Discussion
Bochdalek hernia, a form of CDH, results due to a defect in the pleuroperitoneal membrane with herniation of the abdominal contents [6]. Baglaj et al. reviewed the details of 362 children with late presenting CDH and observed that the left posterior hernia was the dominant type found in 79.4 % of the CDH patients, the male to female ratio was nearly 2:1 in both the left and right-sided CDH, and the true hernia sac was found only in 32.7% of the patients [2]. Patients with late presenting CDH may remain completely asymptomatic and the diagnosis may be incidental, or they may present with acute or chronic gastrointestinal symptoms or less commonly, respiratory symptoms [7]. The presence of a hernia sac has been suggested as one of the risk factors for the development of postoperative chylothorax. The study by Kavvadia et al. showed that two out of three infants who had hernia sac developed postoperative chylothorax, and it was most likely because of the injury to the lymphatic vessels when the sac was excised [8, 9]. However, hernia sac was not evident in our patient. Even in the absence of a sac, vigorous perioperative manipulation and subsequent trauma to the lymph vessels related to the diaphragm may have resulted in chylothorax in our patient.
The diagnosis of chylothorax is made if the drained fluid is whitish, and the value of triglycerides in the fluid is >110 mg/dl [5]. In the presented case, the drained fluid was milky, and the value of triglycerides in the pleural fluid was 210 mg/dl. In case of any doubt or uncertain diagnosis, the intake of a meal rich in fats by mouth or nasogastric tube results in a dramatic change in the color of the pleural fluid confirming the diagnosis of chylous effusion. Also, pleural fluid leukocyte count comprising more than 90% lymphocytes is a useful and independent marker of chylous effusion [10], and the pleural fluid analysis in our patient also yielded a similar finding. Our case report highlights the fact that effusion that occurs earlier may remain colorless for a few days. Clear and light yellow colored chyle may be observed if the patient has not been properly fed [11]. With time and gradual introduction of enteral feeds, it turns milky. Hence, for effusions that remain persistent, chylothorax should be one of the differential diagnoses, even if the fluid appears clear.
There is no consensus on whether to manage postoperative chylothorax with conservative management or surgery for a particular value of intercostal drain output [12]. Stringel et al. suggested mass ligation of the thoracic duct just above the diaphragm for chylous effusion >15ml/kg/day [13], whereas other reports favor surgery only for chylous effusion > 100 ml/kg/day [14]. Hence, keeping aside the absolute value of chest tube drainage, patient management should be based on clinical judgment [15]. Conservative management in the form of continuous chest tube drainage and cessation of enteral feeds for some time to decrease the lymphatic production followed by nutritional support in the form of TPN and MCT diet and the use of octreotide along with prophylactic antibiotics for hastening the resolution of chylous effusion have been suggested in the literature [5, 9, 12, 15-19]. Casaccia and colleagues found thoracic lymphatic vessel damage to be the major cause of chylothorax after CDH repair, and chylothorax of such etiology resolved medically in their entire study cohort. The duration for resolution of chylothorax ranged from 4 to 34 days, and the mean duration of TPN in this study cohort was 13 days [17]. Those who fail to respond to conservative management with a persistently increasing chest tube drainage should undergo some form of surgery (thoracic duct ligation, pleurodesis, placement of pleuroperitoneal shunt) [5,15].
Postoperative chylothorax following CDH repair may be complicated by infection. There is a significant risk of hypoproteinemia and leukopenia due to the loss of chyle. However, a study by Allen et al. showed no correlation between the circulating lymphocytes and the occurrence of an infectious complication. Hence, antibiotics should not be used based solely on the lymphocyte count [15, 20]. In our case, the patient did not show any infectious complication except for one spike of fever as she was kept on prophylactic antibiotic empirically. She had a good appetite and weight gain.
There was no significant difference in the rate of survival among patients with chylothorax versus no chylothorax. However, the length of hospital stay and the number of days on a ventilator is significantly increased in patients with chylothorax [15]. We decided to choose the conservative modality of management in this patient who had a chylous effusion output up to 26ml/kg/day in the form of continuous chest tube drainage, broad-spectrum antibiotics, intravenous albumin infusion, and nil per os for three days, followed by a high-protein and low-fat diet. Eventually, the chylothorax in our patient resolved without operative intervention in 4 weeks.