CASE 2067 Published on 13.12.2005

Hemiazygos continuation of the inferior vena cava: demonstration by contrast-enhanced MR venography

Section

Cardiovascular

Case Type

Clinical Cases

Authors

G. Giannikouris, I. Staikidou, C. Pikoulas, G. Mantzikopoulos

Patient

23 years, female

Categories
No Area of Interest ; Imaging Technique MR-Angiography
Clinical History
The patient was investigated because of repeated episodes of fainting. The preliminary chest X-ray showed mediastinal enlargement, which was shown to be an enlarged azygos vein on CT of the chest. Subsequent CT of the abdomen demonstrated the presence of a left inferior vena cava. Contrast-enhanced MR venography was performed.
Imaging Findings
The patient was investigated because of repeated episodes of fainting. The preliminary chest X-ray showed mediastinal enlargement. A CT of the chest revealed an enlarged azygos vein. Subsequent CT of the abdomen demonstrated a venous anomaly with the presence of a left inferior vena cava apparently draining into the hemiazygos and azygos veins and an absent subdiaphragmatic right inferior vena cava. Contrast-enhanced MR venography was performed (0.2ml/kg contrast, 50 sec delay time) which clearly demonstrated the direction of the flow of the left inferior vena cava into the hemiazygos-azygos system and finally via the superior vena cava into the right atrium (Figs 1-3). Absence of the infrahepatic right inferior vena cava and a hypoplastic intrahepatic segment were also evident (Fig. 2). There was a normal supradiaphragmatic segment of the right inferior vena cava draining the hepatic veins (Figs 2b,c). Additionally, anomalous drainage of the hepatic segments V and VI into the right renal vein was shown (Figs 2b,c).
Discussion
Anomalies of the inferior vena cava (IVC), the superior vena cava (SVC) and the azygos and hemiazygos veins can be asymptomatic and can be found in patients with situs inversus or in patients being investigated for other conditions.

The left IVC or transposition of the IVC occurs in 0.2-0.5% of the general population [1-3] as a result of an embryological disorder (persistence of the infrarenal part of the left supracardinal vein and regression of the infrarenal part of the right supracardinal vein).

The interruption of the IVC with hemiazygos or azygos continuation is a rare (0.6%), but well-described anomaly [4,5]. A more rare anomaly is the presence of a left IVC with hemiazygos continuation. In this situation there are three possible routes for the return of the blood to the right atrium [3]: (a) via the azygos vein to the SVC, (b) via the accessory hemiazygos and left superior intercostal veins to the left brachiocephalic vein, or (c) via the accessory hemiazygos and a persistent left SVC into the coronary sinus.

In this patient the blood return was via the hemiazygos vein to the azygos vein and through the SVC into the right atrium. Although there have been cases reported in the radiological literature of hemiazygos continuation of a left IVC, to our knowledge there has been no previous report of such a case investigated with contrast-enhanced MR venography demonstrating additional venous anomalies in the abdomen (which in this patient were the presence of a hypoplastic intrahepatic segment of the right IVC and anomalous venous drainage of the hepatic segments V and VI into the right renal vein).

IVC anomalies are most often detected incidentally. Recognition of these anomalies can be very important and can prevent diagnostic mistakes as well as problems when planning intervention procedures (placement of IVC filters, renal vein sampling) or abdominal surgery (aortic aneurysm repair, renal transplantation or donor evaluation, adrenalectomy, nephrectomy or left sympathectomy).

MR venography is a safe and reliable contrast-enhanced alternative to conventional or CT venography. The procedure is quick and simple and can be combined with phase contrast venography and flow direction studies.

Differential Diagnosis List
Hemiazygos continuation of the left inferior vena cava with additional anomalous drainage of the hepatic segments V and VI into the right renal vein
Final Diagnosis
Hemiazygos continuation of the left inferior vena cava with additional anomalous drainage of the hepatic segments V and VI into the right renal vein
Case information
URL: https://www.eurorad.org/case/2067
DOI: 10.1594/EURORAD/CASE.2067
ISSN: 1563-4086