Portal vein branching anatomy demonstrates predictable patterns with several common variants that are highly relevant in hepatobiliary surgery, transplantation, portal vein embolization (PVE), and interventional radiology. > [!tip] Branching Pattern Mnemonic > The three most clinically important portal vein branching configurations can be conceptualized like letters: > > - **Type I → “Y”** > - **Type II → “X”** > - **Type III → “H”** ![[Pasted image 20260514205517.png]] --- ### Type I — Standard Bifurcation (“Y”) - **Frequency:** ~65–80% - Classic portal venous anatomy consists of bifurcation of the main portal vein into: - Right portal vein (RPV) - Left portal vein (LPV) - The right portal vein subsequently divides into: - Right anterior portal vein (RAPV) - Right posterior portal vein (RPPV) --- ### Type II — Trifurcation (“X”) - **Frequency:** ~10–15% - In trifurcation anatomy, the main portal vein simultaneously gives rise to: - LPV - RAPV - RPPV - There is no true right portal vein trunk. --- ### Type III — Early Posterior / Segmental Branching (“H”) - **Frequency:** ~5–13% - Type III anatomy involves early branching from the main portal vein before formation of a standard right portal vein trunk. - The classic form consists of: - Early origin of the RPPV directly from the main portal vein --- ### Type IV — Separate Segment VII Branch - Segment VII portal branch arises independently from the right PV or directly from the main PV - Can be conceptualized as a subvariant of Type III anatomy with early segmental branching --- ### Type V — Separate Segment VI Branch - Segment VI portal branch arises independently from the right PV - Can similarly be thought of as a Type III-type early segmental branching pattern --- ### Other Rare Variants **Frequency:** ~5% Additional uncommon configurations include: - Accessory portal branches - Duplicated branches - Absent segmental trunks - Complex mixed branching patterns These are less common but may substantially impact operative planning and interventional procedures. --- ### Arterial and bilious overlay ![[Pasted image 20260514210215.png]] ![[Pasted image 20260514210248.png]] ___ ### Conceptualization as a 3D process ![[Pasted image 20260514210430.png|300]] --- ### References > [!cite]- Selected References > > Borhani AA, Elsayes KM, Catania R, Kambadakone A, Furlan A, Kierans AS, et al. *Imaging Evaluation of Living Liver Donor Candidates: Techniques, Protocols, and Anatomy.* RadioGraphics. 2021;41(6). [Site Link](https://pubs.rsna.org/doi/10.1148/rg.2021210012) > > Cheng YF, Huang TL, Chen CL, et al. *Variation of the intrahepatic portal vein: angiographic demonstration and application in living-related hepatic transplantation.* Transplant Proc. 1996;28(3):1669–1670. [PubMed Link](https://pubmed.ncbi.nlm.nih.gov/15385304/) > > Chernyak V, Fowler KJ, Sirlin CB, et al. *LI-RADS CT/MRI Manual, Chapter 3: Liver Anatomy.* American College of Radiology; accessed 2026. [ACR LI-RADS Liver Anatomy Chapter](https://edge.sitecorecloud.io/americancoldf5f-acrorgf92a-productioncb02-3650/media/ACR/Files/RADS/LI-RADS/Chapter-3--Liver-anatomy.pdf) > > Watanabe N, Ebata T, Yokoyama Y, Igami T, Sugawara G, Mizuno T, Yamaguchi J, Nagino M. *Anatomic features of independent right posterior portal vein variants: Implications for left hepatic trisectionectomy.* Surgery. 2017;161(2):347-354. doi:10.1016/j.surg.2016.08.024. [PubMed Link](https://pubmed.ncbi.nlm.nih.gov/27692569/)