Recommended Link:

Azygos continuation of Inferior Vena Cava (IVC)

Posted Sun, 01/17/2010 - 10:54 by Shweta Bhatt
Images

Fig 1.

Fig 2a

Fig 2b.

Fig 2c

Fig 3

Fig 4

Fig 5


Clinical History:

22 year-old female with chest pain.


Findings:

Fig 1. Plain radiograph of the chest shows a focal bulge at the right paratracheal region.
Fig 2 a – c. Sequential contrast enhanced CT images demonstrate an enlarged azygos arch and azygos vein. There is absent hepatic and suprahepatic portion of the IVC. The hepatic veins drain directly into the right atrium.
Fig 3. Contrast enhanced CT of the abdomen in the same patient shows mulitple splenules.
Fig 4. Coronal reconstructed CT image demonstrates an enlarged azygos vein continuing as the IVC .
Fig 5. Gray scale ultrasound of the left upper quadrant shows multiple splenules , suggestive of polysplenia.


Diagnosis:

Azygos continuation of IVC


Discussion:

The azygos vein develops from the right supracardinal vein and the proximal portion of the right posterior cardinal vein. When the right subcardinal vein does not anastomose with the right vitelline vein, the hepatic segment of the inferior vena cava is not formed. The sacrocardinal and renal segments thus shunt blood directly into the right supracardinal vein to result in the congenital anomaly of azygos continuation of the IVC. 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. Since the postsubcardinal anastomosis does not contribute to formation of the IVC, 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.

Radiographic findings:
- Focal enlargement of the azygos arch in the right tracheobronchial angle
- Prominence of retroesophageal stripe
- Bilateral left lungs and bronchi if associated with polysplenia

CT findings:
- Absence of suprarenal and hepatic segments of the IVC
- Hepatic veins drain into the right atrium
- Enlarged azygos vein drain into the posterior aspect of the SVC
- Enlarged hemiazygous vein drains into the left SVC with dilated coronary sinus
- Polysplenia (heterotaxy) : situs ambiguous, bilateral bilobed lungs with bilateral hyparterial bronchi, congenital heart disease including ASD and VSD


References / Suggested Reading:

1. Bass, JE. Spectrum of Congenital Anomalies of the Inferior Vena Cava: Cross-sectional Imaging Findings. RadioGraphics 2000; 20:639–652
2. Pomeranz, SJ, Proto AV. Azygos lobe with azygos continuation of the IVC. Chest 1986;89;447-449.
3. Pakofsky, KB, Woefel, DA. Azygos continuation of the inferior vena cava. Am J Roentgenol 1971 Oct;113(2):362-5.


Author

Shweta Bhatt, MD and Vikram S Dogra, MD

Assistant Professor (SB) and Professor (VSD) of Radiology

University of Rochester , Rochester, NY

  • Printer-friendly version