What is Congenital Pulmonary Airway Malformation (CPAM)?
A CPAM (formerly referred to as a CCAM or Congenital Cystic Adenomatoid Malformation) is a cystic mass which forms in the lung tissue of a fetus. The mass is usually located in one lung, and it does not function as normal lung tissue. Its cause is unknown, and it is not related to anything the mother did or did not do during the pregnancy. We suspect that it is caused by a genetic problem. The mass is made of somewhat immature, fast-growing lung cells. The size of the CPAM is often such that a normal lung cannot grow well.
How is CPAM diagnosed?
CPAMs are detected during a routine prenatal ultrasound. A CPAM is made of somewhat immature, fast-growing lung cells that appear on the ultrasound as a bright mass in the area of the chest where only lung tissue should be seen. The size and location of the mass may impact normal lung development. It may also cause the heart to shift to the opposite side of the chest or push downward on the baby’s diaphragm.
At the SSM Health St. Louis Fetal Care Institute the diagnosis can be confirmed with a fetal magnetic resonance imaging (MRI) exam which will also document the size and location of the CPAM. Another test that may be recommended is a fetal echocardiogram (echo). This is an ultrasound of the heart performed by a pediatric cardiologist. This test is recommended to rule out structural heart defects and assess heart function.
How does CPAM affect my baby?
The vast majority of babies do well and have normal development and lung function. During the pregnancy, the cyst often grows with the fetus and appears quite large; however, the growth usually starts to slow down in the second trimester. Since the fetus and the remaining normal lung continue to grow rapidly, the mass appears to shrink over the pregnancy. Sometimes, the mass becomes very small and even undetectable by ultrasound before birth. It is always there, but studies will have to be done after birth to find the mass. In all these cases, the outlook for a normal life is excellent.
In a small number of fetuses, the CPAM may grow so rapidly that it becomes life-threatening before birth. This usually happens between 18 and 26 weeks gestation. The large size of the mass causes compression of the heart and heart failure. Compression of the lungs can also cause the lungs to be too small for survival. In these cases, either fetal surgery or early delivery may need to be performed depending on how far the pregnancy has progressed.
How is CPAM managed during pregnancy?
During the initial ultrasound, we will measure the volume of the CPAM (or CCAM) relative to the size of the fetus. This ratio is called the CPAM volume ratio, or CVR. For every fetus with a CPAM, we start by measuring the CVR every week. By comparing the CVR measurements, we can determine how fast the the mass is growing and whether it will become life-threatening. If the CVR remains small (less than 1.0) after 28 weeks, then the ultrasound examinations can be performed every three to four weeks until delivery.
If the CPAM pushes the heart out of the normal position, then a second MRI may be performed around 32-34 weeks of pregnancy. The lung volume will be calculated and the information will be used to determine whether your baby should be delivered at SSM Health St. Mary’s Hospital - St. Louis or SSM Cardinal Glennon Children’s Hospital, both of which offer advanced breathing machines and additional therapies for critically ill newborns.
Babies with very large, rapidly growing CPAMs will have a high CVR, usually above 1.0. In this setting, we follow your baby very closely to determine if the heart function begins to decline. Usually, ultrasound exams need to be performed twice a week and repeated echos may also be performed.
If signs of heart failure develop, or the CVR rises to 1.6 or higher, then fetal intervention may be required. Oftentimes, prenatal steroids are the first step in the intervention. These steroids are given to the pregnant mother and may work to slow or stop growth of the mass. If the steroids do not stop the growth of the CPAM, then open fetal surgery to remove the mass can be a life-saving option for the baby. If it has a dominant cyst of fluid then a needle can be used to drain the fluid and relieve the compression on the heart. When the CPAM is a solid mass, then open fetal surgery is necessary to remove the mass. If the baby has reached 32 weeks in pregnancy, then early delivery may be used instead of fetal surgery.
How is CPAM treated after delivery?
If fetal intervention is not necessary the infant will be evaluated and treated after delivery. Babies with a relatively small CPAM can be born without any apparent complications. These babies typically go home and are followed as an outpatient in 2 to 4 weeks. The pediatric team manages what to do with the CPAM. Often they recommend surgical removal to prevent future infection and the uncommon, possible malignancy. This is done though an operation in the chest and the part or lobe of the lung that contains the mass is removed.
Babies with a moderately large CPAM may have some difficulty breathing after birth. Usually, these babies breathe very quickly and sometimes they require oxygen. Eating is difficult when breathing fast. These babies need to be in a neonatal intensive care unit (NICU) for stabilization and surgery is performed to remove the CPAM and to allow for the remaining normal lung to function optimally. The baby will remain in the NICU until breathing and eating improve.
Rarely, a CPAM is so large that we anticipate the baby will have problems breathing right at birth. We try to predict this based on the size of the mass and lungs by MRI, and the degree that the heart has been pushed out of the way. To avoid a crisis in the baby’s breathing at birth, we recommend that a special delivery method be used. When a baby is delivered using an Ex Utero Intrapartum Treatment (EXIT) procedure, the placenta and umbilical cord are maintained while we evaluate the baby’s lung function. If the baby breathes well, then the baby can be completely delivered and we can plan for removal of the CPAM later. If the baby’s breathing is compromised, then the mass needs to be removed immediately. The chest operation is performed while the mother’s placenta supports the baby. When the operation is finished, the cord is cut and the baby can breathe better without the compression of the mass.
What will happen after surgery?
The post-operative course varies depending on when the surgery is done, the size of the mass, and how much lung was removed. If the CPAM (formerly known as CCAM) is removed during the neonatal period, then commonly a breathing tube and intravenous line is needed. The baby may also have a tube in the chest to drain any fluid and help expand the lung into the chest space. The baby will not be able to eat until his or her condition has stabilized but nourishment will be given through the intravenous fluids.
The baby will go home when he or she can breathe sufficiently and eat enough to maintain and gain weight. The average stay for the newborn can range from 2-3 days for small CPAMs to 4-8 weeks for much larger ones. The long-term outcome for infants who have the cyst removed is excellent. These children usually have no limitations on their activities and have no increased risk for respiratory complications.