Objective
Report our experience in prenatal diagnosis of 11 cases of interrupted inferior vena cava, summarize the clinical significance and implications of this variant.
Study Design
Retrospective analysis of 11 fetuses diagnosed with interrupted inferior vena cava, of 55,457 pregnant women who underwent extensive fetal anomaly scan during 20 years.
Results
Eight of the 11 fetuses with interrupted inferior vena cava had a completely normal outcome. One had also normal outcome but abnormal function of the spleen. One had multiple abnormalities, and 1 case was lost to follow up.
Conclusion
The incidence of IIVC is 1:5000. In the vast majority (90%) of the cases, it is an isolated variant not associated with isomerism or fetal anomalies. In all the cases of isolated interrupted inferior vena cava, the outcome is favorable. In 10% of isolated interrupted inferior vena cava, abnormal function of the spleen may be detected after delivery, necessitating antipneumococcal vaccination.
Inferior vena cava interruption with azygos or hemiazygos vein continuation is considered to be a rare congenital anomaly, especially when not associated with congenital heart disease.
Its prevalence is 0.6-2% in patients with congenital heart disease and less than 0.3% among otherwise normal fetuses. This malformation results from a connection failure between the right subcardinal vein and the right vitelline vein. Consequently, the venous blood from the caudal part of the body reaches the heart via the azygos or hemiazygos vein through the superior vena cava. Systemic venous flow beyond this point is compensated by the dilated azygos and hemiazygos arch. Interrupted inferior vena cava (IIVC) is usually associated with visceral heterotaxy and cardiac anomalies. It might be the only sonographic clue to abnormal splenic function (in cases of isolated polysplenia). During embryogenesis, the inferior vena cava (IVC) is made up of the hepatic, prerenal, renal, and postrenal segments, which by segmental fusion, regression, and midline anastomoses form the IVC. Most of the published literature addresses IIVC as a marker of left isomerism, and in most publications, the 2 entities are associated. The only report of 2 cases with good prognosis was that of Celentano et al who concluded that isolated IIVC can be a vascular malformation without pathologic consequences.
We report in this article our experience in cases of IIVC prenatally diagnosed and summarize the clinical significance and application of this vascular variant.
Materials and Methods
Over the last 20 years, an extensive fetal anatomy scan was performed in 55,457 consecutive pregnancies. The study population consisted of private, self-referred patients who were interested in early sonographic detection of anomalies. Most of these sonographic scans were performed by transvaginal sonography (TVS) at 14-16 weeks’ gestation or by abdominal sonography at 19-24 weeks. All examinations were performed by the same sonologist, who used an ESI 1000, ESI 3000 and Philips IU 22 ultrasound machines (Philips, Andover, MA).
For all the 11 described fetuses with IIVC, a detailed echocardiography and an extensive sonographic fetal anomaly scan were performed. The IVC was carefully examined in each of these 11 fetuses as a part of cardiac echography, in a sonographic right parasagittal section at its entrance to the right atrium. The main sonographic sign for the diagnosis of an absent IVC at its entrance to the right atrium was failure to visualize it using B-mode and power-angio sonograms. Secondary, auxiliary evidence to an IIVC was the visualization of a pseudovascular arch formed by the dilated azygos arch at the entrance of the azygos vein to the superior vena cava (SVC), posterior to the trachea, in a transverse section of the fetal thorax ( Figure 1 ). Similarly, this pseudovascular arch formed by the dilated azygos vein was also demonstrated in each case in a paraaortic sagittal section, visualizing the dilated azygos arch, parallel to the aorta ( Figure 2 ). None of our cases of IIVC had hemiazygos continuation, all had azygos continuation.
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