Images in Interventional Pulmonology
Tracheal diverticulosis is a benign condition characterized by single or multiple tracheal wall invaginations mostly found incidentally on postmortem examinations. These are usually recognized incidentally on thoracic computed tomography (CT) as right paratracheal air collections. The condition is mostly asymptomatic; however, in symptomatic patients, a number of symptoms usually pertaining to the upper airway have been described. Management is usually conservative in asymptomatic patients or those with minimal symptoms. Surgical removal of the diverticulae may be required in symptomatic patients.
A 50-year-old male patient presented with history of cough for the past 2 months. Cough was associated with mucoid expectoration, more during early morning hours. Symptoms used to improve by evening. There was no history of fever, wheezing, hemoptysis, chest pain, shortness of breath, leg swelling, loss of weight or appetite, and associated nasal symptoms. Patient was a temple priest and had been a lifetime nonsmoker with no significant occupational exposure. There was no past history of asthma. He had history of chronic cough 10 years ago, subsequently was diagnosed as pulmonary tuberculosis which was successfully cured with 6 months’ worth of antitubercular treatment and patient remained asymptomatic thereafter. There were no other associated comorbid illnesses. General physical examination was unremarkable. Examination of the respiratory system revealed no abnormal findings. Routine blood investigations, spirometry, 12-lead ECG, and chest radiograph were normal. Three sputum smear examinations for acid fast bacilli and mycobacterial cultures were also negative.
As a part of evaluation of persistent cough, multidetector CT (MDCT) examination of the thorax with multiplanar reconstruction was performed. MDCT demonstrated multiple air-filled structures in the region of the right posterior wall of the upper trachea (Fig. 1A). No calcification or wall thickening was seen in the air-filled structures. No connection was noted between them and the trachea on axial images (Fig. 1D). On reconstruction images (Figs. 1B, C), the air collections appeared as outpouchings stacked over each other, arising from the posterior tracheal wall. There was no lung parenchymal abnormality, mediastinal lymph nodal enlargement, or pleural/pericardial effusion. Flexible bronchoscopy was performed. As soon as the flexible bronchoscope was advanced beyond the vocal cords, bubbling and excessive mucoid secretions were noted in the upper trachea. Upon clearing of the mucoid secretions with bronchoscopic suction, multiple wide-mouthed invaginations (diverticulae) were noted in the posterior wall of the upper trachea on the right side (Fig. A and Supplemental video, Supplemental Digital Content 1, http://links.lww.com/LBR/A111), confirming the diagnosis of tracheal diverticulosis. The orifices of the diverticulae allowed easy insertion of flexible bronchoscope into the diverticulum pouches (Supplemental video, Supplemental Digital Content 1, http://links.lww.com/LBR/A111) Patient was informed regarding the chronic and benign nature of the underlying clinical condition. Conservative medical management was initiated with mucolytic and antihistaminic medication for 2 weeks. Chest physiotherapy was also advised to aid in expulsion of secretions. The patient improved and continues to be asymptomatic.
Tracheal diverticula mostly occur on the right side and the proposed reason for same is lack of support to the right posterior tracheal wall due to the left posterior location of esophagus.
It is classified into the congenital or acquired types based on the location and histogenesis.1 Congenital type is relatively small and narrow-mouthed and the usual location is on the right side approximately 4 to 5 cm below the true vocal cords. It may occur in association with other congenital tracheobronchial anomalies. It is proposed to arise from defective endodermal differentiation during development of the membranous posterior trachea wall or from defective tracheal cartilage development. The histology of congenital tracheal diverticulum is similar to the normal tracheal wall.2,3
Our patient fitted into the acquired variety (wide-mouthed and larger in size), which is proposed to originate as a result of conditions leading to increased tracheal intraluminal pressure which leads to herniation of the mucous membrane usually through the weaker posterior membranous trachea (long-standing chronic cough in the past in our patient).3 Acquired diverticula can occur at any level and histologically, its wall lacks mucous glands, smooth muscle, and cartilage.2
Although usually asymptomatic, diverticulae can act as secretion reservoirs, leading to respiratory symptoms like cough, expectoration, or recurrent chest infections.2 Unusual symptoms at time of presentation which have been rarely described include dysphagia, dysphonia, painful neck mass, choking sensation, etc. Difficulty in mechanical ventilation and accidental perforation of a tracheal diverticulum following endotracheal intubation (leading to pneumomediastinum) have also been described as rare complications.1 Serious complications are unusual unlike the diverticulosis of the gastrointestinal tract. Management is usually conservative with antibiotics and mucolytics; however, surgery may be required in patients in whom conservative management is unsuccessful.4 Surgery is preferred in symptomatic young patients and a conservative approach is preferred in the elderly patients with associated comorbidities. Surgery can be accomplished in most of the cases by using a lateral cervical approach without the need for thoracotomy. Endoscopic cauterization with laser or electrocoagulation has also been described as a management modality.1 Radiologic differential diagnoses of paratracheal air collections include congenital tracheal diverticula, tracheoesophageal fistulas, persistence of the tracheal end of a repaired tracheoesophageal fistula, laryngocoele, pharyngeal diverticulum, esophageal diverticula, suppurative tracts from mediastinitis, apical lung hernia, and apical lung blebs which can be excluded by performing a flexible bronchoscopic examination. Tracheal diverticulae have also been reported to occur with Mounier-Kuhn syndrome (tracheobronchomegaly), which was not seen in our patient.5 Patients with multiple tracheal diverticulosis have been previously described in the literature.6
MDCT has been proposed as a very useful modality in the evaluation of these abnormalities as it can detect and delineate finer characteristics like the diverticulum neck and the presence or absence of cartilage in the wall. The same is possible due to the thin slice thickness, greater spatial resolution, and the ability to reconstruct the images in 3 dimension.3 Virtual bronchoscopy images can also be obtained additionally.
During flexible bronchoscopic examination in our patient (Supplemental video, Supplemental Digital Content 1, http://links.lww.com/LBR/A111), we did not observe any cyclical shrinking/expansion of these diverticulae during expiration/inspiration as has been suggested by some authors previously.7,8 In clinical practice, it is not unusual to have patients in whom all preliminary investigations for evaluation of cough are normal and frequently managed as asthma, often with no improvement. In our opinion, it is possible that this condition might be an underrecognized because of recurrent cough which can evade early diagnosis. Knowledge of this clinical entity is important as it can avoid unnecessary and often inappropriate clinical investigations. It is likely that with greater use of advanced thoracic imaging techniques, this entity will be diagnosed more frequently.
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tracheal diseases; diverticulum; bronchoscopy; cough; tracheal diverticulum; posterior tracheal diverticulosis
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