CTICasesLeft Isomerism (Polysplenia Syndrome) with Azygos Continuation of an Interrupted IVC
Imaging findings
A subtly widened mediastinal contour was traced to a markedly dilated azygos vein extending from the abdomen (draining an interrupted inferior vena cava) up into the chest, with hepatic veins forming a short conduit directly into the right atrium, consistent with azygos continuation of an interrupted IVC. Associated findings included an aberrant right subclavian artery, abnormal splenic position with no discrete spleen identified in its expected location, a transverse/symmetric distribution of the liver, and symmetric "left-type" bilateral bronchial and pulmonary arterial branching (long unbranched bronchi with pulmonary arteries anterior to rather than over the bronchi, and only a single fissure on the right).
Key takeaways
The combination of azygos continuation of an interrupted IVC, abnormal transverse liver, absent or malpositioned spleen, and bilateral left-sided bronchopulmonary branching is characteristic of left isomerism (polysplenia syndrome). Recognizing symmetric "left lung" bronchial branching bilaterally and loss of the normal right-lung fissure pattern helps confirm isomerism once a widened mediastinum prompts a search for an underlying systemic venous anomaly.
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