Infrahepatic inferior caval and azygos vein formation in mammals with different degrees of mesonephric development.

Controversies regarding the development of the mammalian infrahepatic inferior caval and azygos veins arise from using topography rather than developmental origin as criteria to define venous systems and centre on veins that surround the mesonephros. We compared caudal-vein development in man with that in rodents and pigs (rudimentary and extensive mesonephric development, respectively), and used Amira 3D reconstruction and Cinema 4D-remodelling software for visualisation. The caudal cardinal veins (CCVs) were the only contributors to the inferior caval (IVC) and azygos veins. Development was comparable if temporary vessels that drain the large porcine mesonephros were taken into account. The topography of the CCVs changed concomitant with expansion of adjacent organs (lungs, meso- and metanephroi). The iliac veins arose by gradual extension of the CCVs into the caudal body region. Irrespective of the degree of mesonephric development, the infrarenal part of the IVC developed from the right CCV and the renal part from vascular sprouts of the CCVs in the mesonephros that formed 'subcardinal' veins. The azygos venous system developed from the cranial remnants of the CCVs. Temporary venous collaterals in and around the thoracic sympathetic trunk were interpreted as 'footprints' of the dorsolateral-to-ventromedial change in the local course of the intersegmental and caudal cardinal veins relative to the sympathetic trunk. Interspecies differences in timing of the same events in IVC and azygos-vein development appear to allow for proper joining of conduits for caudal venous return, whereas local changes in topography appear to accommodate efficient venous perfusion. These findings demonstrate that new systems, such as the 'supracardinal' veins, are not necessary to account for changes in the course of the main venous conduits of the embryo.

Development of the human infrahepatic inferior caval and azygos venous systems.

Differences in opinion regarding the development of the infrahepatic inferior caval and azygos venous systems in mammals centre on the contributions of 'caudal cardinal', 'subcardinal', 'supracardinal', 'medial and lateral sympathetic line' and 'sacrocardinal' veins. The disagreements appear to arise from the use of topographical position rather than developmental origin as criterion to define separate venous systems. We reinvestigated the issue in a closely spaced series of human embryos between 4 and 10 weeks of development. Structures were visualized with the Amira(®) reconstruction and Cinema4D(®) remodelling software. The vertebral level and neighbouring structures were used as topographic landmarks. The main results were that the caudal cardinal veins extended caudally from the common cardinal vein between CS11 and CS15, followed by the development of the subcardinal veins as a plexus sprouting ventrally from the caudal cardinal veins. The caudal cardinal veins adapted their course from lateral to medial relative to the laterally expanding lungs, adrenal glands, definitive kidneys, sympathetic trunk and umbilical arteries between CS15 and CS18, and then became interrupted in the part overlaying the regressing mesonephroi (Th12-L3). The caudal part of the left caudal cardinal vein then also regressed. The infrarenal part of the inferior caval vein originated from the right caudal cardinal vein, while the renal part originated from subcardinal veins. The azygos veins developed from the remaining cranial part of the caudal cardinal veins. Our data show that all parts of the inferior caval and azygos venous systems developed directly from the caudal cardinal veins or from a plexus sprouting from these veins.

Microscopic magnetic resonance imaging of the thoracic venous system in rats with congenital diaphragmatic hernia.

BACKGROUND/AIM: Infants and rats with congenital diaphragmatic hernia (CDH) have malformations of the heart and the great arteries caused by neural crest (NC) dysregulation during embryogenesis. Abnormally narrow jugular veins have been found in babies during cannulation for ECMO. However, the venous system has not been examined in depth so far. We hypothesized that abnormal patterning and/or size of the thoracic veins could occur in rats with CDH. This hypothesis was tested by microscopic magnetic resonance imaging (MMRI), a high-resolution tool able to detect subtle changes of vessels in small animals. MATERIAL/METHODS: Fetuses from pregnant rats fed either 100 mg i.g. nitrofen or vehicle on E9.5 were recovered near term. A 7 T MMRI system with a coronal multislice fast spin echo sequence allowed diagnosis of CDH (n = 19), and T2 SE high-resolution sequences made assessment of the pattern and width of cervico-thoracic veins possible. Values were corrected for body size by dividing them by the length of thoracic vertebrae T3-T5. The results in nitrofen and control (n = 11) groups were compared by non-parametric tests (*p < 0.05). RESULTS: Congenital diaphragmatic hernia fetuses were smaller than controls (4.5 ± 0.26 vs. 5.3 ± 0.2 g*). The widths (corrected for body size) of left external, both innominate, right superior vena cava and azygos veins were significantly smaller in CDH rats than in controls. CONCLUSIONS: The cervico-thoracic veins are normally patterned but abnormally narrow (except the internal jugulars) in rats with CDH. The same embryonic NC dysregulation that accounts for cardiovascular malformations could also explain these venous anomalies in CDH.

