Radiology Cases in Pediatric Emergency Medicine Volume 6, Case 17 Meta Lee, MD

A 10 month old male comes to the ED with a chief complaint of wheezing and coughing for one day. He has just flown in from the Marshall Islands with his parents and an interpreter, who are not available at this time. He has no fever, vomiting or diarrhea. Despite the language barrier you are able to elicit that the patient has had similar coughing and wheezing episodes in the past.

VS T37.1 (tympanic), P120, R58, oxygen saturation 100% (room air). He is noted to be in mild respiratory distress with audible wheezes, mild-moderate retractions, moist expiratory rhonchi and crackles diffusely.

He is given an albuterol nebulizer treatment with marked improvement in symptoms. His respiratory rate decreases, his retractions resolve, his aeration improves and his breath sounds clear except for a slight decrease in aeration on the left. His mother communicates that he is to see a doctor the following day, and you decide to discharge the patient on albuterol syrup with instructions to follow-up with this physician in the morning.

The next day he comes to the clinic with his interpreter, who has a copy of his medical records from the Marshall Islands. He has had a history of recurrent episodes of wheezing and cough with respiratory distress for which he has been hospitalized at 1, 3 and 4 months of age. His mother indicates that he is doing much better since his ED visit last night. A chest radiograph is ordered.

The PA view demonstrates decreased pulmonary vascularity and hyperlucency of the left lung. His right lung demonstrates increased pulmonary vascularity. The lateral view demonstrates a mass effect posterior to the lower portion of the trachea, which compresses and bows the trachea anteriorly with considerable narrowing of the inferior portion of the trachea and left main bronchus. These findings are suspicious for a large mediastinal mass which is compressing the lower trachea and mainstem bronchus causing obstructive emphysema of the left lung and decreased perfusion of this lung. A barium esophagram is ordered.

Barium is hand injected into the proximal esophagus through a nasogastric tube. The esophagus is displaced laterally as seen on the AP view. The lateral view demonstrates the mass located between the trachea (the tracheal air column is compressed and displaced anteriorly) and the barium filled esophagus (which is displaced posteriorly). A CT scan of the chest is ordered.

There is a 4.5 x 4.5 x 2.5 cm cystic mass posterior to the trachea and the mainstem bronchi. The mass causes marked narrowing of the left main bronchus. The esophagus is displaced to the patient's right by the mass with flattening of the esophageal lumen. This mass is most likely a mediastinal bronchogenic cyst. An esophageal duplication cyst could have a similar appearance.

The patient underwent surgical excision of the mediastinal mass via thoracotomy without complications. Pathology confirmed the mass to be a bronchogenic cyst.

Bronchogenic cysts represent 10-20% of congenital cystic diseases of the lung, and account for approximately 10% of mediastinal masses. These cysts are the result of ectopic budding of the tracheobronchial tree during embryologic development from the primitive foregut. Histologically, these cysts are composed of tissue normally found in the trachea and bronchi (mucous glands, smooth muscle, elastic tissue and usually cartilage). Fluid found within is mucoid and clear or white, unless hemorrhage has occurred, in which case the contents are thick and brown. Calcium crystals may also be seen. Because these cysts form before the development of alveoli, there is no gas exchange potential, even if communication exists. Bronchogenic cysts can be classified by location: paratracheal, carinal, paraesophageal, hilar and miscellaneous. The majority of bronchogenic cysts are either attached to the tracheobronchial tree by a stalk of fibrous tissue or are embedded in the wall of the trachea or bronchus. Less frequently, there may be communication with the respiratory tract, resulting in progressive dilatation with air, resulting in atelectasis, recurrent infection and mediastinal shift.

Clinically, the majority of bronchogenic cysts are symptomatic and occur in infancy or early childhood. Respiratory distress is the most common presentation in pediatric patients, manifested by recurring episodes of cough, stridor, wheezing and retractions. In later childhood or adulthood, bronchogenic cysts are more commonly asymptomatic, with symptoms eventually developing due to increasing size of the cyst. Chest pain, cough and dyspnea are the most common complaints in adults. Persistent or recurrent pneumonia, abscess or empyema can occur at any age as a result of impaired clearance of secretions past the cyst, or infection, or rupture of the cyst itself. Diagnostically, bronchogenic cysts can be identified on plain chest radiographs in up to two thirds of cases in any age group. The radiographic appearance depends on whether the cyst is air filled, fluid filled, or air and fluid filled. An air filled cyst has the appearance of a pneumatocele. Completely fluid filled cysts cannot be discriminated from solid masses on plain film. The presence of air-fluid levels on erect or decubitus films imply tracheobronchial communication and active infection, which can be difficult to distinguish from a lung abscess. Bronchogenic cysts may not be visible on chest radiographs due to surrounding mediastinal structures and inflammation. Hyperinflation, pneumonitis, atelectasis, mediastinal deviation, or abnormal separation of the trachea and esophagus may impede the radiographic visibility of a bronchogenic cyst. Computed tomography helps to better define the cyst in terms of fluid content, wall thickness, solitary or multiple nature, location and other findings.

Treatment options for bronchogenic cysts include observation, resection and aspiration. All symptomatic or enlarging cysts should be resected. Infected cysts should be removed once tissue levels of broad-spectrum antibiotics have been established. In poor surgical candidates, aspiration of a cyst can be done to confirm a benign diagnosis. Instillation of a sclerosing agent is another therapeutic option. Asymptomatic simple cysts, if observed, have the potential to grow and can result in higher rates of perioperative complications once becoming symptomatic. There is also a rare association of bronchogenic cysts with rhabdomyosarcoma.