Introduction

Chylothorax is defined as the presence of chyle in the pleural space. It is an uncommon complication after neck dissection but has a significant morbidity and mortality rate [1]. Chyle leaks can be identified either during surgery or in the first few days following surgery by observing increased lymphatic fluid buildup in the drainage. To achieve proper management, the diagnosis should be done early as chyle leak can affect the healing process and lead to poor wound healing, electrolytes disturbances, and cardiopulmonary complications [2, 3].

Bilateral chylothoraces are an even rarer entity with incredibly limited reports in available literature, in which chyle infiltrates the pleural space bilaterally. Neck dissections are surgical procedures used to both diagnose and treat cancer in the head and neck region. In general, a neck dissection should be used to treat any disease with clinically positive nodes or advanced tumors in node negative disease [4].

Due to the rarity and limited information available on bilateral chylothoraces, we intend to provide further understanding of the condition by systematically reviewing the available literature and discussing the management, investigations, and treatment modalities of the condition alongside proposing a management algorithm.

Methods

A systematic search using the databases of PubMed, Embase and Web of Science was conducted, looking for all articles reporting cases of bilateral chylothoraces. The search terms included “bilateral chylothorax” and “chylothorax” and the review period was restricted from January 1, 1955, to June 1, 2023. Each abstract was screened for possible inclusion by two reviewers independently (S.H, J.H). Articles were only included if both reviewers independently determined that all inclusion criteria were met. If a consensus was not reached, a third author was consulted. Two authors performed data extraction (F.I, A.A).

Inclusion/Exclusion Criteria

Inclusion criteria included all levels of scientific evidence, any treatment option, human studies, both genders and any age group. The following criteria were used for exclusion: articles of unrelated diagnosis, articles available in abstract form only and non-English articles.

Intervention

Any treatment strategy for bilateral chylothoraces, including conservative, medical, surgical, and any other interventions.

Comparator/Control

No comparison or control group was required for inclusion in this review.

Primary Outcomes

Studies were required to report clinical presentations and the type of neck dissection done and the treatments and interventions used to manage the condition. Ideally, studies provided the length of stay in the hospital quantified by postoperative days spent as an inpatient.

Secondary Outcomes

We also extracted data on the duration it would take for the bilateral chylothoraces to resolve or significantly improve following treatment or intervention, alongside extracting data on the outcomes of the provided management. The data was extracted and then quantitatively and descriptively documented in Table 1.

Table 1 Table highlighting available cases of bilateral chylothoraces
Full size table

Statistical Analysis

Highly heterogeneous results were anticipated secondary to significant variations in hospital protocols, treatments, and initial neck dissections done. Data pertaining to treatments and patients’ responses to such were extracted. If a specific post-operative date of discharge was acquired, it was then extracted and summarized in Table 1. We were unable to conduct a meta-analysis due to the significant limitations of studies and the heterogeneity of the included studies in terms of presentations, unique hospital protocols, and treatments alongside limited sample size.

Risk of Bias Assessment

Studies of all different types (case reports, case series, cohort, case–control and interventional studies) were included. For this reason, no specific quality assessment tool was used. Data that is unclear or ambiguous or that did not satisfy the inclusion criteria were excluded from analysis.

Results

A total of 37 cases were found. The earliest report of chylothorax post-neck dissection was in 1951, while the latest was reported in 2018. A total of 5 cases were reported twice during 2007 and 2013. In terms of cases’ characteristics, the mean age for all included participants was 51.4 ± 16.5 years. The youngest case was 17 years old while the oldest was 78 years. About 73.0% of cases were female (n = 27) while 27.0% were male (n = 10), as depicted in Table 1.

The most common sites of primary lesions were related to papillary thyroid carcinomas (43.2%). Other common sites included SCC of the larynx (8.1%), of the oral cavity (8.1%), and the supraglottis (8.1%).

Neck dissection was performed on the left side in 48.6% of cases, while 45.9% had bilateral neck dissections. Only 2 cases had a central and left neck dissection (5.4%). The majority of neck dissections were modified radical dissections (27.0%). Among operated patients, only 40.5% had an intraoperative chyle leak detected and repaired.

Amongst the included cases, x-rays were the most common modality for diagnosis (54.1%). On the other hand, CT scans and CT in combination with x-rays were utilized in 8.1% and 16.2% of cases, respectively. Ultrasound diagnosis was utilized only once among the 37 included cases. With respect to treatment, Drainage followed by TPN was the most utilized treatment modality (37.8%).

