Infrahepatic caudal/inferior vena cava interruption with azygos/hemiazygos continuation. Vascular anomaly in swine

Abstract

Background: Swine are commonly used as a model to study congenital cardiovascular defects that occur in humans and these models have been both spontaneous and experimentally induced. Ventricular septal defect, patent ductus arteriosus, and atrial septal defect (ASD) are examples of experimentally induced models. Absence of caudal/inferior vena cava (CVC/IVC) with azygos/hemiazygos continuation is an uncommon vascular anomaly.

Case report: The vascular anomaly presented in this case report was an incidental finding on a pig that was evaluated for experimental percutaneous atrial septal defect creation and its closure using a percutaneous femoral vein approach. Absence of CVC/IVC was confirmed by venography and necropsy.

Conclusions: To the best of the investigators knowledge, this is the first report of absence of CVC/IVC with azygos/hemiazygos continuation in the swine.

Keywords: azygos vein; congenital vascular anomaly; experimental animal model; hemiazygos vein; inferior vena cava.

FIGURE 1

Ventrodorsal subtraction venogram of the chest in a swine after simultaneous contrast injection into the right jugular vein and right femoral veins. Injection into the right femoral vein demonstrates the large hemiazygos trunks (HAV) draining into the coronary sinus (CS), which then communicates directly with the right atrium (RA). Injection into the right jugular vein shows normal right cranial/superior vena cava (RCSVC) draining into right atrium.

FIGURE 2

The lateral venogram of the chest in a swine after simultaneous injection of the right femoral vein and right jugular veins. The large hemiazygos vein (HAV) ascends along the vertebral column and joins the coronary sinus (CS), which then communicates the directly with the right atrium.

FIGURE 3

Gross specimen of the mediastinum demonstrates entrance of the hemiazygos vein (HAV) into right atrium (RA). The large hemiazygos vein drains into the right atrium across the aorta (Ao) and esophagus (Es).