Congenital pulmonary malformations are rare lesions
that form during the embryological development phase of the
lungs. The rate of diagnosis for congenital pulmonary malformations
in both the prenatal period and adulthood has
increased as a result of the advances in imaging methods. In
infants, it often presents with respiratory distress and requires
urgent diagnosis and treatment. In older children and adults,
it either remains asymptomatic or progresses with recurrent
pulmonary infections. will thus play an important role in future
coronary artery stent imaging with its high spatial resolution
and rapid acquisition.
Bronchogenic Cysts
BC is the most common form of congenital cystic lesions
in the mediastinum. BCs account for 34% of the cysts,
6.3% of the mediastinal masses, and almost half of all congenital
mediastinal cysts 5.
Bronchogenic cysts are benign congenital lesions
that form as a result of abnormal budding from the primitive
tracheobronchial tube during the developmental phase of the
respiratory system. They may be detected in any age group.
The cysts are usually solitary, thin-walled, and unilocular. Rarely,
they may be multiple or multilocular. Three-fourths of the
cysts are located in the mediastinum, while one-fourth are
intrapulmonary. In the mediastinum, BCs are most frequently
located in the pericarinal area followed by the right trachea
and hilum. They are rarely found in the posterior and/or anterior
mediastinum. Intrapulmonary BCs are usually located in
the lower lobes. The cysts contain bronchial cartilage, smooth
muscle, elastic tissue, and mucous glands. Internally, they contain
a mucoid fluid. Histopathologically, the internal cystic wall
is covered with a ciliary columnar or cuboidal epithelium.
Although BC is a congenital anomaly, it is often detected
in the adults, particularly in adult males. It is most commonly
detected between the ages of 30 and 40 years 6.
BCs may be symptomatic or asymptomatic. The
symptoms vary depending on the location and adjacent structures.
Of BC patients, two-thirds are asymptomatic, and the
cysts are frequently detected in adolescents and adults 7.
The mediastinally located cysts generally have a more latent
progression, whereas those located in the parenchyma become
symptomatic because of their proximity to the bronchial
tree. Of intraparenchymal cysts, 20% are accompanied by infection.
The most common symptoms are chest pain, coughing,
and dyspnea 8. Our patients had similar symptoms. The cysts are generally thin-walled, unless they are infected. When
infection develops, the cystic wall becomes thicker and squamous
metaplasia may develop on the epithelium that covers
the internal cyst. Cysts have close relations with the tracheobronchial
tree and esophagus. In case of compression of the
tracheobronchial tree, infection, hemorrhage, or rupture, they
may be life-threatening.
Mediastinal bronchogenic cysts are well demarcated
and homogenous on pulmonary graphs. The cysts may contain
thick fluid. During thoracic radiography of intrapulmonary
cysts, air, fluid, or air-fluid levels can be observed 9. BCs are
rarely detected through prenatal sonography, and CT is highly
useful in diagnosis and forming differential diagnosis. In suspected
cases, MRI provides additional information in differentiating
cystic from solid lesions. Barium studies can show the
abnormal relation between the respiratory tract and esophagus
or stomach.
On differential diagnosis, esophageal duplication
cysts, neuroenteric cysts, CCAM and cystic teratoma, timic
cyst, or ectopic thyroid tissue that undergoes cystic transformation,
particularly when BC is located in the anterior mediastinum,
should be kept in mind 5.
BCs are histopathologically diagnosable and have a
low malignancy potential. Thus, to avoid any complications,
they require surgical treatment. Total excision is efficient in
those with mediastinal cysts; however, BCs located intraparenchymally
require wedge resection, segmentectomy, or
lobectomy. Despite being a benign anomaly, they may recur if
not completely resected 10. Lobectomy can be performed if
atelectasia or pneumonia is frequent around the cyst. In case
of small cysts, anatomical segmentectomy is proper. Three
of our patients with an intraparenchymal lesion received a
cystectomy and capitonage. Two lesions located mediastinally
were resected through right thoracotomy.
Pulmonary Sequestration
PS accounts for 0.15–6.4% of all the congenital
pulmonary malformations 11. PSs are abnormal pulmonary
tissue that may be located inside or outside of the lungs. Vascularization
of the lesion, which has no direct contact with
the tracheobronchial system, is provided by systemic arteries.