Surgical treatment was utilized in 10 cases, 50% used lymph node embolization while the other 50% used lymph node ligation. Fortunately, irrespective of treatment, resolution was achieved in all cases. Time to discharge ranged from 2 to 40 days.

Discussion

Chylothoraces secondary to neck dissections occur either iatrogenically or due to inflammatory reactions secondary to direct leakage of the thoracic duct [5]. Another cause is secondary to the unintentional ligation of the thoracic duct, leading to the eventual rupturing of the thoracic duct [6]. When a patient who recently underwent neck dissection presents with a pleural effusion, a chylothorax should be suspected [7]. Many chylothoraces may initially be treated as cases of fluid overload [8]. This may prolong management until a thoracentesis is ordered; thus correctly diagnosing the condition [9], highlighting the importance of keeping the entity as a differential diagnosis [10].

Upon draining the milky fluid, investigations that aid in the diagnosis of the entity include Sudan III/IV staining, triglyceride quantification, and lipoprotein electrophoresis to detect any chylomicrons. Triglyceride levels of > 110 mg/dL strongly suggest the presence of chyle in the sample [11]. Serial chest radiographs should then be utilized to monitor the progression of the discovered entity [9].

Management of a chylothorax can be achieved via numerous methods ranging from dietary modifications to the use of various medications or the utilization of minimally invasive interventions and surgical ligation of the thoracic duct. Approaches to managing the condition include dietary modifications to correct electrolyte imbalances, chemical pleurodesis with the thoracostomy tubes, and thoracic duct ligation [12].

Dietary modifications in managing the condition include placing the patient on a low-fat diet (< 10 g a day), medium-chain triglyceride diet, and total parenteral nutrition in that sequence [12]. Medications such as Somatostatin, Octreotide, and Midodrine to prevent chyle formation have also been reported to be helpful in managing the entity [13, 14]. Alternative managements such as injected fibrin glue have limited supporting data [15]. Surgical techniques which include pleurovenous shunting, pleuroperitoneal shunting, and thoracic duct embolization also report successful outcomes [16, 17]. Most patients will benefit the most from a step-wise approach of conservative approaches to more invasive interventions if required [18]. Failing to manage the condition conservatively leads to the need for surgical interventions. Uchida et al. discovered that intervening in the early postoperative stage without pleurodesis yielded best results on patients who drained more than 500 ml/day despite being on a low fat diet; therefore surgical intervention must be early for cases of persistent chyle leakage [19].

The clinical guidelines that determine the mode and criteria for surgical interventions for prolonged chyle leakage is variable amongst institutions, with some suggesting that chest drains of over 1500 ml/day in adults or 100 ml/kg body weight in children or chyle leakages at rates of more than 1000 ml/day for 5 days, or chyle leaks that extend more than 2 weeks in duration, are appropriate criteria for surgical intervention. [20,21,22,23].

In the extracted data in Table 1, 27 patients were managed conservatively whilst 10 required surgical interventions. The majority of conservative interventions started off with dietary modifications and the insertion of thoracotomy tubes, with Octreotide being added as an adjuvant for some patients. Interventions were started immediately or within 24 h of discovering the condition via investigations. Most non-surgical patients were discharged within two weeks of management and all had eventual resolution of their symptoms. Of the surgical patients, a majority of the procedures involved thoracic duct ligation as the mainstay approach after re-exploration was done, with interventions generally occurring within 12–48 h after starting conservative managements. All patients achieved resolutions of their symptoms.

The limited sample size makes it difficult to highlight trends in the outcomes of patients based on the intervention used. This data demonstrates, however, the viability of all treatment methods if a reasonable step-wise approach is appropriately followed.

The aforementioned variability in management protocols would be aided by a management algorithm in treating bilateral chylothoraces which will be relevant to and apply to the management of unilateral chylothoraces, as demonstrated via a flow diagram in Fig. 1.

Fig. 1
figure 1

Proposed algorithm in treating bilateral chylothoraces

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Conclusion

Bilateral chylothoraces post-neck dissections are an incredibly rare entity and have only been reported in less than 50 cases in available literature. In patients in which there is no obvious chyle leak, it is imperative to consider bilateral chylothorax as a differential in a patient with a postoperative pleural effusion that is non-responsive to diuresis, and to investigate for it accordingly.

Managing the condition involves a multidisciplinary approach that employs both medical and surgical investigations for post-operative patients. This is provided in a stepwise approach for patients that is provided in a multidisciplinary manner.