CASE 9577 Published on 02.12.2012

Mediastinal mass with air-fluid level

Section

Chest imaging

Case Type

Clinical Cases

Authors

Din I, Imran A, Irion K.

Royal Liverpool University Teaching Hospital; Email:islahu@yahoo.com
Patient

55 years, female

Categories
Area of Interest Mediastinum ; Imaging Technique CT
Clinical History
This 55-year-old woman presented with history of intermittent chronic cough. Physical examination was unremarkable.
Imaging Findings
Chest radiograph (Fig. 1) showed widened mediastinum with right paratracheal mass containing air-fluid level. Subsequent CT (Fig. 2) showed a hypodense non-enhancing mass in the right paratracheal region with extension into the subcarainal region. Air-fluid level was also demonstrated. A bronchogenic cyst was suspected; complicated in this case due to the presence of air-fluid levels. The cause for air-fluid level was not clearly evident in this case. Possibilities include infection or communication with the bronchial tree; the later being more likely as there were no clinical features to suggest infection. Histology results post excision confirmed the diagnosis of bronchogenic cyst.
Follow up chest radiographs at 6 months and 1 year later showed reduction in the size of the mediastinum with a persistent small area of air-fluid level (Fig. 3).
Discussion
Bronchogenic cysts are rare congenital malformations which result from abnormal budding of ventral foregut. They are usually mediastinal lesions, however, less common cysts may occur within lung parenchyma, pleura or diaphragm [1, 3]. They are lined by secretary respiratory epithelium and the wall is made of tissues similar to that of normal bronchial tree [3]. They do not usually communicate with bronchial tree and are therefore typically not air filled. Rather they contain fluid, variable amount of proteinaceous material, blood products and calcium oxalate [1]. These components result in increased attenuation mimicking solid lesions [3]. Possible complications of the cysts include fistula formation with the bronchial tree, superimposed infection, haemorrhage, malignant transformation and secondary bronchial atresia. Rarely, these cysts can lead to pleurisy, pneumothorax and air embolism [1, 3].

Bronchogenic cysts are usually asymptomatic and are found incidentally. When large, mass effect may result in bronchial obstruction and lead to symptoms of dyspnoea and cough [2, 3]. An alternative presentation may occur when cyst become infective [1].

On the plain radio-graphs, the cyst appears as soft tissue density rounded structures sometimes with air fluid level. CT is valuable in determining site, size and shape of cyst and typically shows well defined spherical mass of soft tissue or water attenuation. Most bronchogenic cysts can be confidentially diagnosed by using non-enhanced CT. However, administration of contrast material and MR help to differentiate it from surrounding structures and other masses. Variable attenuation on CT and signal intensity on MR with fluid levels have also been reported due to the presence of variable composition [3]. Definitive diagnosis is obtained by surgical excision and tissue biopsy [4].

Surgical excision is recommended to establish diagnose, alleviate symptoms and prevent complications in all operable candidates [2]. Transbronchial and percutaneous aspirations have been proposed as alternative to operation but these methods are not widely accepted because of possible cyst recurrence [4].

Teaching Point: Widened mediastinum on plain radiograph has a number of differentials. Most often, cross sectional imaging is required to narrow down the differential. Well defined rounded fluid density lesion with or without air fluid level in a relatively asymptomatic patient should prompt the diagnosis of bronchogenic cyst. As mediastinal abscess has high mortality, this must not be forgotten as a differential. Definitive diagnosis can be achieved with transbronchial or CT guided aspiration which are invasive and should ideally be planned after multidisciplinary team discussion.
Differential Diagnosis List
Bronchogenic cyst
Other congenital cysts/ malformations such as oesophageal duplication cyst and pericardial cyst
Mediastinal abscess
Final Diagnosis
Bronchogenic cyst
Case information
URL: https://www.eurorad.org/case/9577
DOI: 10.1594/EURORAD/CASE.9577
ISSN: 1563-4086