Azygous continuation of the inferior vena cava

• Azygos continuation of the IVC is AKA absence of the hepatic segment of the IVC with azygos continuation.
• The renal portion of the IVC receives blood return from both kidneys and passes posterior to the diaphragmatic crura to enter the thorax as the azygos vein.
• The azygos vein joins the superior vena cava at the normal location in the right paratracheal space.
• The hepatic segment (often termed the posthepatic segment) is ordinarily not truly absent; rather, it drains directly into the right atrium.
• Each gonadal vein drains to the ipsilateral renal vein.

• Formerly thought to be predominantly associated with severe congenital heart disease and asplenia or polysplenia syndromes, azygos continuation of the IVC has become increasingly recognized in otherwise asymptomatic patients since the advent of cross-sectional imaging.
• It is important to recognize the enlarged azygos vein at the confluence with the superior vena cava and in the retrocrural space to avoid misdiagnosis as a right-sided paratracheal mass or retrocrural adenopathy.
• Preoperative knowledge of the anatomy may be important in planning cardiopulmonary bypass and to avoid difficulties in catheterizing the heart.

• The renal portion of the IVC receives blood return from both kidneys and passes posterior to the diaphragmatic crura to enter the thorax as the azygos vein.
• The azygos vein joins the superior vena cava at the normal location in the right paratracheal space.

Image shown below is courtesy of RadsWiki and copylefted

Images shown below are courtesy of RadsWiki and copylefted

• Double inferior vena cava
• Left inferior vena cava
• Persistent left superior vena cava

• J. Edward Bass, Michael D. Redwine, Larry A. Kramer, Phan T. Huynh, and John H. Harris, Jr. Spectrum of Congenital Anomalies of the Inferior Vena Cava: Cross-sectional Imaging Findings. RadioGraphics 2000 20: 639-652.

• Moss and Adams’ Heart Disease in Infants, Children, and Adolescents Hugh D. Allen, Arthur J. Moss, David J. Driscoll, Forrest H. Adams, Timothy F. Feltes, Robert E. Shaddy, 2007 ISBN 0781786843

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