BRONCHOGENIC CYSTS

Bronchogenic cysts result from abnormal budding of the ventral foregut diverticulum between 26 and 40 days of embryogenesis (this is the most active period for tracheal and bronchial development) (1). Respiratory epithelium lines the cyst and the walls contain mucous glands, cartilage, elastic tissue and smooth muscle (1-9).

LOCATION

1. Mediastinum Bronchogenic Cyst
• Pericardial (52%), paratracheal (19%), esophageal wall (14%), retrocardiac (9%).
• Usually on the right side, single and centrally located.
• May communicate with tracheal lumen.
• Males = females.
2. Intrapulmonary Bronchogenic Cyst
• Centrally within the lung (lower lobe:upper lobe = 2:1).
• Rarely below the diaphragm.
• Males more common than females.
• Does not usually communicate with the tracheobronchial tree.
• Well circumscribed and hyperechogenic on ultrasound.
• Can cause more diffuse pulmonary hyperechogenicity.
3. Ectopic intra-abdominal bronchogenic cyst has been described (10). Other ectopic locations include the cervical and retroperitoneal regions.

ULTRASOUND (2-4)

• Well defined unilocular mass within the mediastinum or lung parenchyma
• Cystic in nature and adjacent to the mediastinum.
• Usually single.
• mm to over 5cm and may adhere to the bronchial or bronchiolar wall, or communicate via a pedicle.
• No mediastinal shift, polyhydramnios or fetal hydrops is present.
• Compression of the adjacent lung (large cysts) with subsequent pulmonary hypoplasia.
• Compression of a mainstem bronchus or esophagus has been described (5)
• Compression of the intrathoracic great vessels and lymphatics producing ascites and nonimmune hydrops may occur (7).
• The cyst usually increases in size with advancing gestation.

ASSOCIATED ANOMALIES

• Usually isolated.
• Reece and co-workers (6) reported on two cases with severe associated anomalies, however this is the exception rather than the rule.

REFERENCES

1. Inselman LS, Mellins RB. Growth and development of the lung. J Pediatr 1981;98:1-15.
2. Avni EF, Vandereslt A, Van Gansbeke D et.al. Antenatal diagnosis of pulmonary tumors: Report of two cases. Pediatr Radiol 1986;16:190-192.
3. Albright EB, Crane JP, Shakelford GD. Prenatal diagnosis of a bronchogenic cyst. J Ultrasound Med 1988;7:91-95.
4. Reece EA, Lockwood CJ, Rizzo N et.al. Intrinsic intrathoracic malformations of the fetus: sonographic and clinical presentation. Obstet Gynecol 1987;70:627-632.
5. Young G, L'Heureaux, Kruekeberg JT et.al. Mediastinal bronchogenic cyst: Prenatal sonographic diagnosis. AJR 1989;152:125-127.
6. Reece EA, Lockwood CJ, Rizzo N et.al. Intrinsic intrathoracic malformations of the fetus: Sonographic and clinical presentation. Obstet Gynecol 1987;70:627-632.
7. O'Mara CS, Baker RR, Jeyasingham K. Pulmonary sequestration. Surg Obstet Gynecol 1878;147:609.
8. Rahmani MR, Filler RM, Shuckett B. Bronchogenic cyst occurring in the antenatal period. J Ultrasound Med 1995;14:971-973. 
9. St Georges R, Deslauriers J, Duranceau A. Clinical spectrum of bronchogenic cysts of the mediastinum and lungs in the adult. Ann Thoracic Surg 1991;52:6-13.
10. Bagolan P, Bilancioni E, Nahom A et.al. Prenatal diagnosis of a bronchogenic cyst in an unusual site. Ultrasound Obstet Gynecol 2000;15:66-68