Key words : Children, Chyle, Liver disease, Surgical intervention

Introduction

Chylothorax is a type of pleural effusion charac-terized by the accumulation of chyle, resulting from leakage from the lymphatic vessels, most commonly the thoracic duct.¹ Because 1.5 to 4 liters of chyle is transported through the lymphatic system every day, disruption of the thoracic duct may cause rapid accumulation of fluid in the pleural space, leading to life-threatening consequences.¹

The etiology of chylothorax can be classified into traumatic and nontraumatic causes, with traumatic causes further subclassified as iatrogenic and noniatrogenic. Nontraumatic causes include malig-nancies and systemic diseases such as sarcoidosis, tuberculosis, amyloidosis, superior vena cava thrombosis, congenital duct abnormalities, and diseases of lymph vessels. Noniatrogenic traumatic chylothorax may result from blunt or penetrating trauma, where trauma directly damages the thoracic vessels or causes tissue damage. Sudden hyperex-tension of the spine may result in the obstruction of the lymph flow and further leakage and rupture of the duct.²

Postoperative chylothorax is the most common type among traumatic etiologies, and the leading cause is esophagectomy, with a reported incidence of 0.2% to 10.5%.3 Thoracic surgeries may cause chylothorax in 1% of patients.⁴ Other causes of iatrogenic chylothorax include subclavian vein catheterization and central venous catheterization-related venous thrombosis, which may obstruct the thoracic duct flow. Because the risk for chylothorax increases with the extent of surgical trauma, it can be implied that transplant surgeries should also be considered as potential causes for chylothorax development. Chylothorax following liver transplant (LT) is a rare entity, and its etiology requires more thorough research.

Two cases of chylothorax following pediatric LT, which were successfully managed conservatively, were discussed in this report. The study was conducted according to the criteria of the Declaration of Helsinki 1975 and the Declaration of İstanbul 2008. It was performed as a retrospective study with anonymized data analyses and not requiring ethical committee approval.

Case Report

Patient 1
An 8-month-old male patient with diagnosed progressive familial intrahepatic cholestasis type 2, clinically evident by generalized jaundice, presented for a living donor LT (LDLT). His Child-Pugh-Turcotte score was 7B, and his pediatric end-stage liver disease score was 20. The medical history of the donor was unremarkable.

The patient underwent left lateral segment LDLT. The 27-year-old male donor was the father of the patient. Roux-n-Y technique was performed for biliary reconstruction. The explant pathology report revealed an incidental 6-mm hepatocellular carcinoma. The patient was discharged uneventfully on postoperative day 11.

Twelve days after discharge, the patient was admitted to the emergency room with fever and was hospitalized immediately. The patient developed tachypnea and intercostal retractions. Chest radiog-raphy demonstrated evidential right pleural effusion. Pleural fluid drainage was performed via percutaneously placed 6F catheters. The milky-colored fluid was considered to be chylothorax. Thoracentesis analysis revealed triglyceride levels of 141 mg/dL. Zero-fat diet and total parenteral nutrition were initiated. After 2 days of daily pleural fluid drainage of 110 to 135 mL, somatostatin intravenous infusion was added to the therapy. On day 4 of conservative management, pleural drainage yielded no fluid; chest radiography also did not demonstrate fluid levels (Figure 1).

The patient showed no positive microbiological culture on blood or pleural fluid samples. Oral diet included medium-chain triglyceride (MCT) formula was initiated on day 5 of therapy, and somatostatin dose was cut in half. Somatostatin was discontinued on day 7, and the patient was discharged uneventfully.

Patient 2
A 15-month-old male patient with citrullinemia type I and noncirrhotic liver characterized by hyperam-monemia episodes presented for a LDLT. The patient underwent LDLT using the left lateral segment. The 35-year-old male donor was the father of the patient. Roux-n-Y hepaticojejunostomy was performed. Posto-perative period was unremarkable, and the patient was discharged uneventfully on postoperative day 14.

On postoperative day 18, the patient presented with fever and shortness of breath and was hospitalized. Pleural effusion was detected using ultrasonography, and right-sided pleural effusion was confirmed on a plain chest radiography. A 6F pleural catheter was placed percutaneously, and pure chylous fluid was drained. Triglyceride level was 173 mg/dL. Conservative management, including zero-fat diet, total parenteral nutrition, and somatos-tatin therapy was initiated.

Pleural catheter yielded pleural fluid for the following 22 days, with volumes ranging from 45 to 530 mL/day. The patient showed no positive micro-biological culture on blood or pleural fluid samples. After cessation of pleural fluid drainage, the pleural catheter was removed, and somatostatin dose was cut in half. Oral diet including MCT formula was started. The patient was discharged on day 25 of therapy, following the resolution of chylothorax (Figure 2).