Unusual fibrous band on the left aspect of the aortic arch.

During dissection of a 63-year-old female cadaver, a firm ribbon-like band was found on the left aspect of the aortic arch. Careful dissection showed that the band (6 cm long, 8 mm wide, 2 mm thick) connected the left superior intercostal vein with the accessory hemiazygos vein. Histological examination showed the fibrous structure of the band and showed the presence of a thread-like vascular lumen. The topography and venous connections of the band indicated its origin from persistence of the embryonic anastomosis between the left superior intercostal and accessory hemiazygos veins. This anastomosis derives from the rostral portion of the supracardinal vein that usually regresses on the left side but forms the terminal arch of the azygos vein on the right side. The severe atherosclerosis present in this patient at the level of the aortic arch may have enhanced the effects of arterial pressure on the adjacent venous anastomotic vessel causing reduction of blood flow and progressive fibrosis. The persistence of this venous anastomosis and its possible age-related fibrosis may have clinical relevance in central venous catheter placement.

Variability of the azygos vein system in human foetuses.

The aim of the study was to examine the variability of the azygos vein system and to determine the location of the veins with reference to the vertebral midline and the skeletopy of their termination. The research material consisted of 32 human foetuses (14 male, 18 female) from 21(st) to 24(th) week of intrauterine life, fixed in 10% neutral formalin solution. Conventional anatomical - radiographic methods were used. 5 different configurations of the azygos vein system were found. In the 1(st) configuration there were 3 azygos veins, with both the left side veins, the hemiazygos vein (HV) and the hemiazygos accessory vein (HAV), joining the azygos vein (AV) separately. In the 2(nd) configuration the HV and the HAV were joined to the AV together. In the 3(rd )configuration the HAV was missing, and the 4(th) to 8(th) left intercostal veins were joined to the AV separately. In the 4(th) configuration the HV was missing. In the 5(th) configuration there was the AV only, which coursed along the vertebral midline. In these 4 configurations (1-4) the AV was located on the right side (90.6%) and in the 5(th) configuration the AV was located in the vertebral midline. The termination of the AV projected mostly on Th(4) (81.25%). The junction of the HV and the AV was found the most frequently at Th(8) (35.7%), and the junction of the HAV and AV most frequently at Th(4) (41.6%).

Aberrant left brachiocephalic vein: CT imaging findings and embryologic correlation.

Computed tomography was utilized to evaluate aberrant left brachiocephalic vein (ALBCV), an infrequently discussed congenital vascular anomaly among Chinese people. Associated vascular variation and possible embryonic correlation are discussed. Since 1990, a total of 14 cases of ALBCV have been reported in patients receiving CT scan of chest, and was mainly an incidental diagnosis. One case was confirmed angiographically and two others were confirmed by magnetic resonance imaging. Emphasis was placed on the entry of the azygos vein into the superior vena cava (SVC), the length of the SVC, and the presence of other cardiovascular abnormalities. Of the 14 cases of ALBCV, the level of azygos vein entry was higher than the origin of the SVC in 7 cases: 4 were approximately the same level and 3 were lower. The average length of the SVC was approximately 5. 6 cm shorter than that of the general population, which is approximately 7.0 cm. Three cases had associated vascular anomaly. Most cases of ALBCV had azygos vein drainage level higher than or equal to the origin of the SVC. Right-sided aorta is one of the causes giving rise to the ALBCV during embryonic development. The CT scan remains a definitive diagnostic modality for ALBCV.

Partial agenesis of the azygos vein: a case report.

In the cadaver of an 86 year old man the inferior segment of the azygos vein could not be found. Furthermore, a normally developed hemiazygos vein drained the right and left intercostal veins from T 10 to T 6. This vessel finally curved towards the right to reach the superior vena cava after having drained the right superior intercostal veins. The left superior intercostal vein ended in a short vessel draining into the left brachiocephalic vein. This condition may be represented in a standard chest radiograph by the so-called "aortic nipple". Agenesis of the azygos vein, suspected because of the presence of this radiological sign, should be confirmed in the living by means of computerized tomography. This can clarify the anatomy of the mediastinal vessels precisely. Embryological pattern of the azygos system accounting for its possible defects is discussed.

Left atrial isomerism detected in fetal life.

