Prenatal diagnosis of isolated interruption of inferior vena cava with continuation of azygos vein

Congenital diseases of the inferior vena cava are uncommon. Isolated congenital interruption of the inferior vena cava with continuation of azygos vein could be considered part of the group of venous return anomalies. In these cases, it drains into the heart through azygos vein. It is considered a prenatal ultrasound marker, since the greatest importance of this anomaly is its association with complex cardiac defects. Therefore, its finding requires a detailed ultrasound evaluation of the heart and fetal internal organs. Ultrasound diagnosis is simple if the characteristic "double vessel" sign is observed of abdomen or thorax axial section. We present a case of prenatal diagnosis of isolated interruption of inferior vena cava with continuation of azygos vein as a lonely finding during routine prenatal ultrasound, confirmed by postnatal evaluation. In evaluation of venous vasculature, in the sagittal midplane of the ultrasound evaluation of the thorax and fetal abdomen, a parallel vessel was observed, adjacent and posterior to the aorta that communicated the kidney and the superior vena cava. Detailed sonographic examination of the fetal anatomy could not demonstrate other abnormalities. After 9 months of follow-up, infant develops normally.