Contrast-enhanced chest CT. Axial images.
Chest imagingCase Type
Anatomy and Functional ImagingAuthors
Malmierca P, Paternáin A, Calvo M, Ezponda A, García Baizán A, González de la Huebra Rodríguez I, I Rouilleault A, Bastarrika GPatient
54 years, male
A 54-year-old man with alcoholic liver cirrhosis, gastroesophageal varices and portal hypertensive gastropathy was admitted with decompensated cirrhosis.
As part of the study protocol to be included in the liver transplant list, the patient underwent a contrast-enhanced chest computed tomography (CT) examination. The CT study showed a very tortuous tubular structure, next to the thoracic aorta, representing a dilated thoracic duct, very likely due to decompensated cirrhosis and portal hypertension. Mild pericardial effusion and moderate perihepatic and perisplenic ascites were also found together with evident signs of chronic liver disease and portal hypertension.
The thoracic duct is the largest collecting lymphatic vessel. Lymphatics from the lower part of the body converge in the lumbar region to form the cisterna chyli, which, at the 12th thoracic vertebra, narrows and becomes the thoracic duct. It enters the thoracic cavity through the aortic hiatus, ascends to the right of the midline in the posterior mediastinum, crosses to the left of midline at the thoracic plane (T4-T6), continues superiorly through the thoracic inlet, and drains as a single trunk into the left subclavian vein [1-3].
The thoracic duct can be associated with various pathological conditions related either with impaired transportation or excessive production of lymph. In patients with liver cirrhosis and portal hypertension (as our patient), hepatic hilar lymphatics become distended due to the disturbance in the drainage from the sinusoid to the terminal veins. In decompensated cirrhosis, any rise in pressure in the portal system entails an increase in liver and splanchnic lymph production, responsible for thoracic duct dilatation. Other conditions, such as pancreatic obstruction or right-sided cardiac decompensation may also lead to an increase in the amount of thoracic duct lymph .
Although most radiological techniques may be limited to assess the morphology and course of the thoracic duct due to its hidden course or small diameter, CT can reliably depict its various appearances. In fact, multidetector-row CT has been shown to achieve almost 100% visualisation of thoracic duct, particularly after contrast administration, which helps differentiate the distal thoracic duct in the left supraclavicular area from adjacent structures .
Although the diameter of the thoracic duct can increase slightly during the lifetime, it is unlikely to be clinically or radiographically appreciable. However, patients with decompensated cirrhosis show a remarkable dilatation of the left distal thoracic duct (≥ 5mm). This fact seems to be significantly associated with disease severity. Little is known, however, about the prognostic significance of visibility of this anatomical structure on CT or if this radiological sign could be used to monitor disease progression .
In conclusion, the dilated thoracic duct can be incidentally detected on contrast-enhanced chest CT performed for the evaluation of cirrhosis-related intrathoracic disease. It usually appears as a tortuous and dilated tubular structure ascending in the thoracic cavity between the aorta and azygos vein to the right of the midline in the posterior mediastinum. A dilated thoracic duct (≥ 5mm) may be associated with the status of decompensated cirrhosis.
Written informed patient consent for publication has been obtained.
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