Table 1.

Types in BLB classification system based on portal veins of 178 patients

Classification	Description
Type I	Classical anatomy
Type II	Absent RPV
IIa	MPV trifurcation
IIb	RPPV as the first branch of MPV
IIc	RAPV arising from LPV
IId	Absent RPV
Type III	Absent LPV (horizontal portion)
Type IV	Absent RAPV/RAPV
IVa	Separate origin of P8
IVb	Separate origin of P5
IVc	Separate origin of both P8 and P5
IVd	Separate origin of P7
IVe	Separate origin of P6
IVf	Separate origin of both P7 and P6
IVg	RPV quadrifurcation

MPV, main portal vein; LPV, left portal vein; RPV, right portal vein; RAPV, right anterior portal vein; RPPV, right posterior portal vein; P8, segmental VIII branch; P5, segmental V branch; P7, segmental VII branch; P6, segmental VI branch