Pediatric chylothorax—lymphatic imaging enables targeted surgical treatment

Abstract

Chylothorax—the collection of lymphatic fluid in the pleural space—is a rare finding in otherwise healthy adolescents. Initially, clinical signs and symptoms are often non-specific and a wide range of underlying causes necessitates extensive diagnostic workup. Treatment options include dietary measures, medical treatment, and various surgical procedures. We report about a 12-year-old boy with accidental diagnosis of chylothorax. Lymphatic imaging led to visualization of a leakage of an accessory left-sided thoracic duct and thoracoscopic clipping was successfully performed. Lymphatic imaging procedures depict underlying causes of chylothorax allowing targeted therapeutic management.

Introduction

Chylothorax—an accumulation of lymphatic fluid (chyle) in the pleural cavity—is rare in childhood and adolescence. In contrast, in neonates, chylothorax is the most frequent cause of pleural effusion and a wide range of diseases and conditions may be the cause [1, 2].

Acute disruption of the thoracic duct may occur in cardio-thoracic surgery, blunt chest injury, or even severe coughing [1]. In contrast to this, chylothorax due to lymphatic anomalies may evolve slowly over a long period and therefore at first presents with discrete signs and symptoms [1]. Thoracic lymphatic anomalies include thoracic lymphangioma, congenital pulmonary lymphangiectasia or lymphangiomatosis-like Gorham-stout disease [3]. In our patient, an accessory thoracic duct feeding a microcystic lymphatic malformation has led to massive chylothorax. As seen in our case, there exist several anatomic variants of the thoracic duct including atresia of the thoracic duct that may lead to chylothorax.

Case report

A 12-year-old boy complained about recurring back pain for 1 year. He had no dyspnea but he mentioned to be quickly out of breath when playing football. He noticed no weight loss and no fatigue but recently a decreased exercise capacity. Since 2 weeks, he had a dry cough without fever.

Because of suspected scoliosis, an orthopedist initiated spinal x-ray. Unexpectedly, spinal radiography showed near total opacity of the left hemithorax (Fig. 1). Chest x-ray and thoracic ultrasound examination confirmed left-sided pleural effusion. Ultrasound examination of the abdomen and the lymphatic nodes of the cervical, axillary, infra- and supraclavicular, and inguinal region was normal. Transthoracic echocardiography confirmed patency of the superior caval vein and normal structure and function of the heart. Magnetic resonance imaging (MRI) of chest and abdomen performed to rule out a solid tumor showed space-occupying pleural effusion (Fig. 2) but no mass.

Fig. 1.

Long spine radiograph anterior-posterior projection: homogenous opacity of the left hemithorax up to the axilla, loss of diaphragmatic, and left cardiac silhouette

Fig. 2.

Thoracic MRI (cor stir): space-occupying left-sided pleural effusion

Diagnostic and therapeutic chest tube insertion revealed 1000 ml of milky, white fluid. Laboratory analysis of the pleural fluid showed triglyceride level of 1819 mg/dl and cholesterol level of 103 mg/dl; total cell count was 1200/μl—mainly lymphocytes. The bacteriological investigation of the fluid was negative. Meanwhile, the chest tube revealed more than 1000 ml chyle per 24 h despite of a medium-chain triglyceride diet.

To depict suspected thoracic duct injury, lymphatic imaging with magnetic resonance imaging was performed. In general anesthesia, gadolinium-based contrast agent was injected into groin lymph nodes. A 3 Tesla MRI equipment was used to subsequently examine the lymphatic anatomy ascending from the groin to the cervical level. MRI post-processing included maximum-intensity-projection (MIP) reconstruction. MR—lymphangiography showed a left-sided subpleural and intercostal lymphatic malformation between eight and eleventh thoracic vertebrae fed by an accessory chylous vessel ascending from the cisterna chyli (Fig. 3a, b). This accessory lymphatic vessel ascended to the left of the thoracic duct.

