Chylomediastinum after cardiac surgery through median sternotomy: A case report

Introduction

Idiopathic chylopericardium is characterized by chylous leakage and represents a rare complication of cardiac surgery via a median sternotomy. ¹ A few cases of chylomediastinum or chylopericardium have been reported. We herein report a case of chylomediastinum after aortic valve replacement through a conventional median sternotomy.

Case

A 79-year-old woman underwent aortic valve replacement through a standard full sternotomy. During the procedure, the anterior mid-portion of the left parietal pleura was injured. The thymus exhibited fatty degeneration and was divided with ligation at the mid-portion of the body without separation between the right and left lobes. The superior and inferior vena cavae were snared. The operation was successfully completed under ordinary cardiopulmonary bypass and cardiac arrest. Drainage tubes were placed in the retrosternal space and left thoracic cavity.

On the operative day, 300 mL of bloody fluid from both drainage tubes was discharged. On the first postoperative day, the patient began oral intake. On the second postoperative day, 100 mL of milky fluid was observed from the drainage tube of the retrosternal space, and the fluid from the thoracic cavity remained slightly bloody (Figure 1). We diagnosed the patient with chylomediastinum based on the characteristic appearance of the fluid and the relationship between oral intake and the event. The drainage and low-fat total parenteral nutrition were continued for 1 week, leading to complete disappearance of the chylous discharge. The drainage tubes were removed upon the disappearance of chylous discharge after standard oral intake. The patient was doing well without fluid collection in the mediastinal and pericardial cavities 2 months after the operation.

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Figure 1.

Discharge of fluid from the retrosternal space.

Discussion

Chylous discharge might occur after abdominal or thoracic surgery. Intraoperative injuries to the thoracic duct and/or its tributaries cause this rare complication. However, chylous discharge after cardiac surgery through a median sternotomy has also been reported. This complication is rare and mainly occurs in infants with congenital heart disease. The thymus gland is active in young patients but atrophic in adults. ² Chylous discharge is extremely rare in adults. Chylous collection might lead to infective complications such as mediastinitis; ³ thus, prompt and adequate treatment is essential.

In our case, a drain was not placed in the pericardial cavity, and we were therefore unable to determine whether the chylous liquid arose from the mediastinum. We inferred that the chylous discharge came from around the thymus because the thymus was divided at the mid-portion of the body without separation between the right and left lobes. The drainage volume was <100 mL/day and the conservative treatment with total parenteral nutrition ⁴ was effective.

Oz et al. ⁵ indicated that lymphatic channels are present around the inferior vena cava and the thymus. Snaring of the vessel and division of the thymus might cause postoperative chylous discharge. Gentle and limited exploration is required to prevent such a complication. We recommend division of the thymus between right and left lobes with minimal sharp dissection.

In conclusion, we described a 79-year-old woman who developed chylomediastinum after aortic valve replacement. The patient fully recovered after 1 week of total parenteral nutrition. We conclude that gentle and minimally invasive exploration is required during venous snaring and thymus division for cardiac surgery.