P=0.035), TV_PV1 (r=-0.385; P=0.001), TV_PV2 (r=-0.301; P=0.013), BFV_PV1 (r=-0.360; P=0.010), BFV_SMV2 (r=0.371; P=0.008), MF_PV1 (r=-0.341; P=0.004), and MF_PV2 (r=-0.291; P=0.017). Meanwhile, the severity of the SRS or GRS was correlated with alanine aminotransferase level (r=-0.535; P<0.001), BFV_LPV (r=-0.560; P=0.008), aspartate aminotransferase level (r=-0.321; P=0.038), and model for end-stage liver disease score (r=0.323; P=0.039). TV_PV1, TV_PV2, BFV_PV1, BFV_PV2, and MF_SMV2 were found to be independent risk factors for L-SRS/GRS, with intermediate diagnostic efficacy, with the area under the curve (AUC)_{TV PV1}=0.706 [95% confidence interval (CI): 0.519-0.853; sensitivity, 61.54%; specificity, 80.77%; P=0.018], AUC_{BFV PV1} =0.694 (95% CI: 0.507-0.844; sensitivity, 95.00%; specificity, 63.16%; P=0.035), AUC_{TV PV2} =0.729 (95% CI: 0.544-0.870; sensitivity, 77.78%; specificity, 66.67%; P=0.016), AUC_{BFV PV2} =0.718 (95% CI: 0.531-0.862; sensitivity, 60.00%; specificity, 82.35%; P=0.017), and AUC_{MF SMV2} =0.788 (95% CI: 0.608-0.912; sensitivity, 44.00%; specificity, 84.46%; P=0.005), respectively. As the TV of PV1 and PV2 and the BFV of PV1 and PV2 decreased, the risk of L-SRS/GRS increased. As the MF of SMV2 increased, the risk of the presence of L-SRS/GRS increased.

Conclusions: 4D flow MRI-derived parameters correlated with the presence and severity of SRS or GRS. Meanwhile, the independent risk factors for the presence of L-SRS/GRS were the TV of LPV, PV1, and PV2; the BFV of PV1 and SMV2; and the MF of PV1 and PV2.