Fig. 3.

a, b MR lymphangiography (fl3d KM MIP): Injecting gadolinium-based contrast material into groin lymph nodes depicts an anomalous left-sided thoracic duct feeding a subpleural and intercostal lymphatic malformation

Identification of this anatomic variant of an accessory left-sided thoracic duct feeding a lymphatic malformation enabled us to perform thoracoscopic ligation of the accessory chylous vessel. Intraoperative depiction of the accessory thoracic duct with methylene blue lymphography failed: the lymphatic vessel of an inguinal lymphatic node was cannulated under ultrasound guidance by an experienced radiologist but no intrathoracic lymphatic vessel presented itself colored. During thoracoscopic preparation in the left periaortic angle, flow of chyle became suddenly visible. The now disrupted accessory thoracic duct was ligated with two titan clips and the chyle secretion stopped immediately. Accompanying subpleural lymphatic malformation was treated with local pleurectomy and electric cauterization. At the end of the procedure that lasted 60 min, a chest tube was inserted. Chest tube obtained serous fluid and was removed 5 days after surgery. The boy was dismissed home 6 days after surgery and chest x-ray showed no recurrence of chylothorax. Histological workup of the pleura-specimen revealed microcystic lymphatic malformation. At a follow up examination 6 months and 1 year after the surgery, the boy was free of clinical discomfort and showed a normal chest x-ray.

Discussion

Chylothorax due to iatrogenic injury to the thoracic duct may occur after various thoracic surgical procedures even subclavian vein cannulation. Non-iatrogenic injury to the thoracic duct occurs after blunt chest or abdominal trauma and has been linked to heavy child abuse [1]. In rare cases, severe vomiting or coughing may suffice to cause traumatic chylothorax [4].

In pediatric cardiac surgery, chylothorax is a significant postoperative problem with an incidence of about 2.8% [5]. Chylothorax after pediatric cardiac surgery may be the result of altered lymphatic circulation due to high venous pressure, e.g., in patients with Fontan-circulation or occlusion of the superior caval vein (e.g., thrombosis) [6].

Pulmonary or pleural lymphangiectasis, lymphangioma, and lymphangiomatosis occurring isolated or as a part of a syndrome cause chylothorax.

Accumulation of chyle in the pleural cavity typically leads to symptoms such as coughing, dyspnea, and chest pain. Nontraumatic chylothorax may be asymptomatic for a long period [1]. In these patients, immunodeficiency with recurrent infections or malnutrition may be the leading symptoms [1]. In our patient, back pain was the initial symptom of left-sided chylothorax. Retrospectively in this case, the duration of about 1 year and recurrence of back pain must have been regarded as red flags indicating a serious underlying pathology. It is noteworthy that despite the massive fluid collection in the left pleural cavity, significant pulmonary symptoms were missing.

Thoracocentesis leads to the correct diagnosis. Triglyceride levels > 110 mg/dl and chylomicrons can be found. Chylothorax is not a visual diagnosis: Milky and turbid fluids can be found in empyema or pseudochylothorax too and in neonates, chyle initially appears serous and becomes only milky with the onset of enteral feedings. When a chest tube is inserted, the amount of chylus from the drainage must be quantified. More than 10 ml/kg per day seem to carry the risk of problematic fluid and immunoglobuline losses [1].

Diagnostic workup initially aims at clarifying the underlying cause of chylothorax. Computed tomography (CT) and MRI may help to rule out solid tumors and to depict lymphatic malformation. Recently, lymphatic imaging by MR lymphangiography has brought increased understanding of lymphatic disorders [7]. There are no general guidelines for management of chylothorax in children. It is the aim of any therapeutic strategy to relieve symptoms, to prevent recurrence, and to treat the underlying disease. Surgical procedures try to close a thoracic duct leak by ligature or clipping of the duct. This procedure may be performed by video assisted thoracoscopy or open surgery with good results [8].

A median length of hospital stay of 29 days for children < 16 years who developed chylothorax as reported by Haines et al. reflects the impact of pediatric chylothorax on patient, family, and hospital resources necessitating optimal treatment [9].

MR lymphangiography can precisely depict the anatomy of a lymphatic malformation causing chylothorax and is therefore enabling targeted treatment— in our case leading to faster recovery and cure.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with animals performed by any of the authors.

Informed consent

Informed consent was obtained from all individual participants included in the study.