Congenital cystic adenomatoid malformation
Description, Causes and Risk Factors:
Lungs are normally divided into sections called lobes; three on the right and two on the left. A congenital cystic adenomatoid malformation (CCAM) is an abnormality of one or more lobes in which the lobe forms as a fluid-filled sac, called a cyst, which does not function as normal lung tissue. Congenital cystic adenomatoid malformations develop with equal frequency on either side of the lung, but rarely occur on both sides.
Congenital cystic adenomatoid malformation is classified into three types:
Type I lesions account for 50 percent of the postnatal (after birth) cases. These are usually quite large, cystic lesions that are few in number (1 to 4). This type has a very favorable outcome.
- Type II lesions account for 40 percent of the postnatal cases. This type consists of more numerous smaller cysts. This type is more commonly associated with other congenital anomalies, including those of the genitourinary, cardiac, skeletal systems as well as hydrocephalus and diaphragmatic hernia. The prognosis for type II is dependent on the severity of the associated anomalies.
- Type III lesions account for only 10 percent of the postnatal cases. These are usually large, microcystic lesions that cause shifting of the organs normally found in the chest. This means that the windpipe, heart and unaffected lung are shifted and compressed. For this reason, heart function may be less than normal. This can lead to the development of hydrops (abnormal accumulation of fluid in at least two fetal cavities such as in the abdomen, around the heart, or lungs or under the skin). The prognosis for Type III is poor, especially when hydrops is seen.
A Congenital cystic adenomatoid malformation is caused by overgrowth of abnormal lung tissue that may form fluid-filled cysts. The cysts prevent the tissue from functioning as normal lung tissue. The abnormal development occurs in the baby when in the mother's womb. Adenomatoid overgrowth of lung tissue leads to this situation. The reason for abnormal development is still unknown. The incidence of CCAM is approximately 1 in 25,000 pregnancies.
Most CCAMs either shrink or are small enough not to cause a problem. They are almost always benign, although in rare cases, they become cancerous later in life. The cyst also can become infected and cause pneumonia
. For this reason, it's generally recommended to remove Congenital cystic adenomatoid malformations after birth.
The first sign of CCAM is often a pregnant mother who measures too big for her due date because there is too much amniotic fluid. This is due to the Congenital cystic adenomatoid malformation pushing on the heart and esophagus of the fetus, preventing the fetus from swallowing amniotic fluid.
Most infants born with a CCAM have no symptoms at birth, although occasionally an infant may have difficulty breathing and will require oxygen and the use of a machine called a ventilator.
A large Congenital cystic adenomatoid malformation can cause a condition called hydrops — accumulation of fluid in the skin, chest, or abdomen that reflects severe heart failure — as it presses against the heart and makes it work harder to circulate blood. About 10 percent of all fetuses with CCAM develop hydrops. Untreated, a fetus with hydrops and CCAM usually will not survive.
The mass can be so large that it limits lung development and causes pulmonary hypoplasia
, or small lungs. The CCAM can also push on the heart and the esophagus of the fetus, preventing the fetus from swallowing amniotic fluid. This can result in the mother suffering from polyhydramnios, or too much amniotic fluid.
The diagnosis of congenital cystic adenomatoid malformation (CCAM) may have serious implications for the health of the mother. If the fetus develops hydrops, or massive fluid retention, the mother may "mirror" the sick fetus, becoming ill with signs of preeclampsia. Fetal surgery does not cure the preeclamptic state, and mothers must be carefully monitored for signs and symptoms of the maternal mirror syndrome.
Serial ultrasounds are scheduled to monitor the size of the CCAM during gestation and detect any fetal problems. A CCAM-volume-ratio (CVR) will be calculated to help predict problems during pregnancy. The chromosomes are usually normal in babies with CCAM. A fetal echocardiogram is recommended to assess heart structure and function. In select patients with a large CCAM, a fetal MRI may be performed to define the lesion and assess lung volumes.
Prenatal diagnosis provides insight into the in utero evolution of fetal lung lesions such as congenital cystic adenomatoid malformation, bronchopulmonary sequestration and congenital lobar emphysema. Serial sonographic study of fetuses with lung lesions has helped clinicians to define the natural history of these lesions, determine the pathophysiologic features that affect clinical outcome and formulate management plans that are based on prognosis.
Most babies with Congenital cystic adenomatoid malformationare treated with surgery soon after birth or several months later, depending on the severity of the CCAM. A small group of severe cases may be treated before birth with fetal intervention.
Infants with no symptoms at birth can go home after a few days in the hospital and return at 3 months of age for a CT scan. An operation to remove the CCAM may be scheduled after the pediatric surgeon and radiologist review the results. CCAM removal is generally recommended because of the risk of lung infections and cancerous transformation later in life.
In most infants, the operation is done with tiny telescopic instruments though several very small incisions, instead of a single large chest incision. Your baby will stay in the hospital two to three days but probably will be released as soon as he or she is breathing easily, takes formula or breast milk well and is comfortable on pain medication given orally.
Fetal intervention is offered only when there is evidence of heart failure in the fetus. The procedure involves an operation for the mother, like a Caesarean section, in which a fetal surgeon removes the CCAM from the fetus' chest.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.