chylothorax

06/26/13 amr badreldin hamdy MD FCCP 1

ChylothoraxAmr Badreldin Hamdy

MD, FCCP


Definition

A chylothorax is formed when the thoracic duct is disrupted and chyle enters the pleural space.


Drainage from the thoracic duct is called chyle.

Ductal lymph is clear during fasting and becomes milky after a fatty meal.

Principal function of the thoracic duct is the transport of digestive fat to the venous system.


Chyle appears grossly as milky, opal- escent fluid that usually separates into three layers upon standing:

> a creamy uppermost layer containing chylomicrons,

> a milky intermediate layer,>a dependent layer containing

cellular elements.


The flow rate through the duct is affected by the rate of lymph formation in the gastrointestinal tract.


Anatomy


The thoracic duct (TD) is constant only in its variability.

It originates from the cisterna chyli which overlies the anterior surface of the second lumbar vertebra, posterior to and to the right of the aorta. It passes through the esophageal hiatus of the diaphragm into the thoracic cavity.


The TD ascends extrapleurally in the posterior mediastinum along the right side of the anterior surface of the vertebral column and lies between the azygos vein and the descending aorta in close proximity to the esophagus and pericardium.


At T5 - T7 it crosses to the left behind the aorta and ascends on the left side of the esophagus. Once the TD passes the thoracic inlet, it arches 3 to 5 cm above the clavicle and passes anterior to the sublcavian artery, vertebral artery and thyrocervical trunk to terminate in the region of the left jugular and subclavian veins.


A bicuspid valve prevents entry of blood into the lymphatic system.

The right duct is small ( 2cm in length) and drains lymph from right head and chest.


Unidirectional flow is ensured by:

- multiple valves throughout the duct,

- intrinsic wall contraction,- thoracic pressure gradient.


Daily between 1,500 and 2,500 mL of chyle normally empties into the venous system.

Ingestion of fat can increase the flow of lymph in the TD by 2-10 times the resting level for several hours.


Ingestion of liquid increases the chyle flow, whereas the ingestion of protein or carbohydrates has little effect on lymph flow.

The protein content is usually above 3g/dL, the electrolyte composition of chyle is similar to that of serum.


Composit ion of Chyle


LipidsFat is the main component of

chyle.Sixty to seventy percent of

ingested fat absorbed by intestinal lymphatics is conveyed to the blood by the thoracic duct.


Lymphatic fat is transported as chylo-microns.

Fatty acids with less than 10 carbon atoms are absorbed directly into the venous portal system.


Proteins Lymphatics are the main

pathway for return of extra-cellular proteins to the vascular space.

The protein content is half the concentration of plasma.


Electrolytes

Electrolyte composition is similar to plasma.


Cells Lymphocytes are the main cellular

elements. Ninety percent are T-lymphocytes. The primary cell in chyle is the

small lymphocyte (400 - 6,800/mm3).

Prolonged drainage of a chylous PE can result in profound T-lymphocyte depletion.


Pathophysiology of Chyle


@ it leads to cardiopulmonary abnormalities and metabolic immunologic deficiencies.

@ it can compress the lung resulting in dyspnea and respiratory distress.

@ empyema is a rare complication due to the bacteriostatic nature of lecithin and fatty acids.


@ loss of proteins and vitamins, more than fat, leads to metabolic and nutritional defects, immunodeficiency, coagulopathy, malnutrition and death.

@ because it is bacteriostatic and non- irritating, it does not cause fibrothorax.


Etiology

1. Trauma.2. Tumor.3. Miscellaneous.4. Idiopathic.


Surgical Trauma1. Cardiovascular surgery (coronary

artery by-pass when the internal mammary artery is harvested; heart transplant, high lumbar aortography).

2. Esophageal surgery( sclerotherapy for esophageal varices).

3. Pulmonary surgery.4. Costo-vertebral surgery.


5. Neck surgery (thoracic-lumbar fusion for correction of kyphosis).

6. Diaphragm surgery.


Non-surgical Trauma1. Blunt chest trauma.2. Hyperextension of the spine or

fracture of a vertebra.3. External cardiac massage.4. Aortic angiography.5. Sub-clavian vein

catheterization.


6. The injury may be less impressive,and chylothoraces have been attributed to coughing, vomiting, and weight lifting, or vigorous stretching while yawning.


Chylothorax secondary to closed trauma is usually on the right side, and the site of rupture is most commonly in the region of the ninth or tenth thoracic vertebra (e.g. fall from height, motor vehicle accidents, compression injuries to the trunk, heavy blows to the back or stomach, and childbirth).


Tumors


Fifty percent of chylothoraces in adults are caused by tumors.

Seventy f ive percent are lymphomas.

Other forms include chronic lymphocytic leukemia, metastatic disease and lung cancer.


Benign and malignant tumors may involve the TD through lymphatic permeation, direct invasion or tumor embolus.


Miscellaneous1. On rare occasions, a

chylothorax is associated with heart failure or nephrotic syndrome and the effusion is a transudate.

