Epidemiology
- Definition: chylothorax is the presence of chylus (lymph) in the pleural space due to damage to the thoracic duct
Etiology
Neoplasm
- General Comments: neoplasms account for >50% of cases
- Lymphoma (see Lymphoma, [[Lymphoma]]): most common non-traumatic etiology (represents 75% of malignancy-associated cases)
- Likely results from lymphoma cells invading the wall of the thoracic duct
- Lymphoma cells are typically not seen in pleural biopsies or biopsies of the thoracic duct
- Lung Cancer (see Lung Cancer, [[Lung Cancer]])
- Kaposi Sarcoma (see Kaposi Sarcoma, [[Kaposi Sarcoma]])
- Other Malignancies
- Benign Tumors
Traumatic Chylothorax
General Comments
- Trauma is 2nd Most Common Etiology of Chylothorax
Surgery/Procedures
- General Comments: especially common with intrathoracic procedures which involve the left subclavian artery
- Cardiothoracic Surgery (0.5% incidence): including thoracoscopy
- Central Venous Catheter (CVC) (see Central Venous Catheter, [[Central Venous Catheter]])
- Cervical Node Dissection
- Esophageal Resection (2% incidence): especially transhiatal approach
- Esophagogastroduodenoscopy (EGD) with Variceal Sclerotherapy (see Esophagogastroduodenoscopy, [[Esophagogastroduodenoscopy]])
- High Translumbar Aortogram
- Peritoneovenous Shunt (LeVeen Shunt) with Superior Vena Cava Obstruction (see Peritoneovenous Shunt, [[Peritoneovenous Shunt]])
- Pneumonectomy
- Sellate Ganglion Blockade
- Subclavian Vein Central Venous Catheter in the Presence of Thrombosis (see Central Venous Catheter, [[Central Venous Catheter]])
- Thoracic Sympathectomy
Trauma
- General Comments: closed-traumatic disruptions usually occur on right side near T9-T10
- Childbirth
- Coughing
- Head and Neck Surgery
- Hiccuping
- Hyperextension of Spine
- Penetrating Injury of Neck or Thorax
- Straining
- Stretching While Yawning
- Vertebral Fracture: especially after fatty meal
- Vomiting (see Nausea and Vomiting, [[Nausea and Vomiting]])
- Weight Lifting
Neonatal Chylothorax
- Most common cause of pleural effusion in first few days of life
- Usually right-sided or bilateral
- Possibly due to increased fetal venous pressure during delivery
- Increased incidence with hydramnios
Idiopathic Chylothorax
- General Comments: accounts for 15% of cases
Other
- Amyloidosis (see Amyloidosis, [[Amyloidosis]])
- Behcet’s Disease (see Behcet’s Disease, [[Behcets Disease]])
- Congenital Chylothorax: due to congenital malformation of thoracic duct (although can also be observed after traumatic childbirth)
- Congestive Heart Failure (CHF) (see Congestive Heart Failure, [[Congestive Heart Failure]]): with increased central venous pressure
- Fibrosing Mediastinitis (see Granulomatous Mediastinitis and Fibrosing Mediastinitis, [[Granulomatous Mediastinitis and Fibrosing Mediastinitis]])
- Filiariasis
- Hemangiomatosis (Gorham’s Syndrome)
- Intestinal Lymphangiectasia (Noonan’s Syndrome)
- Lymphangioleiomyomatosis (see Lymphangioleiomyomatosis, [[Lymphangioleiomyomatosis]]): occurs in 28% of cases
- Mediastinal Lymphadenopathy (see Mediastinal Mass, [[Mediastinal Mass]])
- Other Central Vein Thrombosis
- Radiation Therapy (see Radiation Therapy, [[Radiation Therapy]]): often late sequela
- Retrosternal Goiter
- Sarcoidosis (see Sarcoidosis, [[Sarcoidosis]])e
- Superior Vena Cava (SVC) Syndrome (see Superior Vena Cava Syndrome, [[Superior Vena Cava Syndrome]])
- Thoracic Aortic Aneurysm (see Thoracic Aortic Aneurysm, [[Thoracic Aortic Aneurysm]]): due to erosion of thoracic duct
- Thoracic Duct Lymphangitis
- Transdiaphragmatic Movement of Chylous Ascites
- Tuberculosis (see Tuberculosis, [[Tuberculosis]]): with mediastial involvement
- Tuberous Sclerosis (see Tuberous Sclerosis, [[Tuberous Sclerosis]])
- Yellow Nail Syndrome (see Yellow Nail Syndrome, [[Yellow Nail Syndrome]])
Physiology
- Anatomy (note that anatomy is variable with anomalous course in 60% of humans): lymph vessels from lower extremities and peritoneal cavity join together behind the aorta and inferior to the diaphragm to form the cisterna chyli, the origina of the thoracic duct -> thoracic duct passes through diaphragm and runs along the right paravertebral space (between the azygos vein and the aorta
- At the 3rd-4th vertebra, thoracic duct crosses into the left thorax
- Thoracic duct then turns laterally and makes a small loop in the neck region
- Thoracic duct usually empties into the left subclavian vein, between jugular and vertebral veins (however, anatomic variably occurs and it can empty into the right subclavian vein)
- Thoracic duct has valves (with thoracic motion causing forward movement of the chyle) -> allows chyle to only move forward through the duct
- There are numerous small connections of thoracic duct with veins -> this allows duct to be ligated safely