Discussion

The thoracic duct enters the posterior mediastinum through the aortic opening of the diaphragm and shifts to the left and runs in the posterior mediastinum behind the aortic arch, at the level of fifth thoracic vertebra. This anatomy occurs in approximately 60% of the population, as embryological variation may result in multiple thoracic duct branches.⁵ The primary role of the duct is to carry 60% to 70% of the ingested fat into the venous system at a flow of ~100 mL/hour, with two-thirds of the chyle generated by the intestines and liver. Apart from the ingested fat, chylous fluid also contains immunog-lobulins, digestive products, enzymes, and white blood cells (400 and 6800 cells/mL), the majority of which are T lymphocytes.⁶

Clinically, chylothorax can present with chest pressure and progressive dyspnea, following a latency period of 4 to 23 days.⁷ Loss of serum albumin, total protein, electrolytes, and predo-minantly T lymphocytes may lead to a state of malnutrition and impaired immunity. The diagnosis of chylothorax is confirmed by triglyceride levels >100 mg/dL or the presence of chylomicrons on fluid analysis.⁸

Chylothorax after abdominal surgery, including LT, is extremely rare.^4,9 One report in the literature described a case of chylothorax in a recipient after LT. The authors proposed that the cause of chylothorax could be attributed to the inadequate closure of the communication between the pleural and peritoneal cavities after transdiaphragmatic thoracentesis of hydrothorax intraoperatively.¹⁰ During abdominal surgery, especially in surgeries for oncological cases, lymphadenectomies may reveal multiple damaged lymphatic vessels. In case of such a lymphatic injury, pleural negative pressure may lead to the migration of the lymphatic fluid via any diaphragmatic opening or surface.¹⁰ This appears to be the same mechanism considered in hepatic hydrothorax.¹¹

Remarkably, in contrast to the transdiaphragmatic migration hypothesis, our patients developed chylothorax with no evidence of chylous leaks in the intra-abdominal cavity. Similar to our patients, a report of a case from China described a chylothorax without chylous ascites in a right lobe living donor. The patient’s chylothorax was completely resolved in 12 days with conservative treatment.⁹ In such cases, using a fixed abdominal retractor system during hepatectomies may lead to over-traction and injuries to the thoracic duct and may act as a leading point of chylothorax development.

Presently, no single gold standard treatment has been described for postoperative chylothorax. Conservative management options, including efficient drainage of the pleural fluid, total parenteral nutrition, and fat-free diet together with MCT supplementation, are usually the first-line treatment modalities and are usually effective.¹² Etilefrine, an ?- and ?-adrenergic sympathomimetic drug used in postural hypotension, has been proposed as an additional conservative method.⁷ Conservative techniques may be continued for up to 4 weeks.¹²

The sources of uncontrolled lymphatic leakage may be demonstrated by lymphangiography.⁴ Lymphangiography is considered as the gold standard for investigating chylothorax but is a complicated procedure that may cause tissue necrosis and embolism. Lymphoscintigraphy with labeled human albumin, dextran, or any nano colloid is quick, minimally invasive, and does not have any known side effects.^4,12 These techniques may reveal the damaged lymphatic vessels.In general, surgical interventions bring about better results than conservative management when daily chyle leak exceeds 1 L/day for more than 5 days or 1.5 L/day in an adult or >100 mL/kg body weight per day in a child and/or when chyle flow persists for more than 2 weeks.¹³ Surgical intervention is usually performed as video-assisted thoracic surgery, during which leakage locations of the duct may be visualized and sealed.

Computed tomography-guided lymphatic duct occlusion with N-butyl cyanoacrylate glue may be performed in persistent cases.¹⁴ Pleurovenous shunting is an appealing treatment alternative for nonmalignant pleural effusions and is a short and easy procedure, which can also be performed in high-risk patients. The shunt has a long-term patency and can provide efficient control of the effusions. In case of failure, replacement of the system or talc poudrage should be considered.15

In the patients described here, conservative management continued for 7 and 22 days respec-tively, with no need for further interventions.

Conclusions

Long-term conservative medical treatment should be the first choice in cases of chylothorax without chylous ascites following abdominal surgery in pediatric age groups. Most patients can benefit from this approach. The energy deficit that may occur during a low-fat diet may need to be supplemented with parenteral nutrition. Although interventional radiological and surgical options can be considered in persistent cases, complications that may develop during these procedures and technical difficulties in the pediatric age group should not be ignored.

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