title: Prenatal diagnosis of a variant of the azygos venous system.
abstract: BACKGROUND
  The azygos venous system consists of the azygos vein on the right side and the hemiazygos and accessory hemiazygos on the left side. The azygos vein runs through the abdominal cavity along the right side of the vertebral bodies, in a cranial direction, passes through the diaphragm and reaches the mediastinum, where it forms the arch of the azygos which flows into the superior vena cava. Along its course, the azygos vein communicates with the intercostal veins on the right, the hemiazygos vein that collects blood from the left lower intercostal veins, and accessory hemiazygos vein that drains into the left upper intercostal veins. The last two, at the level of the seventh thoracic vertebra, unite and end in the azygos vein. The accessory hemiazygos vein is normally included in the length between T4 and T8. The embryological origin of the accessory hemiazygos vein is the result of an expansion in the direction of the cranial hemiazygos vein, which comes from the left upper sovracardinale vein (Dudiak et al. in Semin Roentgenol 24(1):47-55, 1989; Radiographics 11(2):233-246, 1991; Webb et al. in Am J Roentgenol 139(1):157-161, 1982).
  
  
  RESULTS
  This case report describes a rare variant of azygos vein system identified in prenatal diagnosis and confirmed by postnatal ultrasonography.
  
  
  CONCLUSIONS
  The observation of the patient has excluded hemodynamic alterations associated with vascular anomaly.
authors: Department of Sciences for Health Promotion and Mother and Child Care, Palermo University, Palermo, Italy.
authors: Clelia
authors: C
authors: Lo Verso
authors: U.O.S. Fetal Medicine and Prenatal Diagnosis, A.O. Hospital Villa Sofia-Cervello , Palermo, Italy.
authors: Valentina
authors: V
authors: Cigna
authors: U.O.S. Fetal Medicine and Prenatal Diagnosis, A.O. Hospital Villa Sofia-Cervello , Palermo, Italy.
authors: Gianfranca
authors: G
authors: Damiani
authors: Department of Sciences for Health Promotion and Mother and Child Care, Palermo University, Palermo, Italy.
authors: Laura
authors: L
authors: Lo Verso
authors: U.O. of Neonatology and NICU, A.O. Hospital Villa Sofia-Cervello, Palermo, Italy.
authors: Rossella
authors: R
authors: Conti
authors: U.O. of Neonatology and NICU, A.O. Hospital Villa Sofia-Cervello, Palermo, Italy.
authors: Vincenzo
authors: V
authors: Duca
keywords: Accessory hemiazygos vein; Azygos vein; Hemiazygos vein; Prenatal diagnosis; Variants