Azygos continuation of the IVC
Evaluation of hepatic steatosis with suspicious focal lesion depicted during US examination
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Images showed diffuse fatty infiltration of the liver, with no detectable focal lesions.
The infrarenal IVC is seen on the left side. It drains both renal veins and it ascends to join the hemiazygos vein, which drains into the azygos vein and this ascends in its usual retrocrural course to the chest.
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Infrarenal IVC is seen on the left side (long white arrows). It drains both renal veins (long red arrows) and it ascends to join the hemiazygos vein (short red arrows), which drains into the azygos vein and this ascends in its usual retrocrural course to the chest (long green arrows).
The reported incidence of this anomaly is estimated to be 0.6-2% of patients with congenital heart diseases and less than 0.3% in otherwise normal individuals 1-3.
This anomaly results from failure of right subcardinal-hepatic anastomosis with atrophy of right subcardinal vein and shunting of blood from supracardinal-subcardinal anastomosis to cranial portion of supracardinal vein (retrocrural azygos vein) 2.
Imaging findings include: hepatic veins drain into right atrium. Renal veins drain into azygos (or hemiazygos). This anomaly usually occurs with a right infra-renal IVC with azygos/hemiazygos continuation 4, but it may also occur with other two variants:
- left infrarenal IVC with azygos/hemiazygos continuation 5 (as in this case).
- double infrarenal IVCs with two possibilities: either both IVCs join at the renal level and continue as the azygos vein) 6 or (the right IVC continues as the azygos vein and the left one continues as the hemiazygos vein) 7.
The clinical importance of this anomaly is the risk of misinterpretation of it as a right paratracheal mass or retrocrural adenopathy, in being associated with heterotaxy syndromes and other congenital heart diseases and in preoperative knowledge of the anatomy prior to planning cardiopulmonary bypass and to avoid difficulties in catheterizing the heart 8,9.
- 1. Dähnert W. Radiology Review Manual. LWW. (2011) ISBN:1609139437. Read it at Google Books - Find it at Amazon.
- 2. Bass JE, Redwine MD, Kramer LA et-al. Spectrum of congenital anomalies of the inferior vena cava: cross-sectional imaging findings. Radiographics. 2000;20 (3): 639-52. doi:10.1148/radiographics.20.3.g00ma09639 - Pubmed citation.
- 3. Mehta AJ, Kate AH, Gupta N et-al. Interrupted inferior vena cava syndrome. J Assoc Physicians India. 2013;60: 48-50. Pubmed citation.
- 4. Vijayaraghavan SB, Raja V, Chitra TV. Interrupted inferior vena cava and left-sided subrenal inferior vena cava: prenatal diagnosis. J Ultrasound Med. 2003;22 (7): 747-52. Pubmed citation.
- 5. Amato M, Biondetti PR. Left inferior vena cava, with hemiazygos continuation and atypical flow into the superior vena cava. A case report. Radiol Med. 2001;99 (6): 474-5. Pubmed citation.
- 6. Esposito S, Mansueto G, Amodio F et-al. Duplication of the vena cava inferior with a continuation into the vena azygos. A report of a rare case. Minerva Chir. 1999;54 (4): 261-5. Pubmed citation.
- 7. Mayo J, Gray R, St Louis E et-al. Anomalies of the inferior vena cava. AJR Am J Roentgenol. 1983;140 (2): 339-45. doi:10.2214/ajr.140.2.339 - Pubmed citation.
- 8. Ginaldi S, Chuang VP, Wallace S. Absence of hepatic segment of the inferior vena cava with azygous continuation. J Comput Assist Tomogr. 1980;4 (1): 112-4. Pubmed citation.
- 9. Mazzucco A, Bortolotti U, Stellin G et-al. Anomalies of the systemic venous return: a review. J Card Surg. 1992;5 (2): 122-33. Pubmed citation.