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A PSS classification system
VRU 2024
Chick Weisse, William Alexander Fox-Alvarez, Federico R Vilaplana Grosso, et al.
Background
Congenital extrahepatic portosystemic shunts (EHPSS) are vascular anomalies in dogs characterized by abnormal connections between the portal and systemic circulatory systems. This study aimed to create an anatomical-based classification system for EHPSS using CT angiography, identifying the prevalence and morphological variations of these shunts in a large canine population. The study also sought to explore associations with patient demographics and portal perfusion.
Methods
This retrospective, multi-institutional study analyzed 1,082 canine CT angiograms collected from 13 institutions. Inclusion criteria included dogs under 12 kg with diagnostic-quality CT scans showing up to three congenital EHPSS and no history of shunt surgery. The shunts were classified based on portal and systemic vessels involved, with contributing portal vessels identified. Hepatic portal perfusion was subjectively graded on a five-point scale. Statistical analyses examined associations between shunt morphology and demographic or clinical variables.
Results
-Forty-five unique shunt conformations were identified, with five types accounting for 85% of cases. The most common shunts involved the left gastric vein and included:
-Left gastric-phrenic (27%),
-Left gastric-azygos (19%),
-Left gastric-caval (15%),
-Aberrant left gastric-caval with right gastric vein contribution (12%),
-Aberrant left gastric-caval with right gastric and short gastric vein contributions (11%).
-The left gastric vein was the portal vessel of origin in 95% of cases, while systemic vessels of insertion included the caudal vena cava (47%), phrenic vein (31%), and azygos vein (21%).
-Portal perfusion scores (PPS) varied significantly with shunt type, age, breed, and vessel characteristics. Dogs with certain shunt morphologies (e.g., left gastric-phrenic) had better PPS, while others (e.g., left gastric-caval) had poorer scores.
Limitations
Retrospective data and non-standardized imaging protocols may limit the generalizability of findings. Subjective portal perfusion grading lacked objective validation, and potential underdiagnosis of certain shunt morphologies could have occurred.
Conclusions
The proposed anatomical classification system provides a standardized framework for identifying and comparing EHPSS in dogs. The findings highlight the predominance of left gastric vein shunts and the clinical significance of portal perfusion scores in understanding outcomes. This system may improve diagnostic accuracy, treatment planning, and prognostication for affected dogs.
Normal canine portal venous anatomy (NORMAL) and the five most common shunt subtypes, including left gastric-phrenic (LGP), left gastric-azygos (LGA), left gastric-caval (LGC), aberrant left gastric-caval with right gastric vein contribution (aLGC + RGV), and aberrant left gastric-caval with right gastric vein and short gastric vein contributions (aLGC + RGV + SGV). The recommended location for shunt attenuation is marked in green. Labeled portal vessels include portal vein (PV), gastrosplenic vein (GSV), left gastric vein (LGV), splenic vein (SV), short gastric vein (SG), gastroduodenal vein (GDV), right gastric vein (RGV), gastroepiploic vein (GEV), right portal vein (RPV), and left portal vein (LPV). Labeled systemic veins include caudal vena cava (CDVC), phrenic vein (Phrenic), and azygos vein (Azyg).
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