CONGENITAL LUNG LESIONS?
There are three broad categories
lung lesions: Cystic
adenomatoid malformations (also called CCAM), bronchopulmonary sequestrations (or sequestrations, for short)
cysts. All three types represent the abnormal development
of lung tissue, which may occur during normal fetal development. Why these lesions form
is not really known; how they differ from each other may have
to do with the timing and location of their development.
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In the embryo, the lungs develop
as an outpouching of what will become the esophagus: a "bud" develops, which
elongates to become the trachea, then divides to become the left and
right main stem bronchi. Further division of each bronchus will, like the branches of a growing
tree, form the "tracheobronchial" tree of airways.
At the same time, the lung parenchyma (the actual lung tissue
responsible for exchange of oxygen and gases into and out of
the bloodstream) develops around each of those airway branches.
cyst is nothing more than an airway branch that buds off,
loses all connections with the rest of the tracheobronchial tree, and does not connect
with actual tissue. As a result, a cyst forms, which is lined by the same cells
one finds in the trachea or the bronchi.
A sequestration represents a portion of lung
(with a bronchus
and some lung tissue) that has completely separated from the
rest of the lung. If this separation occurs relatively early
in embryonic life (before the 6th week of pregnancy), this "mini-lung"
is usually fully developed and separate from the rest of the
organ. It also contains its own blood supply: an artery that
is directly connected to the aorta, for example. However, because it is
separate from the rest of the lung, no air goes in or out of
this "extralobar" sequestration.
If the separation from the rest
of the lung occurs later (between the 8th and the 12th week of
pregnancy), it usually remains within the normal lung (but may
still have separate blood vessels). Even though it is not connected
to the rest of the tracheobronchial tree by a normal bronchus, there may be microscopic communications
with the rest of the lung: in this type, the "intralobar" sequestration, some air (and bacteria) may
get trapped in the lesion after birth, which may cause recurrent
The congenital cystic adenomatoid malformation (CCAM)
is less easily explained, but consists of some or all types of
lung and bronchial
cells and structures, arranged in a disorderly fashion. It is
not a tumor, however: the cells themselves are not malignant and do not grow, invade other organs
or spread to other parts of the body; rather, it is a "clumsily
put together" part of lung, that doesn't function properly.
Because a CCAM
tends to develop within the normal lung, microscopic communications
with that lung also place the child at risk for infections, from
trapped air and bacteria.
While the above classification
is helpful, it is not always clear-cut, and many "hybrid" forms exist: lesions that have
characteristics of more than one type. In addition, in up to
50% of sequestrations, part of the otherwise normal
lung tissue is replaced by a CCAM.
Congenital lobar emphysema is one more form of congenital lung lesions, but it is much less
common than the ones mentioned above. In congenital lobar emphysema, or CLE, one of
of a lung may be partially and/or intermittently blocked, causing
accumulation of fluid and distension of the lung tissue connected
to that bronchus.
While the cause of this condition is different, its course and
treatment is remarkably similar to that of the lesions described
Congenital lung lesions are seen in approximately in 1 of
every 3,000 live births. They are most often isolated findings,
not associated with chromosomal or genetic disorders. CCAMs and sequestrations are sometimes seen in fetuses
with a congenital
diaphragmatic hernia, and can be an incidental finding (i.e.,
discovered by chance) in otherwise healthy children or children
with unrelated anomalies.
CAN HAPPEN BEFORE BIRTH?
Most congenital lung lesions do not become visible
until early in the second trimester. They often grow, sometimes
fast, causing the lung on the same side to be compressed. In
addition, the heart may be pushed to the other side, and even
the lung on the other side may be compressed. If the lesion becomes
very large, it may start to affect the well-being of the fetus:
extreme compression of the heart and the large blood vessels
of the chest may impair the heart's function, and this could
lead to hydrops
(heart failure) and death. If compression of organs in the chest
is severe and continues for a long time during pregnancy, the
baby's lungs may not function well at birth (pulmonary hypoplasia).
In most cases, however, growth
of these lesions is limited, and they tend to become smaller
toward the end of the second trimester. In approximately 75%
of the cases, the lesion regresses either partially or completely
by the time the baby is born; not uncommonly, the lesion is not
visible by prenatal ultrasound anymore.
Figure 1: MRI of a lung lesion (arrow: wedge-shaped
lesion, *normal lung)
Of course, premature birth can
affect the outcome, particularly if it occurs as the lesion is
still large and compressing the lungs. However, the presence
of a congenital
lung lesion does not in itself increase the risk of prematurity.
It is important to realize that the accuracy of the diagnosis,
although very good, is not 100% perfect. The condition most resembling
lung lesion is congenital
diaphragmatic hernia. In
this condition, a hole in the diaphragm allows intestines and other abdominal
organs to move into the chest cavity, thereby compressing the
lungs. The effect of a diaphragmatic hernia on the lungs of the fetus
is similar to that of a congenital lung lesion. However, a diaphragmatic hernia does not get better during
pregnancy, and many of these infants are born with hypoplastic lungs. With current imaging techniques
(ultrasound and MRI),
the diagnosis of a diaphragmatic hernia can almost always be
differentiated from a lung lesion (bronchogenic cyst, CCAM or sequestration) (figure 2)
Figure 2: MRI of a diaphragmatic hernia (arrow: intestines
in the left chest. *Liver and right side of diaphragm, normal)
CAN BE DONE BEFORE BIRTH?
