Inferior vena cava (IVC) anomalies, such as the absence of an intra-hepatic IVC or IVC hypoplasia, are rare. Usually, these anomalies are asymptomatic and cause few clinical issues. We herien report a 53-year-old woman with IVC anomalies who demonstrated both azygos and portal vein system continuation. Over time, this resulted in gradually progressive portal hypertension due to abnormal hemodynamics. The increased inflow from the IVC to the portal vein system for an extended time may contribute to the development of portal hypertension without liver cirrhosis.