2. Liver cirrhosis.3. Thrombosis of the SVC or the

subclavian vein.


4. Primary lymphangioleiomatosis (LAM).

5. Tuberus sclerosis.6. Lymphangiomatosis.7. Sarcoidosis.8. Yellow nail syndrome.9. Tuberculosis.


10. Amyloidosis.11. Castleman’s disease (Giant

Lymph Node hyperplasia).12. Familial lymphedema.13. Hypothyroidism.14. Obstruction of the SVC

secondary to Behcet’s syndrome.


15. Filariasis.16. Radiation-induced

mediastinal fibrosis.17. Kaposi sarcoma in AIDS

patients.18. Gorham’s syndrome.


Congenital ChylothoraxIt is the most common cause of

pleural effusion in the newborn infant.

Is twice as often in males.Prognosis is good and perinatal

morbidity is between 15-30%.The infant develops respiratory

distress in the first few days of life.


In some cases, a congenital chylothorax is associated with Turner’s syndrome, Noonan’s syndrome, or Down’s syndrome.


Clinical


The main danger to patients with chylothorax is that they become mal- nourished and immuno-compromised because of the removal of large amounts of protein, fat, electrolytes and lymphocytes from the body with repeated thoracentesis and chest tube drainage.


The loss of chyle might result in hyponatremia, hypocalcemia, acidosis, hypovolemia, reduction of venous return to the heart, and lymphocytic depletion.


With non-traumatic chylothorax, the onset of symptoms is usually gradual.

The init ial symptoms of chylothorax are usually related to the presence of space occupying fluid in the thoracic cavity e.g. dyspnea.

Pleural chest pain and fever are rare.


A latent period of 2-10 days usually occurs between the trauma and the onset of the pleural effusion.

Lymph collects extrapleurally in the mediastinum after the initial duct disruption, forms a CHYLOMA, and produces a posterior mediastinal mass.


The mediastinal pleura eventually ruptures, chyle gains access to the pleural space, and dyspnea is produced by the chyle compressing the lung.

At times, hypotension, cyanosis, and extreme dyspnea occur when the chyloma ruptures into the pleural space.


Diagnosis


Lipid measurements might be indicated in all patients with pleural effusion of unknown etiology in order to rule out the diagnosis of chylothorax.


High levels of lipid accumulate in the pleural space in two situations:

* When the thoracic duct is disrupted, chyle can enter the pleural space to produce a chylous effusion.


* In long standing pleural effusions, large amounts of cholesterol or lecithino- globulin complexes can accumulate in the pleural fluid to produce a chyliform pleural effusion.


Chyle or Pus? Chyle may be mistaken for

pus but there is no odor and the cultures are negative.

Gram stain reveals lymphocytes rather than PMLs with no bacteria.


The milkiness with empyema is caused by the suspended white blood cells, and debris and if such fluid is centrifuged, the supernatant is clear.


The best way to establish the diagnosis of chylothorax is by measuring the triglyceride and cholesterol levels in the pleural fluids.


If the pleural fluid triglyceride level is above 110mg/dL and the ratio of the pleural fluid to serum cholesterol is less than 1.0, the diagnosis of chylothorax is established.


The cholesterol ratio is used to exclude pseudochylothorax because some patients with chyliform pleural effusion also have triglyceride levels above 110 mg/dL, but their pleural fluid to serum cholesterol ratio will exceed 1.0 .


NB/ the only other situation in which the pleural fluid triglyceride is above 110mg /dL is when IV fluid containing high levels of triglycerides leaks from a central vein into the pleural space.


Chylomicrons

The demonstration of chylomicrons in the pleural fluid by lipoprotein analysis establishes the diagnosis of chylothorax.


Lipophil ic Dye Ingestion

Ingestion of a fatty meal with a lipophilic dye, followed by a thoracentesis 30 to 60 min later, to ascertain whether the pleural fluid has changed in color.


With congenital chylothorax, the pleural fluid is initially serous and turns chylous only when milk feedings are started.


Lympho-scintigraphy Technetium-99m human

serum albumin is injected into the dorsum of the foot or hand and subsequently the thoracic duct is imaged in nuclear medicine.


Oral ingestion of iodine labeled BMIPP, and after ingestion of this tracer by approximately 80 minutes the thoracic duct can be imaged.


Treatment


The general aims are:

1. Relief of dyspnea by removal of chyle.

2. Preventing dehydration.3. Maintenance of nutrition.4. Reduction in the rate of

chyle formation.


Conservative Treatment Tube drainage. Medium-chain fatty acid diet. NOP and total parenteral

nutrition (TPN) is the most effective method of decreasing chyle production.

Fluid and electrolyte support.


Decrease f low of chyle The patient’s nutritional status

can be maintained with IV hyper-alimination. This is preferred than medium-chain triglycerides which are unpalatable and are recommended when one wishes to reduce the flow of chyle.


The flow of chyle is also decreased if the patient stays in bed because any lower extremity movement increases the flow of lymph.


