Recurring pneumothorax secondary to a ruptured bronchogenic cyst

Clinical History

A 38-year-old woman was referred to the emergency department with a 2-week history of progressive breathlessness with no chest pain. Past medical history of asthma. On examination she had reduced oxygen saturation (91%) on 2L oxygen, was slightly tachycardic (110 b.p.m.) and had reduced air entry in the left lung.

Imaging Findings

An urgent chest X-ray revealed a large left-sided pneumothorax with evidence of tension and a cystic structure in the left lower zone (Fig. 1).

A chest drain was inserted and a repeat chest X-ray was taken. The left lung had re-expanded but there was an opacity in the left costophrenic angle (Fig. 2).

Clinically the patient improved and the chest drain was removed. Within 36 hours of removal the patient became symptomatic again and the chest X-ray was repeated. The pneumothorax had recurred and the left costophrenic angle opacity was still present (Fig. 3).

A contrast-enhanced CT of the thorax was then performed and revealed a moderately sized left-sided pneumothorax and a well-defined, thick-walled air-filled structure arising from the left lower lobe and adherent to the parietal pleura (Fig. 4 a, b).

Discussion

Background:
Bronchogenic cysts are a congenital abnormality resulting from abnormal development of the tracheobronchial tube, they are part of the family of foregut duplication cysts, enteric cysts and neuroenteric cysts. Cysts are most commonly located in the lung parenchyma or mediastinum and if they communicate with the bronchial tree they will be air filled or contain an air-fluid level. Their location depends on the embryological stage of development at which the anomaly occurs. Cysts that arise later are more peripheral [1].

Clinical perspective:
Previously thought to be asymptomatic and innocent anomalies, recent studies have reported symptoms and complications from bronchogenic cysts and advise surgical excision even in cases without symptoms [2, 3, 4]. Complications from bronchogenic cysts are not uncommon (45%) [5] and include compression of adjacent structures, infection, haemoptysis and not uncommonly pneumothorax as in this case.

Imaging Perspective:
In this case, after multi-disciplinary team discussion it was decided that excision was the best option to avoid repeated pneumothoraces and obtain histological diagnosis. A video-assisted thorascopic excision was performed with no complication. Histology revealed epithelial cells entirely consistent with a bronchogenic cyst.
Appearances on imaging vary depending on the contents of the cyst whether it be fluid, air or a combination of both. CT imaging findings are characteristically of a well-circumscribed round or ovoid solitary lesion with uniform fluid attenuation on CT [7] although the attenuation value can vary with the amount of proteinaceous content. With the administration of IV contrast a non-enhancing or minimally enhancing thin wall is typically seen and the wall can calcify. Thick enhancing walls, septations, solid components and internal calcifications are not typically demonstrated [8].
A definitive diagnosis of a bronchogenic cyst is made when respiratory epithelium is histologically present.

Outcome:
Bronchogenic cysts are benign abnormalities and usually do not recur after excision. The prognosis after excision is excellent although incomplete excision can lead to recurrence and in some patients with pulmonary lesions lobectomy may be necessary [6]. This patient made a full recovery and was discharged by the cardiothoracic team.

Differential Diagnosis List

Final Diagnosis

Recurrent pneumothorax secondary to a ruptured bronchogenic cyst.

URL:	https://www.eurorad.org/case/11624
DOI:	10.1594/EURORAD/CASE.11624
ISSN:	1563-4086