Right lung atelectasis secondary to endobronchial invasion

Clinical History

Patient, with known history of metastatic melanoma, with cerebral, paratracheal and right hilar metastasis, presents cough, expectorations and dyspnoea increasing with effort.

Imaging Findings

The posteroanterior chest radiograph shows right atelectasis (Fig. 1a-b) with mediastinal shift to the right and pleural effusion. Previous chest radiographs and enhanced chest CT showed upper mediastinal enlargement related to the melanoma’s paratracheal metastasis (Fig. 2a-e). Occlusion of the upper right lobar bronchus by metastatic extrinsic compression or endobronchial invasion was suspected. Enhanced chest CT confirmed the progression of the necrotic mediastinal and right hilar mass with distal tracheal and right bronchus tumoral invasion (Fig. 3a-c) leading to complete right lung atelectasis. Invasion of the superior vena cava without complete occlusion was noted (Fig. 3d-e). The mass encased upper lobar branches of right pulmonary artery (Fig. 3d). The stricture was treated by a Y tracheobronchial metal prosthesis. A second non-enhanced chest CT was performed few days later, since the patient developed inspiratory stridor and dyspnoea, which showed sub-occlusive filling of right and left sleeves of the stent (Fig. 4a-b), probably due to mucoid impaction.

Discussion

Atelectasis is collapse of lung tissue, seen on chest radiograph as an opacity with direct and indirect signs, like mainly displacement of fissures, crowding of vessels, diaphragmatic elevation, mediastinal shift and compensatory overinflation. Four mechanisms may be involved such as resorption, relaxation, adhesive and cicatricial atelectasis. The obstructive atelectasis is caused by airway obstruction and resorption of alveolar gas. It occurs more rapidly if patients receive pure oxygen or in presence of endobronchial lesions acting as a one-way valve [1]. The typical clinical presentation of central airway stenosis is stridor and inspiratory bradypnoea, but atypical presentations are frequent.
In our case, the stenotic right main bronchus is invaded by a metastatic lesion, which is a frequent cause of airways stenosis. In general, those tumours are inoperable because they are classified as advanced stage [2].
There are many indications for airways stenting, like persistence of secondary or primary malignant tracheobronchial obstruction despite endobronchial dilatation, post-intubation or post-tracheotomy subglottic stenosis in spite of treatment [3].

Our patient was treated with a Y tracheobronchial metal prosthesis because of her late stage. The stent varies in size and the main types are made of silicone, metal or both. Silicone stents are the most frequently used but have the disadvantage to migrate more commonly than the other types, requiring repeated bronchoscopy. Metal stents migrate less frequently but have high risk of perforating due to their expansible force and to block secondary to tumoral or granulation tissue growth [3], usually treated with corticosteroids. Self-expanding metal stents are used when there is an airway stricture which cannot be dilated prior to stent insertion. In our case, the stent was blocked probably secondary to mucoid impaction.

Chest radiograph is initially used to diagnose atelectasis [4]. High resolution enhanced chest CT helps in identifying the atelectatic lobe, the cause of atelectasis and to exclude other complications, such as vascular invasion. Bronchoscopy is indicated in patients with an airway stent to ensure appropriate stent positioning and stent patency in case they develop unusual respiratory symptoms. Serious complications such as local inflammation with obstruction of the stent, migration of the stent or airway perforation are rare but must be supported quickly [3]. If the patient is haemodynamically stable and there is enough time, then enhanced high resolution chest CT is required.

Differential Diagnosis List

Final Diagnosis

Right main bronchus metastatic invasion

URL:	https://www.eurorad.org/case/12183
DOI:	10.1594/EURORAD/CASE.12183
ISSN:	1563-4086