What is a thoracic duct lymphocele?

Thoracic Duct Lymphocele: Diagnosis and Management

A thoracic duct lymphocele is a rare pathological entity characterized by cystic dilation of the thoracic duct wall, resulting in a contained collection of lymphatic fluid that may be congenital or acquired following trauma or degeneration of the thoracic duct.

Definition and Pathophysiology

• A thoracic duct lymphocele refers to a cystic collection of lymphatic fluid resulting from deterioration and dilation of the thoracic duct wall 1
• It can occur as a primary (congenital or idiopathic) condition or secondary to trauma, surgery, or degenerative processes 1, 2
• Lymphoceles must be differentiated from other cystic lesions as failure to recognize their attachment to the thoracic duct may result in complications such as chylothorax 2

Anatomical Considerations

• The thoracic duct is the body's largest lymphatic conduit, draining approximately 75% of lymphatic fluid from the cisterna chyli to the left jugulovenous angle 3
• While a typical course has been described, it is present in only 40-60% of patients, with significant anatomical variations that can complicate diagnosis and treatment 3
• The thoracic duct's lengthy course predisposes it to injury from various iatrogenic disruptions, spontaneous benign and malignant lymphatic obstructions, and idiopathic causes 3

Clinical Presentation

• Thoracic duct lymphoceles may be asymptomatic or present with symptoms related to compression of adjacent structures 2
• When symptomatic, patients may experience chest pain, dyspnea, or symptoms related to the specific location of the lymphocele 1
• Mediastinal lymphoceles can mimic other thoracic injuries or conditions, including aortic rupture, paraspinal hematoma, esophageal injury, or mediastinal tumors 4

Diagnostic Approach

• Diagnosis is established through fluid analysis with diagnostic criteria including:

  • Pleural fluid triglyceride level >110 mg/dL
  • Ratio of pleural fluid to serum triglyceride level >1.0 5
  • Alkaline reaction, specific gravity between 1010 and 1021
  • Positive Sudan III stain for fat
  • High concentrations of triglycerides (5-50 g/l) and protein (22-60 g/l) 6

• Imaging modalities for diagnosis include:

  • Lymphangiography - gold standard for visualization of lymph nodes, lymphatic vessels, cisterna chyli, and thoracic duct 6, 7
  • CT imaging with 1 mm collimation and multiplanar reformation - can identify the thoracic duct and cisterna chyli in nearly 100% of cases with normal anatomy 6, 5
  • MRI - more reliably visualizes segments of the thoracic duct than CT alone 6, 7
  • Enhanced CT combined with lymphography can identify the location of the thoracic duct and its lymphatic connection to the pericardium 6

Management Options

Conservative Management

• Initial drainage of lymphocele provides both diagnostic confirmation and symptom relief 5
• Dietary modifications including a diet low in long-chain triglycerides (<5% of total energy intake) and enriched with medium-chain triglycerides 5
• Adjunctive pharmacological therapy may include somatostatin and etilefrine to reduce lymphatic flow 5
• Conservative management success rates approach 50% in nonmalignant etiologies 5

Indications for Invasive Treatment

• Failure of conservative management after 2 weeks 5
• High output (>500-1000 mL/day) of lymphatic fluid 5
• Persistent lymphocele despite conservative measures 5

Invasive Treatment Options

• Thoracic duct embolization (TDE) is the first-line invasive treatment for persistent thoracic duct lymphoceles, with technical success rates of 85-88.5% and clinical success rates of up to 97% for nontraumatic cases 5, 8
• Surgical options when TDE fails or is not available:
  • Complete surgical resection of the lymphocele 1
  • Thoracic duct ligation 5
  • Pericardio-peritoneal window for chylopericardium 6
  • Laparoscopic drainage with ablation of the lining for large lymphoceles 9

Complications and Prognosis

• Complications of untreated thoracic duct lymphoceles include:

  • Compression of adjacent structures
  • Risk of chylothorax if the lymphocele ruptures 2
  • Nutritional depletion and immunocompromised state due to loss of lymphatic fluid 3

• Complications of treatment:

  • TDE complications are generally minor (2-6%) and self-limited 5
  • Higher postoperative mortality rates (4.5-50%) have been reported with surgical thoracic duct ligation compared to TDE 5

Monitoring and Follow-up

• Regular monitoring of lymphatic fluid output to guide treatment decisions 5
• Assessment of nutritional status, especially protein levels 5
• Replacement of fluid and protein losses to maintain nutritional status 5

Special Considerations

• In cases of failed thoracic duct ligation, reassessment with combined CT and unilateral pedal lymphangiography can identify the cause and locate the leak in 75% of idiopathic cases 6
• Chylothorax occurs in about 2-3% of transthoracic esophagectomies, with high mortality if conservative treatment becomes prolonged 5