- Chyle contains triglycerides, chylomicrons, protein, and lymphocytes (originating from the GI tract) -> chyle is bacteriostatic
- Normal chyle flow is 2L per day
- Chyle production increases with PO intake
- Chyle contains chylomicrons, composed of long-chain triglycerides
- Chylothorax results from obstruction or disruption of the thoracic duct
- Chylothorax is usually right-sided: since most of the duct is within the right hemithorax
- If thoracic duct injury occurs at the level of the aorta -> left chylothorax can occur
- If thoracic duct injury occurs at point of crossover in the thorax -> bil chylothorax can occur
- Note: ligation of thoracic duct does not produce chylothorax (due to collaterals and lymphatico-venous anastomoses)
Diagnosis
- CXR/Chest CT
- Pleural effusion (usually right-sided)
- Chest/Abd/Pelvic CT is necessary to exclude intrathoracic tumor (particularly lymphoma)
CXR/Chest CT patterns: chyloma may occur in posterior mediastinum before chylothorax develops (disappears when mediastinal pleura ruptures into pleural space)
-Pleura is normal (chyle is non-irritating)
- Lymphangiogram
- Useful in some cases to demonstrate if disease is localized of diffuse
- May demonstrate leak or level of obstruction
- Pleural Fluid:
- Appearance: ususlly appears thick, opalescent, whitish or coffee-colored, due to high fat content (however, only 47% of cases demonstrate the characteristic odorless, milky, turbid fluid of chylothorax)
- Neonatal chylothorax is serous until milk is fed
- Triglyceride: elevated
- Trig >100 mg/dL: diagnoses chylothorax (chylothorax fluid clears with addition of ethyl ether)
- Trig <50 mg/dL: rules out chylothorax
- Trig 50-110 mg/dL: perform lipoprotein analysis for chylomicrons to diagnose chylothorax
- Chylomicron: positive
- Centrfugation: will not clear fluid in chylothorax (as opposed to in empyema, where centrifugation will sediment the cells result in a clear supernatant)
- LDH:
- Total Protein: usually >30 g/L
- Electrolytes: same as serum
- Cells: mostly T-cells
- Ethyl Ether: causes clearing of fluid
- Appearance: ususlly appears thick, opalescent, whitish or coffee-colored, due to high fat content (however, only 47% of cases demonstrate the characteristic odorless, milky, turbid fluid of chylothorax)
Clinical Manifestations
Chyloma
- Epidemiology: this presentation is more common after traumatic thoracic duct injury
- Physiology: local chyle collection that forms acutely in the chest
- Chyle subsequently migrates into mediastinum (chylomediastinum), pericarium (chylopericardium), or into the pleural space (chylothorax)
- Clinical
- Acute Chest Pain (see Chest Pain, [[Chest Pain]])
- Dyspnea (see Dyspnea, [[Dyspnea]])
- Swelling in Supraclavicular Fossa: occasional
- Tachycardia (see Sinus Tachycardia, [[Sinus Tachycardia]])
Pleural Effusion
- Epidemiology: typical presentation
- Clinical
- Onset
- Non-Traumatic Cases: gradual onset
- Traumatic Cases: subacute onset
- May be acute with associated hypotension in some cases
- Rate of Chyle Accumulation: rate of accumulation depends on diet
- High Fat Meal: increases chyle flow 2-10x normal for several hrs
- Ingestion of Liquid (But not Carbohydrate or Protein): increases chyle flow
- Absence of Chest Pain and Fever: chyle is non-irritating and bacteriostatic
- Atelectasis (see Atelectasis, [[Atelectasis]]): may be present
- Increased Risk of Infection: due to loss of lypmhocytes in chyle
- Nutritional Depletion: due to loss of protein, water, electrolytes, fats) -> exacerbated by thoracenteses, chest tube
- Onset
- Treatment
- Accumulation After Thoracentesis: rapidly reaccumulates
Treatment
Dietary Modification with Observation
- Low-Fat Diet (with medium-chain triglycerides, which are predominantly absorbed drectly in to the blood): may decrease chyle flow
- TPN: may decrease chyle flow
- In traumatic cases, approximately 50% of chylothoraces will heal with conservative management
Chemical Pleurodesis
- Pleurodesis (with tetracycline, bleo, talc): may be necessary, especially for malignancy-associated cases
- It is generally believed that pleurodesis success rates are lower in chylothorax than for other malignant effusions
Pleuroperitoneal Shunt
- May be considered early to avoid malnutrition (especially in idiopathic cases)
- Contraindication: co-existent chylous ascites
- Requires daily pumping by the patient
- May require replacement, in cases where shunt fails to function
Thoracoscopic Ligation of the Thoracic Duct
- Ligation of duct just above the diaphragm
- Usually successful and well-tolerated (due to collaterals from thoracic duct into other veins)
Mediastinal XRT
- Usually effective (in 68% of lymphoma cases and 50% of metastatic cancer cases)
References
- Eur Resp J 1997 ; vol. 10 no. 5 1157-1162
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