Treatment Outcomes and Temporal Changes in Pleural Fluid Characteristics in Persistent Postoperative Chylothorax Following Congenital Heart Surgery.

Postoperative chylothorax remains a significant complication after congenital heart surgery; however, little is known about temporal changes in pleural fluid characteristics during prolonged disease. We retrospectively reviewed 82 children with postoperative chylothorax treated between 2007 and 2023 to evaluate the outcomes of a stepwise treatment strategy, identify factors associated with refractory disease, and investigate serial pleural fluid findings. Patients were managed with dietary modification, total parenteral nutrition, octreotide, and additional intervention when necessary. Conservative management successfully resolved chylothorax in 70 patients (85.4%), whereas 12 (14.6%) required additional intervention. Multivariable Firth penalized logistic regression identified greater pleural drainage volume (adjusted OR, 1.83 per 10 mL/kg/day increase; P = 0.025) and superior vena cava stenosis or obstruction (adjusted OR, 75.94; P < 0.001) as independent predictors of additional intervention or death. Serial pleural fluid analyses demonstrated progressive declines in white blood cell counts despite persistent mononuclear cell predominance, while triglyceride concentrations remained below the conventional diagnostic threshold throughout prolonged chylothorax. These findings suggest that conventional pleural fluid criteria alone may underestimate persistent postoperative chylothorax during long-term follow-up. Assessment of refractory chylothorax should therefore integrate the clinical course, hemodynamic findings, and imaging studies in addition to pleural fluid analysis.