Splenic hypertension.....

CT Angiography Identifies Collaterals in Dogs with Splenic Vein Obstruction and Presumed Regional Splenic Vein Hypertension

Swan Specchi, Giovanna Bertolini

Background
Occlusion of the splenic vein (SV), without concurrent portal vein obstruction, can lead to localized splenic hypertension, also known as regional or left-sided portal hypertension. In humans, this condition is associated with pancreatitis and pancreatic tumors and can cause gastrointestinal hemorrhage due to the formation of collateral circulation. In dogs, the presence of splenic venous collaterals has been described in cases of portal hypertension, but little is known about their occurrence in isolated SV obstruction. This study aimed to assess collateral circulation in dogs with isolated SV occlusion and presumed regional splenic vein hypertension using computed tomography (CT) angiography.

Methods
This retrospective study included dogs that underwent CT scans between 2014 and 2019. Cases were identified using medical records and imaging reports, selecting dogs with confirmed SV obstruction but without portal vein thrombosis or evidence of generalized portal hypertension. CT scans were analyzed to determine the presence and characteristics of collateral circulation. Liver function tests were reviewed to rule out hepatic insufficiency.

Results
Out of 46 initially identified cases, 21 met the inclusion criteria. The causes of SV obstruction included splenic pedicle torsion (15/21), tumor invasion (4/21), and thrombosis (2/21). None of the included dogs showed signs of liver dysfunction. Collateral circulation was detected in 4 of 21 dogs, with pathways involving the left gastroepiploic vein (4/4), left gastric vein (2/4), and splenogonadal vein (1/4). CT imaging confirmed that these dogs had normal portal vein patency, distinguishing regional splenic hypertension from generalized portal hypertension.

Limitations
The small sample size limited the ability to categorize collateral pathways based on obstruction level and severity. Additionally, distinguishing regional splenic hypertension from portal hypertension can be challenging, as some collateral patterns overlap between the two conditions. Further studies with larger case numbers and hemodynamic assessments are needed.

Conclusions
CT angiography effectively identified collateral circulation in dogs with isolated SV obstruction, supporting the diagnosis of regional splenic hypertension. This study provides important imaging criteria to differentiate regional splenic hypertension from generalized portal hypertension. The findings highlight the utility of CT in evaluating vascular anomalies in dogs and suggest that SV obstruction should be considered in patients with unexplained splenic venous collaterals.

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