Application of spatio-temporal image correlation combined with high-difinition flow in demonstration of fetal azygos vein during the second gestation
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Objective To evaluate the feasibility of demonstrating the fetal azygos vein by spatio-temporal image correlation(STIC) combined with high-difinition flow(HD) imaging during the second gestation. Methods Two hundred fetuses between March 2013 to November 2013 were divided into 2 groups. In study group, STIC and HD were applied to demonstrate the azygos vein on the fetal thoracoabdominal para-midsagittal view, the relationship between the azygos vein and thoracic aorta, the shape, location and modality of archof azygos vein which joins the superior vena cava were observed after post processing.And two-dimensional ultrasound and color Doppler flow imaging(CDFI) was applyed in the control droup. Results 96/100 of the azygos vein was successfully demonstrated in the study group with the rate of 96%,while 85/100 was successfully demonstrated in the control group with the rate of 85%. According to the relationship of the azygos vein with the spine,the proportion of the right type,middle type and left type of the azygos vein was 26.0%,33.9%,40.1%. The azygos vein parallels with the thoracic aorta upside to the level of superior vena cava,and bends forward and joins the superior vena cava. In one case with hepatic segment of inferior vena cava interruption, wthe azygos vein was dilated with similar diameter to the thoracic aorta. Conclusion It is feasible to demonstrate the azygos vein by STIC combined with HD. The diameter, shape, location and manner of azygos vein can be observed.It can hint the diagnosis of disease that results in expansion of azygos vein. It is better than two-dimensional ultrasound combined.Keywords:
Azygos vein
Thoracic aorta
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Objectives To establish fetal azygos vein and descending aorta sonographic Z score formulas based on femur length and gestational age and to determine the value of azygos vein diameter variation for potential use in the diagnosis of fetal venous malformations related to the azygos vein. Methods A total of 452 healthy singleton fetuses and 25 fetuses with venous malformations related to the azygos vein underwent prenatal sonography in this retrospective study. Azygos vein and descending aorta diameters were measured offline after spatiotemporal image correlation volume acquisition. Normal azygos vein and descending aorta Z score formulas were constructed for these measurements based on femur length by performing standard regression analysis followed by weighted regression of absolute residual values. The azygos vein‐to‐descending aorta ratio was calculated. Three parameters were compared between venous malformations related to the azygos vein and healthy fetuses. Results Azygos vein and descending aorta Z score formulas were constructed. Both showed a positive linear correlation with femur length ( r = 0.79 and 0.90, respectively; P < .01) and gestational age ( r = 0.79 and 0.91; P < .01). The azygos vein Z scores and azygos vein‐to‐descending aorta ratios of fetuses with malformations were significantly higher than those of healthy fetuses ( P < .01). In the abnormal group, 96.0% of azygos vein Z scores (24 of 25) were greater than ±2, and 96.0% of azygos vein‐to‐descending aorta ratios (24 of 25) were greater than the 95% confidence interval. Conclusions The azygos vein Z score formulas we developed can provide a quantitative basis for prenatal screening of venous malformations related to the azygos vein. Azygos vein dilatation and an abnormal azygos vein‐to‐descending aorta ratio may contribute to increasing the recognition of venous malformations involving the azygos vein.
Azygos vein
Descending aorta
Fetal echocardiography
Thoracic aorta
Femoral vein
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Objective To discuss CT manifestations of azygos vein and to evaluate the clinical significance of azygos vein abnormalities.Materials and Methods One hundred normal thoracic CT exams (study group) were randomly selected. The diameter and enhanced pattern of the azygos vein were measured and observed. Nine patients with abnormal signs of azygos vein, including portal hypertension (n=4), occlusion of SVC (n=4) and obstruction of left brachiocephalic vein trunk (n=1), were used as control group. Results In study group, the diameter of azygos vein was 6～10mm, displaying mild to moderate enhancement at 45 seconds after contrast injection, with CT values slightly lower than that of the aorta at the same level. The diameter of azygos vein over 10～12mm should be regarded as abnormal dilatation. When the enhanced CT value of azygos vein was larger than that of the aorta, it should be taken as a sign of abnormal enhancement. Conclusion Dilated azygos vein is commonly seen in the presence of collateral formation between the azygos vein and the portal vein, SVC or IVC. Abnormal enhancement of azygos vein is usually due to the obstruction of SVC, which leads to an abundant flow of contrast media directly into azygos vein. The observation of azygos vein is helpful for judging the site and extent of vascular disease, for assessing the involvement of the portal vein, SVC and IVC, and for early detecting the occult diseases.
Azygos vein
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The azygos system of veins varies greatly in their mode of origin, course, tributaries, anastomoses and termination. These deviations result predominantly due to its complex embryological development. Azygos venous system develops as right and left aygos venous lines dorsolateral to the aorta. Right azygos venous line develops into vertical part of azygos vein and left one gives rise to a set of longitudinally arranged veins which develops into superior or accessory hemiazygos veins and inferior hemiazygos vein. These are connected by subcentral/ transvertebral veins which vary extremely. The number of such transvertebral veins has been reported from zero to five in the previous literature. In the present case, a continous left azygos venous line was reported which drained into right azygos vein through a single transvertebral connection, thus there is only one transvertebral vein and the left azygos line is not divided into superior and inferior hemiazygos veins. Anatomical knowledge of such variations is important for a clinician while doing mediastinal surgery or to interpret CT/ MRI images.
Azygos vein
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Azygos vein
Neuroradiology
Brachiocephalic vein
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Thirty embalmed adult human cadavers irrespective of age, sex and cause of death, were selected for this study over a period of one year to determine the azygos vein formation and drainage patterns. This study revealed four varieties regarding azygos vein formation. In twenty two cases (73.3%), the azygos vein formed by the confluence of the right subcostal and right ascending lumbar vein. It formed by the right subcostal vein with a contribution from the inferior vena cava (IVC) in three cases (10.0%) while, it formed by the right and left subcostal veins in three cases (10.0%) and in two cases (6.7%) formed by the right subcostal vein only. Moreover, in twenty three cases (76.67%), the azygos vein showed usual course and tributaries. Five cases (16.67%) revealed midline azygos vein with independent left lower eight posterior intercostal and subcostal veins. One case (3.33%) showed (H) shape azygos system. Independent double azygos veins were found in one case (3.33%). Based on the results, the azygos vein can take different developmental variations. Such variations are important in mediastinal surgery, imperative for reporting radiologists and have clinical importance. Variations in the formation and drainage pattern of the azygos vein are not clearly described in the literature. In this study the possible causes of these types of variations are discussed in view of the embryological development.
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Alterations in CT mediastinal anatomy produced by an azygos lobeJM Speckman, G Gamsu and WR WebbAudio Available | Share
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The venous system variations are generally explained on the basis of their embryological development. Tributaries of the azygos venous system varies greatly. Variations of azygos venous system and especially of the hemiazygos veins are not clearly described in the literature. In this case, the azygos vein instead of lying on the right side of the vertebral column was in the midline of posterior mediastinum. The left azygos venous line was ill defined and lower left posterior intercostal veins were opening independently into the azygos vein. The left superior intercostal vein was opening into the azygos vein. The accessory hemiazygos vein was ill defined. The origin and termination of the azygos venous system was found normal. These variations are discussed in view of its embryological development. Clinically these variations should be kept in mind while doing mediastinal surgery of large vessels.
Azygos vein
Venous malformation
Posterior mediastinum
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