Portal Vein/Aorta Ratio in Dogs with Acquired Portosystemic Collaterals

Background: The portal vein (PV) diameter increases in humans with portal hypertension (PH). However, there is no evidence of PV enlargement in dogs with PH. Objectives: To measure the PV-to-aorta (PV/Ao) ratio in dogs with PH (chronic hepatitis [CH], primary hypoplasia of the PV [PHPV]), in dogs with extrahepatic congenital portosystemic shunt (EH-CPSS), and in healthy dogs, and to evaluate the relationship between PV/Ao ratio and splenic pulp pressure (SPP). Animals: Twenty-five dogs with acquired portosystemic collaterals (APSCs; 15 with CH, 10 with PHPV), 32 dogs with EH-CPSS, and 20 healthy dogs. Methods: Retrospective study. The PV/Ao ratio was calculated with images obtained by computed tomography. SPP was measured at the time of liver biopsy in 45 dogs. Results: Median PV/Ao ratio was similar between dogs with CH (1.35, range 1.05–2.01) and healthy dogs (0.95, 0.80–1.15), but differed significantly between the CH group and both the PHPV (0.40, 0.24–0.67) and EH-CPSS groups (0.30, 0.11–0.64) (P <.001). The PV/Ao ratio was significantly lower in the PHPV group than in healthy dogs (P <.05). It also correlated positively with SPP (r_s = 0.71; P <.001). However, there was no intragroup correlation between SPP and the PV/Ao ratio in any group. Conclusions and Clinical Importance: The PV/Ao ratio can be evaluated in dogs with APSCs on computed tomography. Further studies are needed to examine the relationship between SPP and the PV/Ao ratio in larger groups of dogs with PH and to determine its clinical relevance.