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Intrahepatic portosystemic shunts just got a whole lot more complicated.....
VRU 2023
Obi Veterinary Education
April 29, 2025
Nicholas D. Walsh, Ian R. Porter, Allison V. Miller, Anthony J. Fischetti, Soon Hon Cheong, Peter V. Scrivani
Background:
The study sought to improve the classification of canine congenital intrahepatic portosystemic shunts (IPSS) by distinguishing between interlobar and intralobar shunts. This distinction was based on the shunt's anatomical location within liver fissures or lobes, which could refine therapeutic planning and improve the consistency of radiological descriptions.
Methods:
The research comprised two parts:
-A prospective anatomical study reviewing normal canine liver morphology using literature, dissection, and CT angiography (CTA) of specimens to map the ductus venosus and other structures.
-A retrospective multi-institutional case series analyzing CTA findings from 56 dogs diagnosed with a single IPSS between 2008 and 2022. Shunts were classified based on their interlobar or intralobar location, afferent and efferent blood flow, and insertion into the caudal vena cava (CVC).
Results:
-Interlobar Shunts (43%): These shunts passed between liver lobes, typically arising from the left portal branch. Four subtypes were identified: patent ductus venosus (PDV), left interlobar, right interlobar, and ventral interlobar. Most connected to the left side of the CVC near the diaphragm.
-Intralobar Shunts (57%): These shunts traversed specific liver lobes, primarily the caudate process or right lateral lobe, originating from the right portal branch. Most drained into hepatic veins before joining the CVC.
-Anatomical differences between interlobar and intralobar shunts influenced their surgical accessibility and potential for treatment, including laparoscopic ligation and liver lobectomy.
Limitations:
The study was constrained by a relatively small sample size, retrospective design, and potential variability in imaging acquisition. It also excluded cases with multiple shunts or incomplete imaging data. These factors may have limited the generalizability of the findings.
Conclusions:
The distinction between interlobar and intralobar IPSS enhances the precision of shunt classification, which is critical for both diagnostic and therapeutic purposes. The study underscores the importance of detailed anatomical descriptions in guiding surgical or interventional treatments. Future research is needed to validate these classifications across larger populations and explore alternative treatments like liver lobectomy.
Illustration of canine liver anatomy, caudoventral aspect (viewed from the umbilicus). The liver includes right (blue), left (orange), caudate (green), and quadrate (red) lobes. Notice that some structures are in fissures and outside the lobes, including most of the portal vein. The location of the porta hepatis is marked by hepatic artery (1), bile duct (2), and portal vein (3). The portal vein splits into right (4) and left portal branches. The left portal branch is divided into transverse (5a) and umbilical (5b) parts by the round/falciform ligaments and ligamentum venosum. These ligaments connect the umbilicus to the left portal branch, and from the left portal branch, the ligamentum venosum continues dorsally, passing between the left lateral liver lobe and papillary process, and then right cranially to join the caudal vena cava (6) at the confluence of the left, middle, and papillary hepatic veins. In some dogs, the falciform ligament continues cranially to the diaphragm. Source, ©Lauren D. Sawchyn, DVM, CMI. [Colour figure can be viewed at wileyonlinelibrary.com]
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