Left and right atrial isomerism, comprising congenital heart defects with disturbances in normal left-right asymmetry, are phenotypically distinct after birth, although animal models suggest a common embryologic origin. We postulated that the prenatal phenotype may indeed be similar in both syndromes but that differential fetal loss is responsible for the distinct postnatal phenotypes. Distinctive fetal echocardiographic features of these syndromes have not been described in detail. We therefore sought markers of left atrial isomerism that could be recognized prenatally by echocardiography and compared our results with postnatal data to identify unique intrauterine features. We reviewed 10 cases at our center and 28 published cases of cardiac malformations with atrial isomerism detected by fetal echocardiography. Postnatal imaging and autopsies provided definitive diagnoses. Ninety-five percent of cases exhibited left atrial isomerism and formed the primary study population. Echocardiographic markers included a large azygos continuation of an interrupted inferior vena cava, atrioventricular block with structural heart disease, and viscerocardiac heterotaxy. At least 1 of these markers was seen in all of our center's cases. The incidences of most cardiac lesions detected prenatally were similar to those detected postnatally. However, although the incidences of atrioventricular septal defect and pulmonary outflow obstruction in live births were 50% and 45%, respectively, they were found much more frequently among stillbirths (80% each). In summary, we identified key fetal echocardiographic features highly sensitive for left atrial isomerism. Fetal loss selects against certain lesions such as atrioventricular septal defect. The spectrum of cardiac disease suggests a greater primitivity of the fetal heart than previously shown; the typical cardiac phenotypes are closer to right atrial isomerism than are their extrauterine presentations.

[Development of the ascending lumbar and azygos veins in human embryogenesis]. / Razvitie voskhodiashchei poiasnichnoi i neparnoi ven v émbriogenezecheloveka.

The ascending lumbar and azygos veins make a single magistral, but with different topography in the abdominal and thoracic cavities. The former runs more dorsolateral than the sympathetic trunk, and the latter--more ventromedial. These vessels are of different origin in human embryogenesis. The ascending lumbar vein develops from supracardinal veins of the abdominal cavity, that unite the dorsomedial tributaries of the postcardinal vein. The supramesonephral (thoracic) part of the latter makes the azygos vein trunk. Its beginning in the form of a plexus is determined by anastomosing supracardinal, postcardinal and mesocardinal veins. The mesocardinal vein serves as a longitudinal anastomosis for veins, connecting medial tributaries of the postcardinal vein. Differential peculiarities of its basin over the whole length and topographic peculiarities of the ascending lumbar and azygos veins depend on growth specificity of kidneys and adrenals, as well as on other organs in human embryogenesis.

[Congenital anomaly of the inferior vena cava with hemiazygos continuation. Ultrasonic diagnosis]. / Anomalie congénitale de la veine cave inférieure avec continuation hémi-azygos. Diagnostic échographique.

Congenital anomaly of the inferior vena cava with hemiazygos continuation: ultrasonic diagnosis. We report a case of agenesis of the retro-hepatic segment of the inferior vena cava in an asymptomatic 18 year old woman, found on a routine chest-ray. This rare illness was suspected on the findings of conventional radiology and was assessed by ultrasonography that shows direct termination of hepatic veins in the right auricle, and the hemi-azygos vein behind the aorta. Our radiological and ultrasonographic findings are confirmed by the literature. In the absence of any clinical signs, CT-scan and MR Imaging were note used in investigations. Nevertheless their usefulness has been extensively reported by many authors. Cavography remains useful before surgery.

Congenital interruption of the inferior vena cava.

In the usual form of interruption of the inferior vena cava (IVC), the post-renal IVC continues as the azygos and hemiazygos vein. We report a patient with complete interruption of the IVC in whom no direct continuity existed between the IVC and the azygos system. Connection between these two systems was via the vertebral plexus and ascending lumbar veins. Associated venous malformations included bilateral azygos veins and anomalous connection of pulmonary and hepatic veins.

Isolated azygos continuation of the inferior vena cava.

Our case of azygos continuation of the inferior vena cava is very rare because there was no associated heart disease or abdominal situs inversus. The diagnosis of this anomaly of the inferior vena cava should be suspected by observation of a dilated azygos vein on the chest roentgenogram and confirmed by venography.

[Absence of the vena cava inferior during simultaneous absence of the left kidney in a human fetus]. / "Fehlen" einer unteren Hohlvene bei gleichzeitigem Fehlen der linken Niere bei einem menschlichen Foeten

Atypical pattern of inferior cava (human embryo, sex: male, age: 6 month) is described. The left kidney is absent. The pelvis of the right kidney send two ureters to bladder. Pars hepatica of normal V. cava inferior is missed. Blood transport is formed by a vessel lateral of left suprarenal gland. This vessel is penetrating through pars lumbalis of diaphragm to thorax, goes in analogy to V. hemiazygos later to V. hemiazygos accessoria and flows into the right atrium.