Chylopericardium

Chylopericardium is accumulation of chyle, lymph rich in chylomicrons and triglycerides, in the pericardial sac. The fluid is milky and opalescent. It is rare and results from disruption or obstruction of the thoracic duct or its tributaries, with retrograde flow into pericardial lymphatics.

Causes are post-surgical or traumatic thoracic duct injury (cardiac, oesophageal and mediastinal surgery, central line placement), lymphoma and other mediastinal tumours, mediastinal tuberculosis, thrombosis of the superior vena cava or subclavian vein, radiotherapy, lymphatic malformations (lymphangiomatosis, Gorham-Stout disease, Noonan syndrome, yellow nail syndrome), filariasis, sarcoidosis and congenital communications. A large fraction remain idiopathic.

It often coexists with chylothorax. Tamponade is uncommon because accumulation is slow. Constrictive pericarditis, malnutrition, lymphopenia and hypoalbuminaemia are the main late complications.

Pathophysiology.

The thoracic duct carries 1.5 to 2.5 litres of lymph each day, mostly chylomicron rich chyle from the gut, to the junction of the left subclavian and internal jugular veins.

Venous hypertension, duct obstruction, injury or incompetent valves allow chyle to flow retrograde through mediastinal lymphatics into the pericardium. Chyle irritates the pericardium and drives fibrosis.

Chronic loss of chyle removes lymphocytes, immunoglobulins, albumin, fat soluble vitamins and essential fatty acids, leading to lymphopenia, infection risk and malnutrition.

Progressive dyspnoea, chest discomfort, fatigue, cough, weight loss and peripheral oedema. Tamponade or constriction signs appear in a minority. Look for features of the cause: lymphadenopathy, lymphoedema, yellow nails, recent surgery or trauma, central venous catheters and a history of residence in filarial endemic areas. Pleural effusion is common, with milky fluid.

• Echocardiography for effusion size, tamponade and constriction.
• Fluid analysis: milky, opalescent fluid that does not clear with alkali, triglyceride over 1.24 mmol/L (110 mg/dL) and higher than plasma, cholesterol to triglyceride ratio under 1, chylomicrons on lipoprotein electrophoresis, lymphocyte predominance, and positive Sudan III staining. A triglyceride under 0.56 mmol/L (50 mg/dL) makes chyle unlikely. Send culture, mycobacterial tests and cytology.
• CT of chest, abdomen and pelvis for nodes, mass, thrombosis and duct anatomy. MR lymphangiography or intranodal lipiodol lymphangiography locates the leak and guides intervention. Lymphoscintigraphy where available.
• Full blood count and differential (lymphocyte count), albumin, immunoglobulins, lipid profile, vitamins A, D, E and K status, HIV test, tuberculosis tests, filarial antigen or blood film where relevant, and biopsy of any node or mass.

Differential diagnosis.

• Pseudochylopericardium (cholesterol rich effusion with crystals and low triglyceride, from long standing hypothyroid, tuberculous or rheumatoid effusion).
• Purulent, haemorrhagic and malignant effusion.
• Chylothorax with secondary pericardial involvement.
• Lipid rich effusion from hypothyroidism or nephrotic syndrome.

Treat the cause.

• Lymphoma: systemic chemotherapy, with or without radiotherapy, by histology.
• Tuberculosis: isoniazid 5 mg/kg (maximum 300 mg), rifampicin 10 mg/kg (maximum 600 mg), pyrazinamide 25 mg/kg (maximum 2 g) and ethambutol 15 mg/kg (maximum 1.2 g) once daily for 2 months, then isoniazid and rifampicin for 4 months, with pyridoxine 25 mg daily and liver tests at baseline, 2 weeks and monthly.
• Filariasis: diethylcarbamazine 6 mg/kg orally daily for 12 days, with specialist advice.
• Venous thrombosis: anticoagulation and removal of the catheter. Radiation and surgical causes: conservative treatment first.

Drainage. Pericardiocentesis under echocardiographic control with a pigtail catheter for tamponade or large symptomatic effusion. Recurrence after drainage alone is common.

Conservative treatment (post-surgical and traumatic leaks, first 2 to 4 weeks).

• Diet: long chain fat under 10 g daily with medium chain triglyceride formula or oil as the main fat source (absorbed through the portal vein, not the lymphatics), high protein (1.5 g/kg daily), and supplements of vitamins A, D, E and K and of essential fatty acids, under dietitian supervision.
• Complete bowel rest with parenteral nutrition (including intravenous lipid emulsion) when output is high or diet fails within 1 to 2 weeks.
• Octreotide 100 microgram subcutaneously every 8 hours (range 50 to 200 microgram), assessed after 3 to 5 days and continued for 1 to 2 weeks if output falls; in children 0.5 to 1 microgram/kg/h by infusion. Monitor glucose, heart rate, gallbladder symptoms and thyroid function.
• Sirolimus 0.8 mg/m2 orally twice daily, adjusted to a trough of 5 to 15 ng/mL, for lymphatic malformations or refractory leaks (limited evidence); monitor lipids, infection, proteinuria, wound healing and CYP3A4 interactions.

Interventional and surgical treatment (output over 500 to 1000 mL daily, failure after 2 to 4 weeks, or complications):

• Percutaneous thoracic duct embolisation with coils or glue after lymphangiography, often the first choice.
• Thoracic duct ligation (thoracoscopic or open), with a high fat load (for example 100 mL of cream or olive oil) 2 to 3 hours before surgery to show the leak. Combine with pericardial window.
• Pericardial window or pericardio peritoneal shunt for recurrent effusion.
• Pericardiectomy for constriction.

Monitoring. Drain output and fluid triglyceride daily, weight, albumin, lymphocyte count and immunoglobulins weekly, vitamin levels every 3 months, echocardiography at 1 to 2 weeks, 1 month and 3 months.

Referral and escalation. Refer to cardiology and thoracic surgery or interventional radiology with lymphatic expertise. Urgent referral for tamponade, high drain output, infection, severe malnutrition or constriction.

Special groups.

• Pregnancy: drain for tamponade; avoid sirolimus and filarial drugs unless essential.
• Children: octreotide 0.5 to 1 microgram/kg/h by infusion; medium chain triglyceride formula; growth monitoring; early lymphatic imaging.
• Kidney or liver impairment: give pyrazinamide and ethambutol three times weekly when creatinine clearance is under 30 mL/min, stop hepatotoxic antituberculosis drugs if ALT exceeds 3 times the upper limit of normal with symptoms or 5 times without, and monitor glucose on octreotide.
• Region specific: filariasis and tuberculosis are important causes and should be tested for in endemic areas.