Congenital Absence of the Inferior Vena Cava With Azygos Continuation.

Interruption of the inferior vena cava (IVC) with azygos continuation is a rare congenital anomaly resulting from abnormal embryologic development of the venous system. Although frequently associated with polysplenia and other visceral or cardiovascular malformations, many cases remain asymptomatic. Recognition of this variant is important, as it may mimic pathological masses on imaging and complicate procedures requiring central venous access. An 80-year-old woman presented with progressive functional decline following a fall. Her medical history included multiple chronic comorbidities. A contrast-enhanced thoracoabdominal computed tomography scan performed during her diagnostic workup revealed an interruption of the IVC at the infrarenal segment, with venous drainage diverted through a markedly dilated azygos vein. Additional findings included polysplenia and necrotic retroperitoneal lymphadenopathy, unrelated to the vascular anomaly. The interrupted IVC represented an incidental, asymptomatic finding. The patient's clinical management focused on evaluation of the lymphadenopathy and her comorbidities, with no intervention required for the vascular variant. Interruption of the IVC with azygos continuation occurs in less than 0.3% of the population and may be misinterpreted as lymphadenopathy or mediastinal masses. This variant has implications for procedures including transfemoral cardiac catheterization, IVC filter placement, venography, and cardiopulmonary bypass, as femoral access may be ineffective. Awareness of this anomaly also helps differentiate it from acquired causes of azygos dilation due to venous obstruction. Although rare, congenital interruption of the IVC with azygos continuation is clinically significant. Accurate identification is essential to avoid misdiagnosis and to ensure safe planning for interventions requiring venous access.