Depending on its relation with the pleura, there are two
types o f PS: intralobar and extralobar. Those that arise before
the visceral pleura is formed are termed intralobar pulmonary
sequestration (ILPS), and those that arise after the visceral
pleura is formed are termed extralobar pulmonary sequestration
(ELPS). Both types have been shown to have an embryogenic
origin. Stocker and Malczak hypothesize infection as
the etiology of intralobar sequestration 12. This hypothesis
is supported by the common symptom of recurrent pneumonia
and the presence of patients with purulent bronchiectasis.
On the other hand, detection of intralobar sequestration, not
accounted for by infections, indicates a congenital etiology. In
both types, blood flow is provided by the aorta or its branches. Generally, the venous circulation of ELPS is through
systemic veins (v. azygos, v. hemiazygos, vena cava), while in
ILPS, it is through pulmonary veins 11. ILPS accounts for ¾
and ELPS for ¼ of all pulmonary sequestration cases. All of
our patients with pulmonary sequestration had ILPS.
The vascularization of ILPS is usually provided by an
aberrant branch arising from either the thoracic aorta or abdominal
aorta. Intralobar sequestration is rare in other congenital
anomalies. There may be a shunt from left to left, and
patients may suffer congestive heart failure. Although it is not
related to the bronchial system, if infected, it may discharge
into the bronchus. Nearly 60% of these cysts are located in
the lower left lobe and 40% in the lower right lobe. Upper
lobe involvement and bilateral involvement are very rare. Although
the segment with sequestration can be removed, in
most of the reported cases, lobectomy was performed. In our
series, 3 patients with cysts in the left lower lobe and 3 patients
with cysts in the right lower lobe underwent lobectomy.
ELPS is adjacent to the left diaphragm in 90% of cases. It is
usually located under the left lower lobe, and, in very rare
cases, under or in the diaphragm. Its systemic artery usually
arises from the abdominal aorta. It is four times more common
in males than in females. The presence of intralobar and
extralobar sequestrations in the same patient is rare. ELPS
is frequently accompanied by diaphragmatic hernia among
other congenital anomalies. Because it has its own pleural sack, the risk of infection is lower, and, unless infected, it remains
asymptomatic. The treatment is the resection of the
sequestrated lobe.
The detection rate of ELPS is higher in the prenatal
and neonatal periods, while ILPS is usually detected in childhood.
In neonates and infants, sequestration is usually accompanied
by recurrent lower lobe pneumonia. In childhood,
most patients are asymptomatic. ELPS is usually large enough
to cause respiratory distress in the neonatal period. ILPS tends
to be smaller and is often incidentally detected in children
and adolescents after an infection 9. Three of our patients
applied with recurrent lower lobe pneumonia.
In the prenatal period, diagnosis can be established
by ultrasonography (USG) in the 4th-6th months. Prenatal MRI
can show a well demarcated and defined mass with high density.
On a direct thoracic radiograph, PS is classically observed
as a basal mass with three corners or an oval shape, located in
the posterior. Cystic pulmonary tissue containing air or air-fluid
may be seen. Bronchiectasis, atelectasis, mediastinal shift,
and a marked hilus on the same side are other commonly
seen radiological findings. CT provides information on the location
of the sequestration and the pulmonary parenchyma.
Colored Doppler USG and MRI are superior to CT in reflecting
the systemic arterial circulation. Differential diagnosis of PS
involves tumoral lesions such as CCAM, other congenital pulmonary
malformations, diaphragmatic hernia, Wilms tumor, neuroblastoma, and teratoma and accessory spleen 9.
Some authors advocate conservative treatment in
most patients with PS and recommend surgery only when
complications arise. Severe complications such as fungal infection,
tuberculosis, fatal hemoptysis, hemothorax, cardiovascular
problems, benign tumors, and even malign degeneration
associated with PS have been reported 13. Thus, the treatment
of choice for PS is surgical resection. During resection,
the aberrant artery should be ligated. Otherwise, the artery
that shifts into or under the diaphragm may lead to uncontrollable
hemorrhage. Another important point is to clearly define
the venous circulation in order to avoid pulmonary infraction.
