Congenital Chylothorax of the Newborn

Dear Editor,We wish to congratulate the authors for the important work of revision of the congenital chylothorax of the newborn (CCT) [1], a subject still much debated. We respectfully wish to make a few brief comments on the article. In general, CCT can be caused by dysplasia of the lymphatic system or by damage or ruptures of the thoracic duct due to trauma, surgery, malignancy, or cardiovascular disease. Lymph loss can manifest as chylothorax, chylous ascites, and chylopericardium or in various combinations. During the intrauterine period, the occurrence of these conditions singly or in combination can lead to the formation of hydrops [2]. The CCT pathophysiological mechanisms are very complex, including a disturbance in the transport of water between capillaries and extravascular tissues, or a decrease in plasma osmotic pressure and an increase in capillary permeability, or obstructed lymphatic flow [3].Pleural lymphatic function is critical for maintaining adequate lymphatic drainage [4]. The structure of the lymphatics differs between the visceral and parietal pleura. The lymphatic network that penetrates the lung parenchyma to join the bronchial lymphatic vessels is connected with the visceral pleural lymphatics. On the surface of the parietal pleura, the so-called stomata form the origin of the parietal lymphatics that drain the pleural fluid. Therefore, the function of the visceral and parietal pleura is very different.This premise drives the first question. The review states that 62% of cases were treated with in utero pleural drainage and that chemical pleurodesis was performed in 116 cases, using various agents. We would have expected a comment that if the effusion is due to functional causes (e.g., increased central venous pressure due to anemization), then a reversible condition, in utero drainage, is a useful procedure, while many doubts about pleurodesis arise, since the latter is a definitive procedure.We believe that pleural drainage in utero to facilitate breathing at birth and reduce the risk of pulmonary hypoplasia is the right choice, but we believe that extra caution must be exercised when considering prenatal pleurodesis. Table 2 is a bit confusing. Pulmonary hypoplasia is likely a consequence of effusion, but pulmonary lymphangiectasia is a cause [5]. Hygroma colli is reasonably connected to lymphatic dysplasia, often evidenced by increased nuchal translucency in the uterus [6], while BPD is probably related to mechanical ventilation, but is a consequence linked to many factors involved in the mechanical ventilation of the newborn. It is very important to point out that the evolution of CCT is very variable, at times decidedly benign, thus presenting a spontaneous resolution; it is therefore of fundamental importance to refer specific treatments to the diagnosis to avoid overtreatment. We partially disagree with the authors' proposed management of the CCT. Considering pleurodesis or thoracic duct ligation (or both) at weeks 5–6 is absolutely too early and, in our opinion, probably very dangerous. The data relating to the ligation of the duct reported in a total of 15 cases must be explained (reasons?). Surgical lesions of the thoracic duct, for example, in the case of surgery of the esophagus, may require ligation. But in the case of a possible congenital lymphatic dysplasia or a functional condition that determines the formation of chylothorax, the radical operation of ligation of the duct, obviously no longer reversible, could be more harmful than useful, regardless of the time decided for the surgery (5–6 weeks or more). It is easy to understand that both in the case of lymphatic dysplasia and in the case of a functional and therefore transient lymphatic imbalance, the exclusion of the function of the thoracic duct due to surgical ligation leads to a further reduction up to the possible arrest of the lymphatic flow. As previously commented on the use of pleurodesis, any intervention that is definitive must be carefully evaluated and, in our opinion, avoided during the neonatal period.The authors did not include clear arguments in Table 6 referring to instrumental examinations absolutely necessary in case of suspicion of congenital lymphatic dysplasia, such as lymphoscintigraphy or lymphangio-MR, just to name the most performed [7]. These instrumental tests are essential to establish the presence of congenital defect or functional imbalance. An observation period of 5–6 weeks should be considered too short if CCT due to functional imbalance is suspected. The possibility of spontaneous regression in these cases can also occur after 120–150 days [4], thus requiring great caution before making, or even just recommending, definitive solutions no longer modifiable, such as pleurodesis or thoracic duct ligation.The authors declare to disclose any possible conflicts of interest. There are no forms of support and financial involvement (e.g., employment, consultancies, honoraria, stock ownership and options, expert testimony, grants or patents received or pending, royalties), which took place in the previous 3 years, regardless of their potential relevance to the paper. There are no nonfinancial relationships (personal, political, or professional) that may potentially influence the writing of the manuscript. The authors have no conflicts of interest to declare.The authors have no funding sources to declare.The authors "C. Bellini, F. Boccardo, and T. Bellini" are responsible for conceiving the research and writing the article. All authors contributed equally to the article.