Characteristics And Diagnosis Of Tracheal Diverticulum

Tracheal diverticulum is a rarely encountered congenital or acquired entity of the posterior tracheal wall. Most cases are asymptomatic, typically being diagnosed postmortem; but when symptoms are present they are usually nonspecific. Most of the patients encounter respiratory symptoms because the diverticula usually act as reservoirs for respiratory secretions. Due to this secretions accumulation the patient usually presents with chronic cough and recurrent tracheobronchitis, and less common the patient can present with dyspnea, dysphagia, dysphonia, recurrent nerve paralysis, cervical neck swelling, hematemesis, and hemoptysis.

Tracheal diverticulum can also be associated with abnormal pulmonary function and obstructive lung disease, mainly emphysema.

Imaging techniques are the most diagnostic tool because the point of communication with the trachea is difficult to detect with bronchoscopy. Overall prevalence has been estimated from cadaveric studies to be approximately 1%, whereas more recent radiologic studies suggest a higher prevalence of 2% to 3.7%. We herein describe a patient with chronic cough and chest pain who was found to have tracheal diverticulum.

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A 56 year old woman with history of recurrent bronchitis requiring antibiotic presented to the emergency department for chest pain. She denied any history of smoking or any occupational fume exposure. Chest x-ray results didn’t show any airspace disease. Because of recurrent chest pain and infection, a computed tomography angiogram of the chest was done to rule out pulmonary embolism, which demonstrates a multiseptated tracheal diverticulum measuring 2 x 1.9 x 1.9 cm. There was no wall thickening or calcifications. The presence of a narrow stalk connecting the lesion with the posterior wall of the trachea was critical in establishing the diagnosis of a tracheal diverticulum, although we did not perform a histological examination, the location of the tracheal diverticulum was that most often reported in clinical reports.

Patient was discharged home on antibiotics to follow up with outpatient pulmonary clinic.DiscussionTracheal diverticulum is a benign and very rare entity characterized by single or multiple invaginations of the tracheal wall.

Tracheal diverticulum is usually found post-mortem and the frequency of the tracheal diverticulum in some autopsy series has been estimated to 1%. In most cases tracheal diverticulum is located at the right posterior-lateral side of the trachea and it appears to have one or multiple connections with this structure. Tracheal diverticula can be classified as either congenital or acquired diverticulum. It also described as tracheogenic cysts (when the wall of the diverticulum include muscle and cartilage and generated from an embryonic origin), on the other hand tracheoceles, and diverticula (both lacking a muscular frame). The latter two are differentiated by number or by size, with tracheoceles being of one single formation or else larger than 2 cm and diverticula being multiple formations or smaller than 2 cm. Congenital tracheal diverticulum is more common in men than in women. It appears 4-5 cm below the vocal cords or above the carina, generally in the right lateral part of the trachea. It is usually small and the communication with the trachea is narrow. It is thought to represent a vestigial supernumerary lung or malformed branch of the trachea. Others believe that it arises from a defect in endodermal differentiation during development of the membranous posterior tracheal wall, or else from a defect in the development of the tracheal cartilage during the sixth week of fetal life. They occasionally accompany other congenital malformations such as tracheoesophageal fistula. They resemble complete tracheal structures including cartilage and smooth muscle in addition to the respiratory epithelium and mucus glands. Similarly, bronchogenic cysts of the mediastinum also harbor these tissue elements. However, although they tend to arise on the right side of the trachea similar to the tracheal diverticula, they have no communication with the lumen of the trachea.

Acquired tracheal diverticula may appear at any level, though they are more common in the posterolateral region. Acquired tracheal diverticula are larger than congenital tracheal diverticula and have a wider connecting opening. They originate as the result of increased intraluminal pressure caused by chronic cough or obstructive lung disease with emphysema that results in herniation of the mucous membrane through a weak point in the tracheal wall combined.The wall in acquired tracheal diverticula, unlike in congenital diverticula, is formed solely of respiratory epithelia and lacks any cartilaginous or smooth muscular elements. Acquired tracheal diverticula may be single or multiple. Mounier-Kuhn syndrome described as multiple tracheal diverticulum, marked dilatation of the trachea and bilateral main bronchi, bronchiectasis and recurrent lower respiratory tract infections.

Most cases of tracheal diverticula, whether congenital or acquired are asymptomatic and incidentally detected. In addition to increased risk of infection due to accumulation of secretions, the disorder may be accompanied by hemoptysis, dyspnea, dysphagia, and repeated episodes of tracheobronchitis or stridor. Tracheal diverticula may also occasionally cause dysphonia due to compression of the vocal cords. Finally tracheal diverticulum can be iatrogenic due to traumatic intubation or pneumomediastinum.

The differential diagnosis includes laryngocele, pharyngocele, Zenker’s diverticulum, apical lung hernia, and bullae. Pharyngocele and Zenker’s diverticulum can be detected by barium swallow. Apical hernia and apical bullae of the lung can be identified on CT, and laryngocele can be localized as the dilated saccule of the laryngeal ventricle. Some cases of tracheal diverticula may be misdiagnosed as intrathyroid tumors, especially when they reach the proximal trachea.Computed tomography is the proper imaging method for the study of tracheal diverticulum. It can demonstrate the connection between the diverticulum and the tracheal lumen. Although bronchoscopy can establish the diagnosis, diverticula with a narrow opening or just a fibrous connection with the trachea can be bronchoscopically missed.The treatment approach varies according to the age, clinical presentation, and the presence of comorbidities. Surgical resection is typically reserved for younger, highly symptomatic patients, whereas older patients, especially those with comorbidities, are treated conservatively using antibiotics, mucolytics agents and physiotherapy.

Conclusion

Tracheal diverticulum is a very rare entity and is frequently an incidental finding on post mortem. The radiographic appearance can mimic other causes of paratracheal air collections and cavities. CT or fiberoptic bronchoscopy are the most appropriate Diagnostic techniques. Treatment should be tailored according to patient symptoms and age.