Congenital Lobar Emphysema
Congenital lobar emphysema was first reported in
1932 by Nelson 14. It is usually characterized by hyper-inflammation in one lobe. The left upper lobe (50%) and the
right middle lobe (30%) are most often involved, followed by
the right upper lobe. More than one lobe may be affected.
However, involvement of lower lobes is rare. The incidence in
male children is three times higher than in female children. Of
the four patients with CLE in our series, two were male and
two was female. The lesions were located in the left upper
lobe in two patients, in the right middle lobe in one patient
and in the right upper lobe in one patient.
The etiology for CLE is not known for almost half of
patients. Entrapment of air due to the valve effect of the dysplastic
bronchial cartilage, mucous plaques in the bronchus,
aberrant veins compressing the bronchus, and infections causing
bronchial disorders are some of the known etiologies 15.
In addition, one etiology of CLE involves polyalveolar lobe formation
by numerous alveoli with normal size. No destruction
occurs at the alveolar wall. However, the alveolar count is 3-5
times higher than that of normal parenchyma. The incidence
rate of coexisting CLE and congenital heart failure is 20%.
Anomalies such as renal agenesis, renal cyst, pectus excavatum,
diaphragmatic hernia, and extremity anomalies may also
coexist 16.
Most of the patients are symptomatic in the neonatal
period. Myers has classified CLE into 3 clinical types: CLE
type I, symptomatic in infants, CLE type II in adolescents, and
CLE type 3 in asymptomatic patients with incidental diagnosis
17. Types 2 and 3 are rare. The onset of the symptoms is
usually in the first week in half of the patients and within 6
months in the other half. The number of reported cases with
CLE detected in the adulthood is very limited. The most common
symptom is respiratory distress. CLE is the most common
etiology for Neonatal Respiratory Distress Syndrome and is
usually seen in the first six months of life. Three of the four
CLE patients in our series were under six months of age, and
the other was three years old.
On physical examination, hypersonority, reduced respiratory
sounds, and deviation of the trachea to the opposite
side are detected in the involved side. Compression of healthy pulmonary tissue results in dyspnea, cyanosis, reduced venous
circulation, hypertension, and eventually cardiac arrest.
The diaphragm may shift downwards bilaterally. Direct thoracic
radiography is usually sufficient in establishing a diagnosis
of CLE. In suspected cases, CT aids in diagnosis 9. On
thoracic radiograph and CT, hyperlucency, collapsed adjacent
lobe, and mediastinal shift as well as hernia of the hyperin-
flamed lobe to the other side are observed. On CT, tense and
thinned veins are also observed in the emphysematous lobe.
The differential diagnosis includes pneumothorax,
pulmonary hypoplasia, pneumotocele and endobronchial
mass, and CCAM. Congenital diaphragmatic hernia and foreign
body aspiration should also be kept in mind. In many
cases, tension of the lobe (excessive air) is mistaken for pneumothorax,
and a thoracostomy was performed. This will not
lead to clinical relief. Rather, it deteriorates the present clinical
picture.
In infants with severe respiratory symptoms, pulmonary
resection is needed to avoid morbidity and mortality.
The recommended treatment is lobectomy. However, some
authors have reported that, in asymptomatic patients or in
patients with minimal symptoms, conservative treatment can
be applied 18. Infants with severe respiratory distress may
need urgent thoracotomy or lobectomy. Intraoperatively, until
the thorax is penetrated, excessive expansion of the lungs
should be avoided in order to prevent an increase in mediastinal
shift and compressive shock. After the thorax is opened,
the emphysematous lobe should be taken outside the chest
and lobectomy should start.
Congenital Cystic Adenomatoid Malformation
The incidence rate of CCAM varies between 1/4000
and 1/35,000 19. It is a congenital anomaly associated with
disrupted embryogenesis and characterized by anastomosing
proliferated terminal bronchioles of different volumes as
well as cystic and solid structures. Its etiopathogenesis has
not been fully described. It may be accompanied by cardiac,
renal, and chromosomal disorders. The pulmonary segment
affected by CCAM is not functional. However, because it is
highly vascularized, functional areas receive less blood. Therefore,
a right-left shunt and hypoxia are observed. With the
development of mediastinal shift, mortality associated with
left ventricle failure may occur.
