Nationwide Epidemiology, Etiology, and Management of Chylothorax: Analysis of 14,631 Hospitalized Patients from 2015–2024: An Epic Cosmos Study

Purpose: To delineate the demographic distribution, etiologic spectrum, and management patterns of patients hospitalized with chylothorax in the United States using the Epic Cosmos multi-institutional database.

Materials and Methods: We performed a retrospective cohort study of 14,631 patients hospitalized with chylothorax between 2015–2024 using Epic Cosmos, a federated electronic health record dataset encompassing >200 million patient records across 180+ U.S. institutions. Extracted variables included demographics, comorbidities, etiologies, and management strategies. Demographics encompassed age, sex, race/ethnicity, insurance status, BMI, census region, and area deprivation index. Etiologies were classified as iatrogenic, traumatic, malignant, or medical. Therapies, including conservative management and interventional approaches, were analyzed. Hematologic parameters were assessed pre- and post-embolization.

Results: Age distribution was < 18 years (39.8%), 18–44 (9.2%), 45–64 (21.3%), 65–74 (17.9%), 75–84 (10.2%), and ≥85 (2.7%); 54.6% were male. The South accounted for the largest regional cohort (43.5%). Race/ethnicity was predominantly White (77.0%), followed by Black (14.4%) and Hispanic (13.5%). Leading etiologies included iatrogenic (congenital heart surgery, n=1,515; pulmonary resection, n=470), traumatic thoracic/neck injury (n=740), malignancy (lung cancer, n=1,120; metastatic disease, n=1,464; lymphoma, n=1,021), and medical conditions (heart failure, n=4,039; cirrhosis, n=744; congenital lymphatic abnormality, n=500). Initial or concurrent conservative therapy was employed in 42.7% (n=6,246). Among those requiring escalation, chest tube drainage was instituted in 0–3 days in 519 patients (8.3% of the conservatively managed group), 4–7 days in 295 (4.7%), and 8–14 days in 267 (4.3%). Among patients with laboratory data, pre-embolization lymphopenia ( < 25% lymphocytes) was present in 74.7%, with persistence at ≥5 days post-embolization in 85.5%.

Conclusion: Leveraging the Epic Cosmos national dataset, this study provides the largest epidemiologic analysis of hospitalized chylothorax to date. Heart failure, thoracic malignancy, and congenital heart surgery were the most prevalent causes. Nearly half of patients underwent conservative management, yet over 17% required chest tube placement within 14 days, most commonly within the first 3 days. These findings underscore the substantial clinical burden of chylothorax and highlight opportunities to refine timing and selection of interventional strategies.