New Study Maps Surprising Variations in Feline Portal Veins—Key Insights for CT and Surgery

Anatomical variations in the tributaries of the normal feline extrahepatic portal system: evaluation with CT angiography

Moniek MWM Dekkers, Nausikaa Devriendt, Hilde de Rooster, Jimmy Saunders, Emmelie Stock

Background

The anatomy of the feline extrahepatic portal vein (EHPV) is often assumed to resemble that of the dog, yet prior studies report inconsistent and conflicting descriptions regarding feline portal tributaries. Accurate knowledge of normal portal venous anatomy is essential for diagnosing and managing vascular anomalies, thrombosis, and complex hepatovascular diseases. This study aimed to characterize the normal anatomical variations of major EHPV tributaries in a large cohort of cats using CT angiography (CTA), providing clarity on species-specific patterns.

Methods

This retrospective, descriptive, cross-sectional study reviewed abdominal CTA scans of cats imaged between January 2020 and July 2024 at Ghent University. Inclusion required ventral recumbency, complete abdominal coverage, and adequate portal contrast. Scans were excluded for vascular anomalies, thrombi, artifacts, poor contrast, or obstructive abdominal masses. Three observers (a diagnostic imaging diplomate, a surgical diplomate, and a diagnostic imaging resident) evaluated all scans in consensus. Tributaries assessed included the splenic vein (SV), left gastric vein (LGV), right gastric vein (RGV), cranial pancreaticoduodenal vein (CrPDV), and gastroduodenal vein (GdV). Vein insertion site, order, orientation, EHPV:aorta ratio, and hilus course were recorded.

Results

Fifty-two CTA scans met criteria. The SV was consistently present as the most caudal EHPV tributary. Considerable variability occurred in LGV anatomy: 28 cats had two LGV branches (one entering the SV, one entering the EHPV), 14 had a single LGV inserting directly into the EHPV, eight had an LGV inserting solely into the SV (the pattern typical of dogs), and two lacked an identifiable LGV. The GdV was present in 38 cats; in 14 cats the RGV and CrPDV merged and entered the EHPV without forming a distinct GdV. In cats with an LGV, it was the most cranial tributary in 85.7% of cases. Insertion orientations varied widely, with the SV most often entering left-laterally, the LGV left-ventrally, and the GdV or combined RGV/CrPDV right-ventrolaterally. The mean EHPV diameter was 6.0 mm, with an EHPV:aorta ratio of 1.5. At the liver hilus, the EHPV coursed straight in one-third of cats and showed a 360° anticlockwise curve in two-thirds.

Limitations

Because the study relied on retrospective clinical CTA scans, selection bias is possible, and the study population may not fully represent healthy cats. Breed diversity was limited, reducing assessment of potential breed-specific patterns. CTA resolution and blooming artifacts sometimes hindered differentiation of closely situated veins, particularly RGV and CrPDV. The absence of identifiable LGV in some cats could not be definitively explained. Additional modalities such as corrosion casting or micro-CT could enhance anatomical precision.

Conclusions

Substantial anatomical variation exists in feline EHPV tributaries, particularly involving the LGV and GdV. The feline portal system differs markedly from the canine pattern, emphasizing that canine anatomy cannot be directly extrapolated to cats. Knowledge of this variability is critical for accurate interpretation of CT angiography, surgical planning, and diagnosis of portal vascular disorders.

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