CCAM is usually unilateral and located in one lobe
only. Miller et al., have reported equal rates of upper and
lower lobe involvement and lower rates for middle lobe involvement
20. Hacham et al., on the other hand, reported
a higher incidence rate for left lower lobe involvement by
CCAM 21. The patients with bilobar or bilateral lesions usually
have a poorer prognosis due to hypoplasia in the residual
lung. In three of our patients with type 1 CCAM, the lesions
were located in the left lower lobe, in the right lower lobe and
in the right upper and middle lobes. Nevertheless, the lesion
in the patient with coexistent CCAM and ILPS was located in the left lower lobe.
Bale has classified CCAM into three groups; cystic,
intermediate, and solid, while Stoker classified CCAM into
Type 1, Type 2, and Type 3, and then added Type 0 and
Type 4 22. Type 1 and Type 4 are at increased risk of malignant
transformation. Reports of patients with CCAM who
developed rhabdomyosarcoma exist 16. Type 1 is the most
common form and has the best prognosis. Type 2 is usually
accompanied by other congenital anomalies. Type 3 usually
results in death at birth.
CCAM may present with pulmonary hypoplasia, fetal
death, severe fetal hydrops, and intrauterine retardation.
Half of the pediatric or adult patients of CCAM present with
symptoms of pneumonia. In newborns, inflammation of the
lesion area is rare, whereas in adults, it is more common 23.
Despite antibiotic treatment, no radiological improvements
are observed, and symptoms tend to recur. CCAM is very rare
in adults. Entrapment of air within the lesion leads to a mediastinal
shift. CCAM is the second most common reason for
neonatal distress syndrome.
The diagnosis of CCAM can usually be established
by USG in the prenatal period. Matsuoka et al. have recommended
MRI to aid in the diagnosis of atypical patients with
multiple anomalies in the prenatal period 24. The presence
of fetal hydrops and cysts < 5 mm and with a solid appearance
denote poor prognosis 25. Hemodynamic changes due
to cardiac compression have been shown to cause hydrops.
Despite the ability to identify anomalies using USG, thoracic
radiography of most newborns is normal. In the postnatal period,
lesions are easily found on CT. Through imaging modalities,
abnormal air is observed in CCAM type 1, air-fluid level
in type 2, and fluid-filled cysts with solid structure in type 3.
Definitive diagnosis, however, can be established through histopathological
evaluation.
CCAM is most frequently mistaken for congenital diaphragmatic
hernia. Nevertheless, it can be differentiated from
a diaphragmatic hernia by observing the normal gas in the
diaphragm or abdomen. Other differential diagnoses include
intrapulmonary bronchogenic cyst, pulmonary sequestration
(PS), congenital lobar emphysema, cystic bronchiectasis,
pneumotocele, and necrotizing pneumonia. Intrapulmonary
bronchogenic cysts can be differentiated because they are
solitary lesions with wall cartilages and have no connection
with alveoli. In PS, the artery running from the systemic circulation
is observed within the involved lobe. In lobar emphysema,
there are no alveoli between the cysts. A pneumotocele
complex does not contain epithelial or stromal components.
In children, it may be difficult to differentiate CCAM from
necrotizing pneumonia that progresses with recurrent infections.
The presence of recurrent infection, hyperextension of
the affected lobe, and the absence of air bronchograms in the
same location is suggestive of CCAM. Richard et al. reported
that 50% of the patients with extra-lobar sequestration also
have accompanying CCAM 26.
Patients with CCAM should be treated surgically even
if they are asymptomatic because of the risk of malignancy.
Lobectomy is the treatment of choice. If the lesion is located
in one segment only, segmentectomy will suffice. However,
pneumonectomy should be avoided. Patients who undergo
surgical treatment have an optimal prognosis.
In conclusion, congenital cystic pulmonary anomalies
may lead to life-threatening respiratory distress in infants.
They may progress with recurrent pneumonia in children and
adults and have potential for malignancy. Surgical treatment
is required to eliminate symptoms, prevent complications, and
establish a histopathological diagnosis.
Conflict interest statement The authors declare that they have no conflict of interest to the publication of this article.
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