Congenital Pulmonary Airway Malformation

Abstract

Congenital pulmonary airway malformations (CPAM) refer to an unusual lesion of the pulmonary airways which combines features of hamartoma malformation and dysplastic proliferation. CPAM includes cystic pulmonary airway malformations, bronchopulmonary sequestration, bronchogenic cysts, hybrid lesions and lobar/segmental emphysema causing respiratory distress in 20-40% of affected babies in the postnatal period. The remaining cases continue asymptomatic or develop symptoms later in life such as chest infections. Most CPAM can be detected on the 20-week antenatal ultrasound increasing the diagnostic yield if MRI is utilized. Children with symptoms early in life are managed with surgery. The management of asymptomatic CPAM is a source of controversy in the literature. CPAM is classified 0 to IV. Type 0 is very rare described as acinar aplasia or agenesis and incompatible with life. Type I the most common is primarily macrocystic with large single or multiple cysts several centimeters in size. Type II is microcystic and associated with other anomalies. Type III appears more solid or with very small cysts similar to immature lungs without bronchi. Type IV originates from the acinus and present with small cysts on the periphery of the lung lobes. Once a cystic lesion is detected in antenatal ultrasound, the location, volume, size, macrocystic or microcystic classification and blood supply should be evaluated. CPAM volume to head circumference ratio (CVR) greater than 1.6 results in fetal demise in about 80% of cases without fetal intervention. CVR < 1.6 will often not continue to grow past the 28th week of gestation. The reasons used to remove asymptomatic lesions in the first year of life include the rate of empyema, abscess, recurrent pneumonia, air leak, pneumothorax and malignancy. Almost 25% of asymptomatic children show histologic evidence of infection. CPAM have a long-term risk of malignancy. Multiple courses of antenatal betamethasone for high-risk fetal CPAM often results in favorable short-term outcomes without the need for open fetal resection.