What is Lung Malformation in children – causes, symptoms & treatment in Malaysia
What are Lung Malformations?
Lung malformations are abnormally formed mass of lung tissue in children. These include: Congenital Pulmonary Airway Malformation (CPAM) or previously called Congenital Cystic Adenomatoid Malformation (CCAM), Broncho-Pulmonary sequestration (BPS), Congenital Lobar Emphysema (CLE).
The different anomalies listed above arises at different stages of the developing fetal lung creating varied types of malformation, though, there are no known cause for why lung malformations happen.
They may be within the lung lobes (intralobar) or outside the lung lobes (extralobar). CCAM or CPAM and Congenital Lobar Emphysema (CLE) are found within lung lobes whereas Broncho Pulmonary Sequestration (BPS) could be found within the lung lobes, outside the lobes but within the chest cavity or even in the abdomen.
How common are Lung Malformations?
The incidence of lung malformation is roughly 1 in 20000 to 30000 children. The vast majority of these are CPAMs. Males and females are equally affected. It effects a single lobe of the lung in 95% of babies (usually the lower lobes for CPAM but the upper lobes for CLE) and it effects both sides in less than 3% of all cases.
How do Lung Malformations happen?
In the early fetal period, the lungs develop from a pair of lung buds that gives rise to the main airways, the trachea, and then the right and left main bronchus and subsequently, bronchial divisions and these end with sponge like air sacs called alveoli. It’s much like a large tree with its main trunk, giving rise to branches, in this case the bronchial branches and the alveoli (air sacs) much like the leaves. (see diagram below).
Theory of how BPS ( Broncho-pulmonary sequestration) forms
The possible origin of BPS is an additional bud (at the very beginning of the formation of the lungs) that forms with the 2 main lung buds creating the left and right lungs. This additional bud of lung tissue does not connect to the airway and it migrates down towards the diaphragm.
If it’s included in the lung lobe at the bottom it is termed an intra-lobar BPS. If it doesn’t, it’s an extra-lobar sequestration (see below on BPS).
The blood supply to this solid piece of lung tissue is from the main blood vessel from the heart called the aorta. So the main features of BPS are a blood supply from the aorta and there is no connection to the airway to make it air filled, hence a solid piece of tissue.
Theory of how CPAM (Congenital Pulmonary Airway Malformation) and CLE (Congenital Lobar Emphysema) forms
The main airways, trachea, bronchus and bronchioles ( see diagram above) are tubes that are surrounded by stiff cartilage rings along its way to prevent these tubes from collapsing. The postulated theory for the formation of the cystic type of CPAM is because the airway to thet segment or lobe of lung is floppy as they do not have good cartilaginous support, before the formation of the alveoli.
At this stage the fetus “inhales” amniotic fluid into the developing lung and because the airway is floppy, the fluid gets in but cannot be expelled out easily hence there is fluid trapping and cyst formation instead of normal alveoli (much like a floppy drinking straw, it’s easy to blow through it but on sucking the straw collapses and nothing can come up).
The same theory applies to the possible cause for CLE but at a stage after the formation of the alveoli. Here the alveoli has formed and the fluid trapping happens later in the pregnancy. For both these situations, the trapped fluid is replaced by air, once the baby is born and starts inhaling air.
In the case of the solid CPAM, it is thought that the bronchiole tissue grows abnormally in excess and instead of tubes, they form solid tissue and no alveolar tissue is made. They are not cystic as there are no tubes bringing in amniotic fluid or air into these abnormal parts of lung.
What is CPAM (Congenital Pulmonary Airway Malformation)?
CPAM is the commonest congenital lung malformation that are picked up antenatally now, with more advanced sonographic machines that are available to obstetricians and foetal medicine experts. These lesions can consist of many tiny cysts (microcystic), or fewer large cysts (macrocytic), a combination of both or solid tissue. They are classified into 5 main types, types 0 to 4. ( types 1 to 3 were in the original description and types 0 and 4 ware added later).
The table below shows the different types of CPAM, the relative percentage of each type, the way they present and the risks of malignancy:
Type 1 CPAMs are the most common making up to about 65% of all CPAMs and is composed of a single or multiple cysts which are bigger than 2cm in diameter. Typically they occupy no more than 1 lobe of lung and are asymptomatic when baby is first born. With the stagnancy of mucus within these cysts, there is possibilities of getting a lung infection. The risk of this happening is about 5%. The risk of malignancy is an estimate of about 3% as a lifetime risk.
Type 2 CPAM are the second most common type in up to 15-20% of all cases of CPAM. The cysts hers are smaller, less than 2cm in diameter. As the cysts are smaller, the risks of infections are smaller and there is no quantifiable risks for malignancies. However some children may have associated other abnormalities such as with the kidneys or heart that may give symptoms.
