Portal Vein/Aorta Ratio in Dogs with Acquired Portosystemic Collaterals

Abstract

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.

Keywords: Canine; Multidetector computed tomography; Portal hypertension; Splenic pulp pressure.

Figure 1

Curved planar reformation (CPR) images obtained on multidetector computed tomography (MDCT) from a healthy dog. CPR images of the PV (A) and Ao (B) and graphs of these areas. This tool allows quantitative analysis of vascular anatomy without using contrast medium and provides cross‐sectional areas of true orthogonal sections of the PV and Ao at selected anatomic points in unfolded two‐dimensional views. The mean values for the PV and Ao areas were determined at 3 cranial points (0, 5, 10 mm) at the levels of the GDV and the CA. These points comprised points at 5 mm and 10 mm from the 0 mm point on the cranial side of the GDV to the head side and points at 5 mm and 10 mm from the 0 mm point on the cranial side of the CA to the head side, respectively. Ao, aorta; CA, celiac artery; CMA, celiac mesenteric artery; GDV, gastroduodenal vein; PV, portal vein.

Figure 2

CPR images obtained on MDCT from a healthy dog. Orthogonal cross‐sectional images of the PV (A) and Ao (B) are shown. After confirming the site to be measured, the central line is placed at the center of the orthogonal cross‐sectional image of the site, the outline of the blood vessel is manually corrected and reflected on the image, and the cross‐sectional area of the target vessel is measured. The yellow lines indicate the outline of the blood vessel. Ao, aorta; PV, portal vein.

Figure 3

The ratio of the portal vein (PV) to aorta (Ao) in dogs with CH (n = 15), PHPV (n = 10), or EH‐CPSS (n = 32) and in healthy dogs (n = 20). Symbols: ■ healthy dogs; ▲ EH‐CPSS; ● CH; ○ PHPV. The lines indicate the median values. The PV/Ao ratio did not differ between dogs with CH and healthy dogs, but was significantly reduced in dogs with PHPV when compared with healthy dogs and dogs with CH as well as in those with EH‐CPSS when compared with healthy dogs and dogs with CH. *P < .05, ***P < .001. CH, chronic hepatitis; EH‐CPSS, extrahepatic congenital portosystemic shunt; PHPV, primary hypoplasia of the portal vein.

Figure 4

PV/Ao ratio versus SPP in dogs with CH (n = 15), PHPV (n = 8), or EH‐CPSS (n = 16) and in healthy dogs (n = 6). The PV/Ao ratio is significantly and positively correlated with SPP in dogs with CH, those with PHPV, and those with EH‐CPSS, and in healthy dogs. However, there was no intragroup correlation between SPP and the PV/Ao ratio in the dogs with CH, PHPV, or EH‐CPSS, or in the group of healthy dogs. Symbols: ■ healthy dogs; ▲ EH‐CPSS; ● CH; ○ PHPV. CH, chronic hepatitis; EH‐CPSS, extrahepatic congenital portosystemic shunt; PV/Ao, portal vein/aorta; PHPV, primary hypoplasia of the portal vein; SPP, splenic pulp pressure.