Impressive dilatation of azygos vein due to congenital anomaly of inferior vena cava.

A right-sided thoracotomy was performed for pulmonary metastases in an asymptomatic patient. Preoperative computed tomography (CT) scan showed partial thrombosis or agenesis of the inferior vena cava (Fig. 1). Intra-operatively, an impressive dilation of the azygos vein was noted (Fig. 2). The azygos vein or superior vena cava was not invaded by tumour. Fig. 1. Preoperative thoracic CT scan showing specific venous anomalies: absence of inferior vena cava and dilated azygos vein prevertebrally, not filled with contrast. A lung metastasis is present in the right lower lobe. Fig. 2. Intraoperative view showing impressive dilatation of azygos vein secondary to absence of the inferior vena cava. In case of invasion of the azygos vein or superior vena cava, radical resection and reimplantation in the right atrium would have been required.