Teaching Case

Female, 56 years old, longtime smoker (10 cigarettes a day for 43 years), complaining of daily chronic cough and dyspnea for about 1 year, worsening in the last 4 months. She also reported frequent episodes of rhinitis. She denies other comorbidities or medications for continuous use.

The chest computer tomography (CT), performed with intravenous contrast, demonstrated signs of chronic obstructive pulmonary disease and centrilobular emphysema, predominant in pulmonary apexes. The cardiovascular system was normal. Another finding was a cystic, lobulated image, with a gaseous content, adjacent to the right posterolateral aspect of the upper third of the trachea (Figures 1 to 3). This image showed little communication with the trachea in its inferior aspect (Fig. 4), and the diagnosis of incidental tracheal diverticulum was considered.
A follow-up with the pulmonologist was required for the patient for a conservative treatment.

Tracheal diverticula (TD) were first described by Rokitansky in 1838 and are small, single or multiple tracheal evaginations, full of air and communicating with the trachea, which are usually found in incidental CT scans of the neck, cervical spine or chest [1-8]. Its estimated prevalence was around 1% in the series of autopsies performed by MacKinnon [9], but with the advent of multidetector computed tomography, some studies have shown a higher incidence, ranging from 2.4 - 8.1 * [3, 4, 6,10,11]. However, until today there are few cases of TD reported. It can be confused with a laryngocele, that is located more superiorly, laterally to the false vocal cord, and it has higher incidence [2]. Other differential diagnoses include pharyngoceles, Zenker's diverticula, apical pulmonary hernias, pneumomediastinum or bullae [1,2,5,10,12].
TDs are classified as congenital or acquired, the former being less common and generally of smaller dimensions [2,7,8). In a histological evaluation, the congenital TDs are composed of respiratory epithelium, smooth muscle and cartilage, and those acquired are formed from respiratory epithelium only [1,2,4,5,7,8,12]. The aetiology is still uncertain, but it is believed that acquired cases, such as the one described here, may be produced by hernias of the mucosa through a weak spot, as a result of increased intraluminal pressure [1-7,11, 12]. They occur more commonly in the right posterolateral aspect because the cartilaginous rings are deficient and there is no oesophagus for support [1-3, 6-8,10,12]. Most cases are asymptomatic, however in rare occurrences they can be linked to recurring infections [4,5,11,12], chronic cough [1-4,9,12] recurrent laryngeal nerve palsy and hoarseness [2-5,7 , 11,12], difficulty in intubation [2-5,13], hemoptysis, dyspnoea and dysphagia [2,4,5,11,12].
The exam of choice to detect TD is CT, which provides the location, origin and size of the lesion, with excellent precision, thus helping to distinguish between congenital and acquired [2,4,11,12]. Techniques such as three-dimensional reconstruction also contribute to the morphological diagnosis of this condition. Bronchoscopy is useful to confirm the diagnosis, although there are cases where a connection was not visible, for example, in diverticula with a very narrow opening or those connected to the trachea by only one fibrous tract [2,5].
Most cases of TD do not need treatment, except when they are symptomatic or large. Several approaches in these cases have been described, including surgical resection and endoscopic cauterization [2,4,12].
* Statistics included all paratracheal air cysts: tracheal diverticula, tracheoceles, lymphoepithelial and bronchogenic cysts.