Intrahepatic venous collaterals in dogs with congenital intrahepatic portosystemic shunts are associated with focal shunt or hepatic vein narrowing

Abstract

Dogs with congenital intrahepatic portosystemic shunts (IHPSS) occasionally have multiple smaller intrahepatic, tortuous blood vessels surrounding the primary shunt. This study was a retrospective, observational design that was also descriptive and anatomic in nature. Objectives were to characterize vascular morphology in IHPSS dogs presenting with intrahepatic venous collaterals (IVCs) relative to IHPSS dogs without IVCs, and to propose reasons for IVC development. The authors hypothesized that (a) IVCs develop secondary to flow resistance around a focal area of a shunt or draining hepatic vein narrowing and (b) the presence of IVC is associated with portal vessel development before intervention. Anonymized CT angiograms (CTA) and fluoroscopic portovenograms (FPV) of dogs with IHPSS were evaluated for the presence of IVCs, focal narrowing within the IHPSS, and intrahepatic portal vessels >5 mm long. Eleven of 47 (23%) dogs had IVCs identified. IVCs were significantly associated with focal narrowing in the shunt or draining hepatic vein on CTA (P = 0.039) and FPV (P = 0.021). IVCs were not associated with the presence of intrahepatic portal branches >5 mm long on portovenography (P = 0.42) or CTA (P = 0.49). Focal narrowing in the shunt (circumferential soft tissue narrowing >20% of the shunt diameter) was significantly associated with intrahepatic portal branches >5 mm long on both modalities (P < 0.001). IVCs are associated with focal narrowing of the shunt or draining hepatic vein in dogs with IHPSS. IVC should be distinguished from other conditions when evaluating a CTA for canine IHPSS.

Congenital Portosystemic Shunts in Dogs and Cats: Classification, Pathophysiology, Clinical Presentation and Diagnosis

“…They may open into the caudal vena cava or any hepatic vein branch. The morphology of ICPSS has been described in detail using CTA in recent studies [ 17 , 18 , 19 , 20 , 21 , 22 ]. In addition, new classification schemes of ICPSS based on their morphology have been proposed [ Table 1 ] [ 18 , 19 ].…”

Canine intrahepatic portosystemic shunts: Interlobar and intralobar classifications

“…Finally, it is unknown how this assessment applies when there is more than one IPSS, including collaterals. 1 In conclusion, using portal CTA, we showed that canine congenital intrahepatic shunts pass between liver lobes in an identifiable fissure (interlobar) or through a specific lobe (intralobar). Interlobar…”

“…Although convenient, these classifications might not be reliable descriptors because the divisions have been variably defined in the literature, either by the lobe through which the shunt passes or by the direction the shunt enters the CVC. 1,2,5,22 The two longitudinal fissures that pass through the liver conveniently divide the liver into three groups of lobes. Additionally, the right divisional lobes tend to drain into the right side of the CVC; central divisional lobes, ventral side of the CVC; left divisional lobes, left side of the CVC.…”

“…Traditionally, an IPSS has been classified as left, central, or right divisional. Although convenient, these classifications might not be reliable descriptors because the divisions have been variably defined in the literature, either by the lobe through which the shunt passes or by the direction the shunt enters the CVC 1,2,5,22 . The two longitudinal fissures that pass through the liver conveniently divide the liver into three groups of lobes.…”

“…A portosystemic shunt is a vascular formation that circumvents the liver's capillary bed and connects two venous systems. These abnormalities are due to persistent blood flow through a normal embryonic shunt (ductus venosus), development of an anomalous embryonic shunt, or recruitment of blood flow through collateral blood vessels 1 . Portosystemic shunts are broadly classified as intrahepatic or extrahepatic, and this study focused on canine intrahepatic portosystemic shunts.…”