Situs Ambiguous With Polysplenia With Azygos Continuation of the Inferior Vena Cava (IVC): A Case Report.

Situs ambiguous with polysplenia with azygos continuation of the inferior vena cava (IVC) represents an exceptionally rare spectrum of congenital anomalies resulting from the disrupted left-right access development during embryogenesis. Although most reported cases are identified in childhood due to the associated cardiac and biliary malformations, survival into adulthood without major comorbidities is uncommon and rarely documented. We presented the case of a 37-year-old female who presented to the emergency department with left leg swelling and persistent nausea and vomiting. Imaging performed for unrelated symptoms revealed multiple right-sided spleens, a predominantly left-sided liver, and an infrahepatic IVC draining via the azygos system into the superior vena cava (SVC), all of which are findings consistent with sinus ambiguous with polysplenia. This case is unique in demonstrating the incidental asymptomatic presentation of this complex anomaly in an adult without significant cardiobiliary comorbidities. From a radiological standpoint, awareness of this pattern is critical to prevent misinterpretations as simply a vascular obstruction or post-operative change. Clinically, the recognition of this anomaly is essential for surgical planning, central venous access, and interpretation of cross-sectional imaging. Reporting exceptionally rare adult cases like this patient aids in expanding the understanding of this heterotaxy's variable spectrum and emphasizes the importance of accurate radiological identification in optimizing patient care.