Table 1.

Yerdel Classification (2000)

Grade	Characteristic
Grade 1	Minimally or partially thrombosed PV where thrombus is mild or confined to < 50% of the lumen with or without extension into the SMV.
Grade 2	> 50% occlusion including total occlusion with or without minimal extension into the SMV.
Grade 3	Complete thrombosis of both the PV and proximal SMV.
Grade 4	Complete thrombosis of the PV and both proximal and distal SMV.

Abbreviations: PV: portal vein; SMV: superior mesenteric vein