Distended azygos and hemiazygos vein without interrupted inferior vena cava in a case of agenesis of the ductus venosus

Abstract

A 26-year-old woman, gravida 2 para 0, was referred for a detailed scan including uterine artery Doppler ultrasound examination, as her previous pregnancy ended in the intrauterine death of twins. Uteroplacental resistance in the index pregnancy was markedly increased with bilateral notching of the uterine artery waveform. At 26 weeks detailed fetal echocardiography showed normal cardiac structures. However, a blood vessel with venous flow velocity waveforms running in parallel to the thoracic aorta, which was classified as a distended azygos vein, was detected by color Doppler ultrasound imaging (Figure 1). The possibility of a heterotaxy syndrome could be excluded due to situs solitus and a non-interrupted inferior vena cava (IVC) (Figures 2-4). Furthermore, abnormal draining of the umbilical vein (UV) directly into the abdominal part of the IVC was detected (Figures 3 and 4). This was classified as agenesis of the ductus venosus (DV) with portocaval shunt, and was similar to that described in a recently published case1, 2. Posterior to this connection a collateral venous vessel originated from the IVC, joining the dilated hemiazygos vein on the left side of the abdominal aorta. In the thorax the hemiazygos vein crossed to the right, joining the azygos vein (Figure 5), before finally running into the superior vena cava. Color Doppler ultrasound examination showing distended azygos vein (red) posterior to the thoracic aorta (blue). Ultrasound scan showing normal four-chamber view and cross-section through the thoracic aorta and azygos vein. Gray-scale ultrasound image showing direct connection of the umbilical vein to the inferior vena cava. Color Doppler image with glass-body rendering, showing connection of the umbilical vein (UV) and the inferior vena cava (IVC). Color Doppler image of the fetal thoracic region, showing the hemiazygos vein crossing from the left to the right side and joining the azygos vein. A possible complication caused by a direct connection between the UV and the IVC may be the development of high-output cardiac failure owing to chronic volume overload of the central venous system and the heart3, 4. However, in our case no signs of cardiac overload were detected. At 31 + 4 weeks the woman developed pre-eclampsia and fetal arterial blood flow redistribution indicated low resistance in the middle cerebral artery. After induction of lung maturity, a boy with a birth weight of 1550 g, Apgar scores of 7, 9 and 9 at 1, 5 and 10 min, respectively, and arterial pH 7.28 was delivered by Cesarean section. The neonatal course was uneventful. Pediatric echocardiography at the age of 10 weeks showed normal cardiac function, a closed DV and an enlarged hemiazygos vein on the left side of the abdominal aorta. The liver circulation was normal. At the time of writing, the infant was 10 months old and healthy. To our knowledge, this is the first description of a distended azygos/hemiazygos vein coexistent with a non-interrupted IVC and without association with heterotaxy syndrome. The collateral venous circulation through the hemiazygos vein in the presence of an abnormal direct connection between the UV and IVC may have resulted in a protective effect against cardiac overload. However, owing to the development of pre-eclampsia and fetal blood flow redistribution with decreasing resistance in the middle cerebral artery, a Cesarean section was indicated. We would advise longitudinal fetal monitoring with Doppler ultrasound imaging and echocardiography in similar cases. H. Hille*, R. Chaoui , S. Renz , K. Hecher?, * Lappenbergsallee 50, Hamburg, D-20257, Germany, Center for Pediatric Cardiology, Hamburg, Germany, Obstetrics and Fetal Medicine, University Medical Center, Hamburg, Germany, ? Center for Prenatal Diagnosis and Human Genetics, Berlin, Germany