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.
     Exam:  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.

View his chest radiographs.
PA view.


Lateral view.


     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.

View esophagram.
AP view.


Lateral view.


     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.

View CT scan.


     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.

Discussion
     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. 

References
     1.  Coran A, Drongowski R.  Congenital Cystic 
Disease of the Tracheobronchial Tree in Infants and 
Children - Experience with 44 Consecutive Cases.  
Archives of Surgery 1994;129:521-527.
     2.  Decamp M.  Congenital Cysts of the 
Mediastinum:  Bronchopulmonary Foregut Anomalies.  
In:   Fishman A (ed).  Pulmonary Diseases and 
Disorders, third edition. New York, NY, McGraw-Hill 
Companies, Inc., 1998, pp. 1499-1506.
     3.  Freundlich I, Bragg D.  Cysts and Cavities of the 
Lung.  In:  Freundlich I, Bragg D (eds).  A Radiographic 
Approach to Diseases of the Chest.  Baltimore, MD, 
Williams and Wilkins, 1992, pp. 93-99.
     4.  Haddon M, Bowen A.  Bronchopulmonary and 
Neurenteric Forms of Foregut Anomalies - Imaging for 
Diagnosis and Management.  Radiology Clinics of North 
America 1991;29(2):241-251.
     5.  Lierl M.  Congenital Abnormalities.  In:  Hilman B 
(ed).  Pediatric Respiratory Disease: Diagnosis and 
Treatment.  Philadelphia, PA, W.B. Saunders 
Company, 1993, pp. 457-461.