Classification of portosystemic shunts entering the caudal vena cava at the omental foramen in dogs.

R N White,C Shales,C Warren‐Smith,A T Parry

doi:10.1111/jsap.13209

Abstract

To re-evaluate the anatomy and classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen. A retrospective review of a consecutive series of dogs undergoing CT angiography as part of the diagnostic work-up for a congenital extrahepatic portosystemic shunt. In total, 53 dogs met the inclusion criteria revealing four anatomically distinct omental foramen shunt types; one of which (32 of 53 dogs) showed no shunting blood flow through the right gastric vein and three of which (21 of 53 dogs) involved shunting flow through this vessel. The anatomy of these four distinct shunt types, as defined by CT angiography, was found to be highly consistent. In all cases, regardless of the tributary vessels, the left gastric vein was the final vessel that communicated with the caudal vena cava. Using these findings, a more accurate naming classification for congenital portosystemic shunts entering the caudal vena cava at the level of the omental foramen was proposed. A precise pre-treatment anatomical classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen is important for a more complete understanding of the severity of clinical signs and prognosis, and for the better communication between clinicians and researchers in this clinical field.

Highlights

By using techniques such as computed tomography angiography (CTA), intra-operative mesenteric portovenography (IOMP) and gross visual findings, the anatomy of congenital extrahepatic portosystemic shunts (EHPSSs) have been described previously (Nelson &Nelson 2011, Kraun et al 2014, Fukushima et al 2014, Or et al 2016, White & Parry 2013, 2015, 2016a,b)
When comparing the use of CTA and IOMP to image the portal vasculature in both normal dogs and in dogs suffering from congenital EHPSSs, it has been shown that there is a large difference between the ability of the two techniques to delineate the portal vasculature (Parry & White 2015, 2017)
The median age of dogs presenting with an EHPSS entering the caudal vena cava at the level of the epiploic foramen was 14 months

Summary

Introduction

By using techniques such as computed tomography angiography (CTA), intra-operative mesenteric portovenography (IOMP) and gross visual findings, the anatomy of congenital extrahepatic portosystemic shunts (EHPSSs) have been described previously (Nelson &Nelson 2011, Kraun et al 2014, Fukushima et al 2014, Or et al 2016, White & Parry 2013, 2015, 2016a,b). In a further recent study in which a comprehensive literature review of congenital EHPSS anatomy was performed, it was concluded that in dogs four consistent shunt types (spleno-caval, left gastro-phrenic, left gastro-azygos and those involving the right gastric vein (the so-called “right gastro-caval”), were responsible for 94% of extrahepatic shunts reported in the species (White et al 2018) These four most common EHPSSs have been shown to communicate at consistent sites with a number of systemic veins including the caudal vena cava (CVC) and the azygos and left phrenic veins (Nelson & Nelson 2011, Kraun et al 2014, Fukushima et al 2014, Or et al 2016, White & Parry 2013, 2015, 2016a, White et al 2018). CTA consistently visualised the extrahepatic portal vasculature more completely than IOMP and, as such, might be considered the modality of choice for imaging the portal vasculature in clinical cases (Bertolini et al 2006, Parry & White 2015, 2017, Bertolini 2019)

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