Type 3 CPAM occurs in about 5-10% of all cases and are usually large bulky non-cystic lesions which compress or pushes other organs (e.g. heart) or other normal lung lobes. Due to this compressive effects, it can push on the oesophagus, antenatally causing polyhydramnios and the baby cannot swallow the liquor or pressure on the heart causing hydrops. Post-natally, it can compress on good lungs causing diminished lung function. The malignancy risk here is negligible.
Type 0 CPAM are extremely rare. They usually involve the whole lung on one side and has a solid appearance with small and firm lungs. Usually this condition is not compatible with life. There is no malignancy risk observed with this.
Type 4 CPAM happens in op to 10% of CPAMs. They have large cysts which are more than 10cm in diameter and the cysts are usually on the surface of the lungs, superficially. Symptoms include infections or pneumothorax postnatally and they have a malignancy risk of about 5%.
Currently most CPAMs are diagnosed antenatally, usually at the foetal anomaly scans at 20 weeks’ into the pregnancy.
If any lung lesions are identified at this stage, a measurement called the CVR (CPAM-volume-ratio) is done with the ultrasound. This helps predict which foetuses are more likely to have problems during pregnancy. The measurement can be used for both CPAMs and BPS lesions. Another scan called the colour-flow Doppler is used to look for a feeding vessel from the aorta.
In some with a large lesion, a foetal MRI may be needed to further understand the shape, the size of the lesion and the effect it has on other structures. A foetal echocardiogram (special heart ultrasound) is used to assess how well the heart is working when there is a concern.
Babies with lung lesions usually have normal chromosomes. An amniocentesis is only recommended when other problems are present.
Very rarely, we get children presenting with lung infections as the initial indication of CPAM. Tumours in childhood arising from CPAM are extremely rare (more commonly in adulthood) though pneumothorax do occasionally occur. Some lung malformations are found after birth by x-rays or CT scans when children are evaluated for breathing problems or recurrent lung infections.
What is Broncho Pulmonary Sequestration (BPS)?
Broncho Pulmonary Sequestration contains immature lung tissue without connection to tracheobronchial tree (airway) and derives its blood supply from aberrant blood vessel from the aorta and usually has its venous drainage into the left atria of the heart along with the rest of the blood drainage from the normal lungs.
Again these lesions are picked up antenatally and as they are generally small in size, it does not cause any problems with breathing. Very rarely it can compress an adjacent normal lung to cause a lung infection. The main issue is with the blood flow into these lesions as they can “steal” blood from the aorta if their feeding vessel is large and drain blood back to the left side of the heart. This puts additional burden on the left side of the heart which will respond by enlarging. Follow up with Echo Cardiograms is essential for these lesions.
What are Hybrid lesions?
This term refers to the overlap between CPAM and BPS. Several surgical series have shown that some lesions do not fit neatly into the above two categories and have been labelled hybrids.
Features of hybrid lesions include:
- Anatomical extralobar sequestration with histological appearance more compatible with CPAM. (Once taken out surgically, the lab analysis of the sequestration shows features of CPAM)
- BPS and CPAM occurring in the same child.
- Obvious CPAM-lesions in a lobe (cystic) but with an accessory systemic blood supply.
What is Congenital Lobar Emphysema (CLE)?
CLE as described above is a condition where there is air trapping in a lung lobe or segment. This problem can be progressive, getting worse with time, hence regular follow up with imaging is important if surgery is not indicated initially.
The enlarging CLE can cause compression on normal lung, the esophagus, or even the heart. They also have a risks of lung infections.
How are Lung Malformations treated and managed?
All lung lesions are evaluated and managed in a similar way during foetal life. Although most of these lesions stop growing around the 26th week of gestation, some continue to grow throughout the pregnancy, so they need to be monitored closely. More than 90 percent of babies with prenatally diagnosed lung lesions will not have any foetal problems.
The monitoring is to help avoid problems such as polyhydramnios, mediastinal shift and hydrops (i.e. skin oedema, pleural effusion (fluid in the chest cavity) or ascites (fluid in the abdominal cavity). The development of hydrops is probably the most serious situation for the foetus and prognosis for the pregnancy.
The other factors often described for the antenatally diagnosed lung masses is the CPAM volume Ratio (CVR). CPAM volume is calculated by the measurements of lung mass in three perpendicular planes and the CVR is calculated by dividing the CPAM volume by head circumference (HC, measured in centimetre). Thus CVR = (L × B × W × 0.52/HC). The CVR is another tool to assess the severity of lung malformations, though interventions are available, (listed below) to deal with the complex lung lesions.
