INTRODUCTION: Chylous pleural effusions usually result from obstruction of or injury to the thoracic duct. Surgery or trauma to the can lead to disruption of the thoracic duct or a tributary, resulting in leakage of chyle. Malignancies are the most common cause of nontraumatic chylothorax. Chylous effusions are almost always exudative, although transudates have rarely been reported.
CASE PRESENTATION: A 51-year-old female presented with symptoms of dyspnea, non-productive cough, pleuritic chest pain, and orthopnea. Her past medical history was significant for hypertension, type 2 diabetes, and hepatitis C. She had no history of surgeries. She quit smoking cigarettes four years previously, and had a 10-pack-year history. She admitted to occasionally smoking marijuana, and smoked crack cocaine 7 years previously. Her family history was significant for coronary artery disease in her father. Her medications included metformin, lisinopril, and furosemide. On exam, her blood pressure was elevated at 248/136 mmHg, and her heart rate was 102. Her other vital signs were within normal limits. Her breathing was mildly labored and she had absent breath sounds in her right chest. She had bilateral lower extremity pitting edema up to her knees. The remainder of her exam was normal. Laboratory workup was significant for BUN 25, creatinine 1.0, total protein 5.3, albumin 1.6, AST 46, and ALT 28. Her electrolytes and blood counts were normal. Urinalysis was significant for protein > 300. A chest radiograph revealed large right and small left pleural effusions. A CT scan of the chest confirmed these findings, with near complete atelectasis of the right lung and shift of the mediastinum to the left. CT of the abdomen showed moderate ascites and hepatomegaly. Thoracentesis was performed on the right chest with return of 1300 mL of milky fluid with the following characteristics: LDH 31, protein 1.0, triglycerides 185, cholesterol 9, WBC 25 (90% lymphocytes, 10% neutrophils), and RBC 195, consistent with a transudative chylothorax. Cytology and microbiologic studies did not show abnormalities. A repeat thoracentesis was performed three days later due to fluid re-accumulation, with similar findings. In evaluation of the chylothorax, ultrasound of the abdomen was performed, but there was not enough ascites present for paracentesis. Further work up revealed no evidence of cirrhosis, although a liver biopsy was not performed. An echocardiogram showed normal heart function with a small pericardial effusion. A 24 hour urine collection showed massive proteinuria, with greater than 11 g protein measured. A kidney biopsy was consistent with nodular glomerulosclerosis, likely from chronic uncontrolled diabetes. She was discharged home with the diagnosis of chylothorax related to nephrotic syndrome. She was started on insulin and was discharged on lisinopril, spironolactone, carvedilol, furosemide, and simvastatin. Since that time she has required one admission for repeat thoracentesis, and her kidney disease has progressed to stage IV.
DISCUSSION: Chylothorax is suspected when the pleural fluid triglyceride level is greater than 110 mg/dL and is confirmed with the detection of chylomicrons. Most chylous pleural effusions result either from obstruction or disruption of the thoracic duct. Common causes are surgical injury to the major lymphatic ducts and malignancy, and evaluation is normally directed towards these entities. These effusions are exudative by Light’s criteria. Approximately 20 cases of transudative chylothorax have been described, and most are associated with cirrhosis, nephrotic syndrome, or heart failure.1,2 The patient described above presented with transudative chylothorax due to severe nephrotic syndrome and chronic liver disease. The mechanism of chylous pleural effusion formation is thought to be translocation of chylous ascites across the diaphragm, although it is not clear how chylous ascites forms.3 The recognition of a transudative chylothorax is important because it narrows the search of an etiology to these specific entities and away from thoracic duct abnormalities.
CONCLUSIONS: Transudative chylothorax is a rare finding associated almost exclusively with nephrotic syndrome, cirrhosis, and heart failure.
Reference #1 Diaz-Guzman E, Culver DA, Stoller JK. Transudative chylothorax: report of two cases and review of the literature. Lung 2005; 183: 169-75.
Reference #2 Agrawal V, Doelken P, Sahn SA. Pleural fluid analysis in chylous pleural effusion. Chest 2008; 133:1436-41.
Reference #3 Romero S, Martin C, Hernandez L, et al. Chylothorax in cirrhosis of the liver: analysis of its frequency and clinical characteristics. Chest 1998; 114:154-9.
DISCLOSURE: The following authors have nothing to disclose: Timothy Saettele
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