Somatostatin

oIt requires continuous IV infusion.

oUsual starting dose is 3.5mg/kg/hr which can be increased to 10mg/kg/hr.


Octreotideo It is given by SC route.o Usual dose in the adult is 50mg/8

hrs, in children 0.3-1mg/kg/hr.o Primary side effects include

suppression of GIT motility and secretion (loose stools, malabsorption, nausea and flatulance).


Mechanism of action

They decrease triglyceride absorption and lymphatic flow.


One must treat the chylothorax definit ively, such as with thoracic duct ligation or pleuroperitoneal shunt implantation, before the patient becomes too cachectic to tolerate the operation.


Pleuroperitoneal Shunt• The optimal method to remove

chyle.• Chyle is shunted to the peritoneal

cavity where it is absorbed without creating significant ascitis.

• It can be inserted with local anaesthesia as opposed to general anaesthesia which is required for thoracic duct ligation.


• The shunt can be removed 30-90 days after its insertion.• No dietary restriction is

needed.• Should not be inserted if

chylous ascitis is present.


Percutaneous Transabdominal Thoracic

Duct Ligation


• Minimally invasive.• Pedal lymphography is

initially performed to opacify large retroperitoneal lymph channels.


A suitable duct (>2 mm diameter) is punctured transabdominally to allow catheterization and embolization of the thoracic duct under fluoroscopic guidance.


The embolization is performed using platinum microcoils or micro particles.

Glue may be used singly or in combination with coils.


Pleurodesis Pleurodesis through a chest

tube is not generally recommended for patients with chylothorax.

Thoracoscopy with talc insufflation of 2gm talc or with pleural abrasion or partial parietal pleurectomy is done and is effective.


Ligation of Thoracic DuctUntil Lampson initially

described successful ligation of the thoracic duct in 1948, the mortality rate from chylothorax was 50%.

It is the definitive treatment.


Causes no ill defects (because of the multiple anastamosis among various lymphatic channels and direct lymphatico-venous communications.

If the chylothorax is bilateral, a right thoracotomy should be performed because the duct is more readily approached from that side.


The actual point of leakage from the duct must be determined and ligation of the duct on both sides of the leak is done.

Preoperative lymphangiogram should be done.


Chyliform Pleural Effusion

Is a pleural effusion that is turbid or milky from high lipid content not resulting from disruption of the thoracic duct.


Pseudochylothoraces may be seperated into those with cholesterol crystals (pseudochylous effusions), and those without cholesterol crystals (chyliform pleural effusions). But no practical reason exists for making this distinction.


Most patients with chyliform pleural effusion have long standing pleural effusion (mean >5y), and have thickened and sometimes calcified pleura.


Most of the cholesterol in chyliform PE is associated with high-density lipoproteins in contrast to the cholesterol in acute exudates that is mostly bound to low-density lipoproteins.


The origin of cholesterol and other lipids is not definitely known, but one possibility is from degenerating RBCs and WBCs in the pleural fluid.


Causes The two most common

causes of the effusion initially are rheumatoid pleuritis and tuberculosis.

Many pleural effusions secondary to paragnomiasis contain cholesterol crystals.


Chyliform effusions are usually unilateral.

Differential diagnosis of chyliform pleural effusions are empyema and chylothorax.

In an empyema, centrifugation results in a clear supernatant.


Chyliform pleural effusions contain cholesterol crystals. Microscopically, the cholesterol crystals present a typical rhomboid configuration.

Pleural fluid cholesterol levels > 200 mg/dL strongly suggest a chyliform effusion. Some have a high (>250mg/dL ) trigyceride level.


When a patient is diagnosed as having a chyliform pleural effusion, the possibility of TB should always be entertained.

Decortication should be considered if the patient is symptomatic and the under- lying lung is believed to be functional.


Pleurectomy If the thoracic duct cannot be

successfully ligated at thoracotomy, a parietal pleurectomy should be performed to obliterate the pleural space.

One must not delay thoracotomy too long.


Role of Thoracoscopy Ligation of the thoracic duct is

done with the videothoracoscope.

Thoracoscopy permits the entire pleural space to be visualized, as well as allowing direct suture of a lymphatic leak.


References

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Hamdan MA, Gaeta ML: Octreotide and low-fat breast milk in postoperative chylothorax. Ann Thorac Surg; 77:2215 (2004).

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Demos NJ et al.: Somatostatin in the treatment of chylothorax. Chest; 119: 964 (2001).

Kalomendis I: Octreotide and chylothorax. Cur Opin Pul Dis; 12:264 (2006)

Little AG et al.: Pleuroperitoneal shunting: alternative therapy for persistent chylothorax. Ann Thorac Surg; 208:443 (1988).


Adler RH, Levinsky L: Persistent chylothorax. J Thorac Cardiovasc Surg; 76: 859 (1978).

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Perry RE et al.: Pleural effusion in the neonatal period. J Pediatr 62:838 (1963

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chylothorax

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