Congenital pulmonary airway malformation (CPAM), also commonly called congenital cystic adenomatoid malformation (CCAM), of the lung is a multicystic mass of abnormally developed lung tissue. Rarely a CPAM can become relatively large and act as a space-occupying lesion within the fetal chest. This can result in underdevelopment of the lung tissue and lethal pulmonary hypoplasia, as well as compression of cardiovascular structures and eventual fetal hydrops (heart failure) and death.
CPAM is an overgrowth of terminal respiratory bronchioles that form cysts of various diameters. The CPAM can be detected prenatally by ultrasound. The chest mass may be mainly cystic, mainly solid, or cystic and solid in appearance. Type I CPAM (macrocystic) is comprised of cysts that measure between 2 and 10 centimeters in diameter. Type II CCAM (macrocystic with microcystic component) have cysts less than 2 centimeters is diameter. Type III CPAM (microcystic) have cysts that measure less than 0.5 centimeters in diameter, and appear solid and echogenic on prenatal ultrasound.
Fetuses with CPAM’s should be monitored closely during the pregnancy for possible heart failure. If fetal hydrops develops, the baby may be treated while in the womb using a variety of treatment options. In cases of Type I CPAM, thoracoamniotic shunting can be performed. A thoracoamniotic shunt is a tube that is placed into the chest so that one end is in the cystic chest mass and the other end is protruding out of the chest and into the amniotic cavity. This tube allows for drainage of the cystic fluid within the CPAM into the amniotic fluid. By decompressing the CPAM, the lungs can develop more normally and the heart can function better. In Type II and Type III CPAM’s, treatment to the fetus can be given via sclerotherapy. Preliminary results have shown that hydrops fetalis can resolve within three to four weeks after sclerotherapy of a microcystic CPAM.
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