Sara Vieri 1, Mirko Mattolini 1, Beatrice Gianni 1, Elvanessa Caleri 1, Federica Rossi 1
Background
Segmental caudal vena cava (CdVC) aplasia, also known as azygos continuation of the CdVC, is a rare congenital vascular anomaly. It results from failed embryological development connecting prehepatic and hepatic CdVC segments, leading to redirection of postrenal blood to the azygos vein. This report presents the first comprehensive imaging description (ultrasound, radiographs, and CT) of segmental CdVC aplasia in a cat, incidentally discovered during evaluation for unrelated gastrointestinal symptoms.
Methods
A 10-year-old neutered male domestic shorthair cat with acute lethargy, dysorexia, and vomiting underwent abdominal ultrasound (AUS), thoracic radiographs, and triple-phase CT angiography. Imaging evaluated CdVC morphology, vessel continuity, and any accompanying vascular or anatomical anomalies. Data were interpreted using standard DICOM viewers and reviewed for abnormal vessel paths and signs of blood flow disturbance.
Results
AUS showed a dorsally displaced, tortuous CdVC with spontaneous echo contrast and no visual continuity cranially. Thoracic radiographs revealed an abnormally enlarged azygos vein. CT confirmed prehepatic CdVC aplasia, with postrenal blood redirected to the azygos vein, which drained into the cranial vena cava. The hepatic veins and portal system were normal. No thrombi or other vascular anomalies were identified. A protrusion of retroperitoneal fat through the aortic hiatus was also noted. Gastrointestinal symptoms resolved with supportive care, and no long-term issues were observed.
Limitations
This is a single case, limiting generalizability. The vascular anomaly was incidentally found in an adult cat without prior imaging, and its clinical relevance remains uncertain. Potential complications such as thromboembolism were not seen but may occur in similar cases.
Conclusions
Segmental CdVC aplasia can be incidentally detected in cats using multimodal imaging. Recognizing this anomaly is crucial to avoid misdiagnosis, especially when vascular structures deviate from expected anatomy. CT angiography is essential for definitive diagnosis and surgical planning when vascular anomalies are suspected.
Sagittal (A) and dorsal (B) CT reformatted images from the venous postcontrast series showing the abnormal vessel (white arrows) located cranially to the junction of the renal veins (asterisks). The vein courses dorsomedially to the right kidney (RK), runs parallel to the aorta (thin white arrows), and drains into the azygos vein (Az). The posthepatic and hepatic portions of the caudal vena cava are visible (arrowheads). The caudal portion of the portal vein (PV) is within normal limits. No anomalies in the portal system were found. The transverse CT image (lung window settings—C) shows the aortic hiatus through which retroperitoneal fat tissue herniates into the thoracic cavity (black arrows). CrVC, cranial vena cava; PV, portal vein; Sp, spleen; St, stomach.
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