Superior Vena Cava Thrombosis Presenting As Massive Chylothorax: A Report of a Rare Case.

Chylothorax is an uncommon condition resulting from the disruption or obstruction of the thoracic duct or its tributaries, leading to the accumulation of chyle in the pleural cavity. It can arise from both traumatic and non-traumatic causes. Non-traumatic etiologies include malignancies involving the mediastinum, followed by infections such as tuberculosis, connective tissue disorders (e.g., sarcoidosis, systemic lupus erythematosus), and, less frequently, radiation exposure and certain drugs. Although thoracic central venous thrombosis (CVT) is a recognized etiology, it remains a rare cause of chylothorax in adults. We report a rare case of massive chylothorax secondary to chronic CVT associated with a long-term indwelling central venous catheter in a patient undergoing hemodialysis for end-stage renal disease. The diagnosis of chylothorax was confirmed through pleural fluid analysis, which revealed characteristic findings, while the underlying cause was identified using targeted imaging modalities. This case highlights chylothorax's diagnostic complexity and clinical challenges in central venous obstruction. It also emphasizes the importance of maintaining a high index of suspicion in patients with relevant risk factors. A brief review of the underlying pathophysiology and available treatment approaches is also provided to aid clinicians in managing similar presentations.