In most cases, the lesion will
eventually regress without causing any permanent damage. If this
can be predicted to occur, there is of course no reason to intervene
before birth. It will be important, though, to follow the lesion
closely, usually with weekly ultrasounds, until it is clear that
the lesion is getting smaller. In addition, it may be helpful
to obtain a fetal
resonance imaging): this test may give more information than
the ultrasound about the exact appearance of the lesion, possible
feeding blood vessels, and the condition of the surrounding normal
lung. It can help differentiate cystic lung lesions from congenital lobar emphysema or diaphragmatic hernia.
If the lesion seems to grow too
much, and early signs of heart failure are seen, something may
have to be done. If this occurs after 25-26 weeks of pregnancy,
it may be safer to think about early delivery, rather than to
continue the pregnancy or even to intervene directly on the fetus.
This is only recommended if the life of the fetus is believed
to be at risk, since such extreme prematurity carries an important
risk of complications.
If signs of heart failure occur
earlier in pregnancy (before 23-24 weeks), early delivery is
not an option, since infants of that gestational age cannot survive
outside the womb. Intervention on the fetus may be possible,
although this is obviously an invasive and risky procedure. If
the lesion consists mainly of one or two large cysts, it may be possible to remove the fluid
inside those cysts,
thereby collapsing the lesion and allowing heart and lungs to
function better. This procedure, called thoracentesis, is usually performed under
local anesthesia and constant ultrasound guidance. A long, thin
needle is introduced directly into the womb, and into the fetus's
chest. Fluid is aspirated from the lesion, and the needle is
withdrawn, or a "double pigtail" catheter is left behind.
This will then continue to drain fluid from the cyst into the amniotic cavity.
In rare cases, the lesion continues
to grow and threatens the well-being of the fetus, but no single
can be identified. In these cases, when the lesion is mostly
solid, the only option may be to remove the lesion surgically.
This type of fetal
surgery is the most invasive and riskiest form of intervention
on the fetus, and can only be performed in specialized centers.
Although this can be life-saving, not all babies can be saved,
and the procedure carries some risks to the mother as well.
If the lesion does regress, as
is seen in the majority of cases, no prenatal intervention is
needed. It may be important to plan for the delivery, however:
1. Mode and timing of delivery
While Cesarean section can sometimes be indicated for certain
conditions of the fetus, there is no need for it in the case
of a congenital
lung lesion. Of course, a Cesarean section may still be performed
for obstetrical reasons.
As mentioned before, prematurity
may increase the risk of complications for the newborn baby.
Since the lesions usually regress toward the end of the second
trimester or the beginning of the third trimester, pre-term delivery
is usually not indicated, unless there are signs that the fetus
is in trouble.
2. Place of delivery
Because of the risks of lung failure in the newborn infant, and
the possibility of early hydrops in the fetus, it is recommended that
the baby be born in a hospital that has immediate access to a
tertiary neonatal intensive care unit. In some cases, the lesion
is still sufficiently large at birth (particularly if the baby
is born prematurely) that immediate surgical intervention is
necessary. For that reason, presence of pediatric surgical specialists
is also advisable.
HAPPEN AT BIRTH?
If everything goes as planned,
you will deliver at a tertiary care center with direct access
to a neonatal intensive care unit. The neonatologists will be
present at delivery, so that they can immediately assess your
baby and start treatment, if necessary. At the same time, the
pediatric surgeons will be alerted. In many cases, however, you
will be able to see (and hold) your baby after delivery.
Your baby will be "stabilized"
in the intensive care unit. An intravenous line will be placed
in an arm or a leg, so that fluids can be given. If you baby
shows signs of distress, it is possible that he will be intubated, so that we can help him breathe
If it is clear that there are
no other major problems, your baby will undergo imaging tests
to look for the lesion. If he is stable and breathing well, a
chest X-ray and/or an ultrasound will be obtained, usually within
one or two days. Even if the lesion had "disappeared"
by prenatal ultrasound, it can usually be found by ultrasound
or chest X-ray after birth, since imaging the baby directly can
show more details than when the fetus is still in the womb.
Babies who breathe well and show no other signs of distress don't
need immediate intervention. Typically, your baby will be allowed
to go home, and plans will be made to be seen by a pediatric
surgeon. Even if there are no symptoms, surgical intervention
may be recommended later in infancy (typically, between 6 and
18 months), to avoid long-term complications of the lesion. In
some cases, this can be done using minimally invasive techniques (thoracoscopy);
in others, the operation will be performed using a thoracotomy.
Figure 3: Thoracoscopic view of a resected bronchogenic cyst
If the infant has breathing difficulties
and it is felt that this is due to the lesion, more urgent intervention
may be necessary. This can be done immediately after birth, or
later in the newborn period. The results of the operation and
the outcome for your baby depend primarily on the severity of
the condition and the degree of prematurity. Surgical removal
of part of a lung is an invasive procedure, but one that can
be performed safely in even the smallest of patients. Even if
a portion of normal lung has to be removed or if the lesion has
prevented full development of the normal lung, full recovery
is likely: normally, lungs continue to grow until a child is
several years old.
AND LONG-TERM OUTCOME
The overall outcome of congenital lung lesions (CCAM, bronchogenic cyst, sequestration) is generally excellent, if
the lesion has substantially shrunk by the time of birth. As
mentioned before, CCAM and intralobar sequestrations are at a significant risk of
recurrent infections (pneumonia). The infected cysts may look like lung abscesses - the knowledge of an underlying
lesion greatly facilitates the diagnosis. Pneumonia and other
lung infections are treated with antibiotics, but recurrence
of infections can be avoided by surgically removing the lesion.
In a small number of patients,
the lung lesion (usually a CCAM) may harbor a malignant tumor later in life. This is another
reason to recommend surgical removal of the lesion in early childhood,
even if your child has never shown any symptoms.