Author: Amy Babb, MD - Yale University, School of Medicine - Yale New Haven Hospital
A 4-year-old undergoes an extracardiac Fontan procedure. On post-operative day 3, chest tube output increases and becomes milky after initiation of enteral feeds. Which mechanism MOST contributes to the increased risk of chylothorax in patients with Fontan physiology?
EXPLANATION
Chylothorax is the accumulation of lymphatic fluid (chyle) within the pleural space due to abnormal or disrupted flow within the thoracic lymphatic circulation.1,2 A recent study of almost 10,000 patients undergoing congenital cardiac operations, reported an overall post-operative chylothorax incidence of 3.2%.3 When analyzed by operation type, patients undergoing a Fontan procedure had the highest incidence of chylothorax at 20.5% - roughly 1 in 5 patients.3 Fontan patients who developed chylothorax also had higher post-operative central venous pressures and lower mean arterial pressures, supporting a link between hemodynamics and lymphatic dysfunction.3
The substantially higher incidence of chylothorax after Fontan surgery is increasingly thought to reflect the effects of Fontan physiology on lymphatic drainage rather than simply direct surgical injury of lymphatic structures.2-4 Total cavopulmonary connection results in elevated systemic venous pressures against which the lymphatic system must drain.1,2 Simultaneously, the higher venous pressures lead to increased capillary filtration and lymphatic production.1,2 The combination of increased lymphatic production and impaired drainage into the systemic venous system, results in lymphatic congestion, dilation, and abnormal lymphatic collateral formation and leakage.1,2 Advanced lymphatic imaging has demonstrated that direct traumatic thoracic duct injury accounts for only a minority of post-operative chylothorax cases, with abnormal lymphatic flow and dysfunction accounting for most.4
Chylothorax after Fontan procedure can lead to postoperative morbidity associated with the ongoing depletion of proteins, calories, lymphocytes, immunoglobulins and coagulation factors as well as pleural fluid accumulation that may impair respiratory function.5 A recent multicenter evaluation found Fontan patients with chylothorax required chest tubes longer (13 vs 7 days), had longer ICU admissions (7 vs 4 days), longer hospital stays (12 vs 9 days) and greater post-operative weight loss compared to those without chylothorax.5
Initial treatment focuses on nutritional modification and optimization of Fontan hemodynamics.1,2,6 A fat-modified diet restricts long-chain triglycerides while increasing medium chain triglycerides, which are preferentially absorbed in the portal circulation rather than the lymphatic system.1,2,6 Recent studies have shown that standardizing post-operative treatments beyond just diet modification, such as aggressive diuresis, fluid restriction and supplemental O2, further reduce the rate of chylothorax.6
Elevated pulmonary vascular resistance increases systemic venous pressure and therefore increases the risk of chylothorax. Decreased lymphatic production would reduce the risk of chylothorax and remains an important management goal after Fontan surgery. Elevated systemic venous pressure worsens lymphatic dysfunction and is the mechanism most strongly associated with the increased risk of chylothorax in Fontan physiology.
REFERENCES
1. Ahmed MA Sr. Post-Operative Chylothorax in Children Undergoing Congenital Heart Surgery. Cureus. 2021;13(3):e13811. Published 2021 Mar 10. doi:10.7759/cureus.13811
2. RochéRodríguez M, DiNardo JA. The Lymphatic System in the Fontan Patient-Pathophysiology, Imaging, and Interventions: What the Anesthesiologist Should Know. J Cardiothorac Vasc Anesth. 2022;36(8 Pt A):2669-2678. doi:10.1053/j.jvca.2021.07.049
3. Schaeffer T, Kunke V, Palm J, et al, Postoperative chylothorax following congenital heart surgery: incidence, risks, therapy, and possible mechanisms, JTCVS Open. 2026, doi: https://doi.org/10.1016/j.xjon.2026.102062
4. Savla JJ, Itkin M, Rossano JW, Dori Y. Post-Operative Chylothorax in Patients With Congenital Heart Disease. J Am Coll Cardiol. 2017;69(19):2410-2422. doi:10.1016/j.jacc.2017.03.021
5. Duran SR, Winder M, Reeder RW, et al. Pleural Drainage, Clinical Characteristics, and Management Strategies in the Perioperative Fontan Patient: A Multicenter Report. Pediatr Cardiol. 2026;47(1):171-179. doi:10.1007/s00246-024-03744-x
6. Ash A, Ryerson L, Anand V, et al. Use of a Postoperative Care Management Pathway Reduces the Incidence of Chylothorax Post-Fontan Palliation. Pediatr Cardiol. 2025;46(3):727-735. doi:10.1007/s00246-024-03494-w