Severe anaemia, pulmonary hypertension and dilatation of the right heart’s chambers.
CXR: increased interstitial pattern.
Chest-CT without contrast: incidental adrenal lesion (Fig. 1-2).
Abdominal-CT with/without contrast medium: solid nodular lesion in the right adrenal fossa (34x33x57 mm), close to hepatic S1 with evidence of a subtle fat cleavage (Fig. 3-7).
At MRI the right adrenal gland appears regular in morphology, size and signal intensity. In proximity to its medial border an expansive lesion is evident, that on the baseline T1w and T2w sequences is characterised by signal intensities similar to the upper and lower lumen of the IVC, in continuity with the IVC lumen and right renal vein, without diffusion restriction on the DWI sequences (Fig. 8-11). Dynamic study before and after automatic i.v. injection of Gadobenate Dimeglumine (1.0 mml/ml - 8 ml@2 ml/sec+ 20 ml of saline injection) shows its vascular nature, allowing to classify it as a pseudo-aneurysmatic venous dilation (Fig. 12). Moreover, a thoracic continuation of the azygos vein is demonstrated, which appears hypertrophic due to preferentially abdominal outflow. The confluence of the hepatic veins and the atrial outlet of the IVC appear regular. The patient was also evaluated with US/colour Doppler US for consensual assessment (Fig. 13-14).
The IVC develops between the 6th-8th gestation weeks, following the formation of anastomosis and regression of 3 pairs of veins: sub-cardinal, supra-cardinal and post-cardinal [1, 3].
Nine anatomical variants of IVC and renal veins have been described [1, 2, 4] (Tab 1).
The azygos continuation of the IVC has also been termed absence of the hepatic segment of the IVC with azygos continuation . There is a failure to form the right subcardinal–hepatic anastomosis, with resulting atrophy of the right subcardinal vein. Consequently, blood is shunted from the supra-subcardinal anastomosis through the retrocrural azygos vein, which is partially derived from the thoracic segment of the right supracardinal vein. The renal portion of the IVC receives blood return from both kidneys and enters the thorax as the azygos vein. The azygos joins the SVC at the normal location in the right paratracheal space. The hepatic segment is ordinarily not truly absent; rather, it drains directly into the right atrium.
Azygos continuation of the IVC has become increasingly recognised in otherwise asymptomatic patients since the advent of cross-sectional imaging. It is important to diagnose the enlarged Azygos vein at the SVC confluence and in the retrocrural space to avoid misdiagnosis as a right-sided paratracheal mass or retrocrural adenopathy. Moreover, preoperative knowledge of vascular anatomy is fundamental for a correct planning of cardiopulmonary bypass and to avoid difficulties in cardiac catheterisation procedures.
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 2. Kellman GM, Alpem MB, Sandler MA et-al. (1998) Computed tomography of vena caval anomalies with embryologic correlation. Radiographics 8 (3): 533-56 (PMID: 3380993)
 3. Balzer KM, Pillny M, Luther B, Grabitz K, Sandmann W. (2002) . Spontaneous rupture of collateral venous aneurysm in a patient with agenesis of the inferior vena cava: a case report. J Vasc Surg 36(5):1053-7 (PMID: 12422117)
 4. Sheth S, Fishman EK. (2007) Imaging of the inferior vena cava with MDCT. AJR Am J Roentgenol 189(5):1243–1251 (PMID: 17954667)
 5. Ginaldi S, Chuang VP, Wallace S. (1980) Absence of hepatic segment of the inferior vena cava with azygos continuation. J Comput Assist Tomogr 4:112-114 (PMID: 7354162)
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