ULTRASONOGRAPHIC DIAGNOSIS OF PORTOSYSTEMIC SHUNTING IN DOGS AND CATS

Marc-André D'Anjou, Dominique Penninck, Lilian Cornejo, Philippe Pibarot

Background
Portosystemic shunts (PSSs) are vascular anomalies that redirect portal blood away from the liver, causing systemic toxin circulation and associated clinical signs. This study evaluates the diagnostic accuracy of ultrasonography for detecting and characterizing PSSs in dogs and cats, with a focus on identifying morphological features, portal venous ratios, and secondary findings like hepatic microvascular dysplasia (HMD).

Methods
The study included 85 dogs and 17 cats with suspected PSSs, confirmed via portography, scintigraphy, or necropsy. Ultrasonographic assessments were made retrospectively (1998–2001) and prospectively (2001–2002) using Doppler and grayscale imaging. Parameters such as liver size, portal vein dimensions, flow velocity, and vessel-to-aorta/vena cava ratios were measured and correlated with diagnostic accuracy.

Results
Ultrasonography achieved 92% sensitivity, 98% specificity, and 95% accuracy for detecting PSSs. Extrahepatic PSSs were identified in 42 cases (33 dogs, 9 cats), intrahepatic PSSs in 11 dogs, and multiple acquired PSSs in 6 dogs. Key findings included:

-Reduced portal vein/aorta (PV/Ao ≤0.65) and portal vein/caudal vena cava ratios (PV/CVC ≤0.8) in animals with extrahepatic PSSs.
-Secondary signs, such as microhepatica (84% in dogs with congenital PSSs), renomegaly (59%), and urolithiasis (70%), provided supportive evidence.
-Turbulent blood flow in the caudal vena cava predicted PSS termination in that vein with 91% positive predictive value.

Limitations
The study's reliance on retrospective data and variation in ultrasonographic protocols could introduce bias. Additionally, the sample size for cats and certain PSS types was small, limiting the generalizability of findings. Some secondary diagnostic criteria, like portal vessel visibility, lacked objective quantification.

Conclusions
Ultrasonography is highly effective for diagnosing PSSs in dogs and cats, particularly when combined with Doppler assessments of flow turbulence and portal venous ratios. This modality provides critical morphological details that guide surgical planning. However, subtle shunts may require additional imaging or repeat ultrasonography.

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