Evaluation of the left neck distal thoracic duct in cirrhosis with computed tomography

Abstract

Objective

To evaluate the left distal thoracic duct (DTD) in the lower neck area by using contrast-enhanced chest computed tomography (CT) in patients with liver cirrhosis (LC).

Methods

In 156 consecutive subjects who performed the contrast-enhanced chest CT, examinations were retrospectively reviewed. The diameters of the left DTD were measured by using CT. Depending on the diameter of the left DTD, the left DTD configurations were classified into four grades: grade 0 (no identification of DTD), grade I (diameter < 5 mm), grade II (diameters ≥ 5 mm and < 10 mm), and grade III (diameter ≥ 10 mm). Depending on the liver status, all 156 subjects were divided into three groups: (a) noncirrhotic liver group (n = 55), (b) compensated LC group (n = 88), and (c) decompensated LC group (n = 13).

Results

Among the 156 left DTD configurations, 81 (52%), 60 (39%), 10 (6%), and only 4 (3%) were assigned to the grade 0, I, II, and III, respectively. The noncirrhotic liver group included 45 (82%) grade 0 and 10 (18%) grade I subjects. The compensated LC group included 37 (42%) grade 0, 50 (57%) grade I, and 1 (1%) grade II subjects. In contrast, the decompensated LC group included 9 (69%) grade II and 4 (31%) grade III subjects.

Conclusion

When reviewed the contrast-enhanced chest CT, the left DTD can be identified more frequently in subjects with LC than in those with noncirrhotic liver. Furthermore, the degree of left DTD dilation may be associated with the severity of LC.

Introduction

Thoracic duct is the main and largest collecting vessel of the lymphatic system. The thoracic duct can be associated with various pathological conditions with impaired transportation or excessive production of the lymph [1], [2], [3], [4], [5]. In particular, liver cirrhosis (LC) can enhance the elevation of systemic venous pressure and hepatic lymph production, which may cause a distension of the thoracic duct in the lymphatic system [3], [5].

Visualization of the thoracic duct can be useful to enhance the understanding the underlying systemic disease related to the lymphatic duct dilatation. Most of the lymph formed from the liver leaves via hilar lymphatics and enters the thoracic duct [5], [6]. The thoracic duct shows substantial variability in terms of its course through the mediastinum and the cervical region [7], [8]. However, the thoracic duct drains the lymph from the lower half of the body and the gastrointestinal tract commonly into the large cervical veins. The left distal thoracic duct (DTD) in the left lower neck area has been considered as the end of the thoracic duct [8], [9]. Although most radiological techniques may be limited by hidden course or small diameter of the thoracic duct passing through the mediastinum, prior researchers reported that multidetector row computed tomography (CT) imaging can depict the various appearances of thoracic duct [2], [9].

In practice, the contrast-enhanced chest CT scan can be performed for evaluation of cirrhosis-related intrathoracic disease [10], [11]. The conventional chest CT scan would simultaneously describe the entire thorax, the liver, and the lower neck areas [12]. Prior several studies have reported that a dilated left DTD can mimic an enlarged cervical lymph node like a Virchow's lymph node [13], [14], [15]. To the best of our knowledge, however, the prevalence of the dilated left DTD under the LC has not been studied. Therefore, the purposes of the present study were to assess the visualization and diameter of the left DTD by the contrast-enhanced chest CT examinations depending on the presence of LC and to determine whether the dilatation of the left DTD may be associated with the severity of LC.