Extensive Deep Vein Thrombosis With Intraabdominal Extension Triggered by Oral Contraceptive Use in a Young Patient With Interrupted Inferior Vena Cava With Azygos Continuation: A Case Report.

Congenital malformations of the inferior vena cava (IVC) are rare and often asymptomatic, typically discovered incidentally during imaging. However, these anomalies can result in circulatory stasis, impede venous return, and serve as predisposing factors for thrombus formation. Here, we present a unique case of a 28-year-old female patient who was found to have interrupted IVC with azygos continuation, an exceedingly rare IVC anomaly, during a work-up of extensive bilateral deep vein thrombosis (DVT) with an intraabdominal extension which was triggered by recent combined oral contraceptive pills (OCP) use. This case highlights the importance of considering vena cava malformations as an underlying cause for extensive DVT, even in the absence of conventional risk factors. Clinicians should be aware of the potential association between congenital vena cava anomalies and thrombotic events, as early recognition and appropriate management are crucial for preventing complications such as pulmonary embolism.