Characteristics of the location and the degree of PV thrombosis PV thrombosis n = 15% Thrombosis location Branches of PV 4 26.7 Main PV 4 26.7 Spread 7 46.6 Thrombosis degree Grade I 2 13.3 Grade II 6 40.0 Grade III 2 13.3 9 Grade IV 5 33.4 Total 15 100 Comment: In 15 patients with PV thrombosis, 4/15 cases (26.7%) had thrombosis in the branches, 4/15 cases (26.7%) in the main PV, and 7/15 cases (46.6%) in both branches and main PV.