Azygous continuation of the IVC and hepatic steatosis
A 45 years old male presented for CT scan of the abdomen for 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 infra-renal IVC is seen on the left side. It drains both renal veins and it ascends to join the hemi-azygous vein, which drains into the azygous vein and this ascends in its usual retro-crural course to the chest.
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Imaged showed the infra-renal IVC is seen on the left side (long white arrows). It drains both renal veins (long red arrows) and it ascends to join the hemi-azygous vein (short red arrows), which drains into the azygous vein and this ascends in its usual retro-crural 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 2 3.
This anomaly results from failure of right sub-cardinal-hepatic anastomosis with atrophy of right sub-cardinal vein and shunting of blood from supra-cardinal-sub-cardinal anastomosis to cranial portion of supra-cardinal vein (retro-crural azygos vein) 2.
Imaging findings include: hepatic veins drain into right atrium. Renal veins drain into azygous (or hemi-azygous). This anomaly usually occurs with a right infra-renal IVC with azygos/hemi-azygos continuation (4), but it may also occur with other two variants:
(1) Left infra-renal IVC with azygos/hemi-azygos continuation 5 (as in this case).
(2) Double infra-renal IVCs with two possibilities: EITHER both IVCs join at the renal level and continue as azygos vein) 6 OR (the right IVC continues as the azygos vein and the left one continues as the hemi-azygos vein) 7.
The clinical importance of this anomaly is in misinterpretation as right para-tracheal mass or retro-crural adenopathy, in being associated with heterotaxy syndromes and other congenital heart diseases and in pre-operative knowledge of the anatomy prior to planning cardio-pulmonary 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.