In the past, mothers whose foetuses presented with a diagnosis of CPAM were informed of poor prognosis and advised for termination. However, with good antenatal surveillance follow up, and timely interventions, if required, termination is no longer appropriate (bar very rare complex malformations). There are also reports of disappearing lesions on serial ultrasound scan examinations.
Options for antenatal intervention for complicated lesions include:
- Maternal steroids (commonest): Expectant mother may be given steroid injections if they have foetuses with large microcystic lesions or with hydrops, early in pregnancy. Steroids seem to reduce the rate of growth of these lesions and improve hydrops. Steroids are commonly used for foetuses with larger lesions or any at risks of hydrops.
- Thoracoamniotic shunts: A CPAM with a single large cyst causing foetal hydrops or if there is significant pleural effusion ( large collection of fluid in the chest cavity) can be treated with a shunt. A shunt is a tiny tube to drain what’s in the foetus’s chest into the amniotic fluid in the womb. The shunt once inserted is left till the baby is born.
- Foetal lobectomy, foetal laser ablation of single feeding vessels are other interventions that are offered in other countries but not performed in Malaysia.
Delivery of baby
Though then majority of antenatally detected lung anomalies are asymptomatic once born, especially the smaller lesions (CVR < 1), it is advisable to deliver in a center where there is good neonatal services, if not at a center where there is a paediatric surgeon at hand.
Ideally delivery should be a planned event where parents to be had already consulted with the team who would be looking after both mother and baby and delivery should be at that center so a smooth early journey for the newborn is achieved.
There are no differences between vaginal delivery to a caesarian section for most babies.
The obstetrician will decide on the more complex lung anomaly or if there are any other issues with the pregnancy as to the mode of delivery.
Management once child is born
The baby will be monitored in a baby unit for the first 24 hours and an X ray of the chest will be taken. Usually the rate and pattern of breathing is assessed and the oxygen saturation of baby’s blood is monitored. The initial X Ray is to assess if the lung anomaly is visible on the plain X Ray. If so, how big is it and is it causing any issues with other surrounding structures?
A baby who has persistent breathing symptoms after a few days is likely have an early CT scan and proceed to surgery if both the symptoms and the CT scan analysis indicates that surgery is warranted at this stage.
The lobectomy can be conducted successfully by the thoracoscopic (keyhole method) way even for a neonate.
Fortunately, most babies do not have breathing issues in the first few months of life. Parents are advised for their babies is to undergo all their routine immunizations including Haemophilus Influenza and Pneumococcal Vaccines.
General precautions should be taken to avoid acquiring any respiratory illnesses especially from older siblings. At about 3 to 4 months of age, a CT scan of baby’s chest is conducted to analyse the lung lesion. Even the antenatally “disappeared” lesions should have a CT scan as studies has shown that up to 40% of the “disappeared” lesions ended up having surgery.
Once the CT scan is done then the paediatric surgeon will discuss if surgery is required for your little one.
Is surgery always required to treat Lung Malformations?
If at any point there had been symptoms or if there was lung infection, it is strongly recommended to have a lobectomy(remove the lung lobe) of the effected CPAM lobe. Bear in mind that every lung infection (pneumonia) makes surgery more difficult due to the scarring that it causes inside.
Abnormal lungs are removed to reduce the risk of infections, malignancy or if it is a large lesion, it may compress the good functioning lung tissue or other structures such as the heart. If surgery is done early, there is compensatory lung growth. Essentially the lung tissue continues maturing and growing till about 2 years of age and removing lung before the end of this period allows for regrowth of lung, as if it was never removed.
However the benefit of surgical excision and the risks of surgery (though small) should far outweigh the risks of leaving the abnormal lung tissue behind.
Let’s look at the various types of CPAM classified above and their risks from current available evidence:
Type 1: large cysts with risks of infection and malignancy – best to remove
Type 2: Smaller cysts with minimal risks of infection or malignancy- excise if large or if symptomatic
Type3: Solid structure with minimal risks of infection or malignancy but they are usually large- excise if large or if causing symptoms
Type 4: Very large cysts on the periphery of the lung with high risks of infection, malignancy and pneumothorax – best to remove
Type 0: extremely rare, usually effecting whole lung – need individual assessment and management
CLE can gradually worsen over time so it’s best to monitor closely. Simple chest xray may suffice for follow up as they can often be seen on these. They usually require a lobectomy to avoid lung infections and worsening of the emphysema.
The BPS can cause pressure effect on adjacent structures or more commonly the issue is with the vascular blood flow effect. Generally BPS are excised as the could cause long term effects on the heart size and function. More recently embolization (blocking the feeding blood vessel from the aorta) has been described for BPS. The long term outcome for this technique unknown hence most surgeons are anxious about this as a sole procedure without excision.
When should surgery be conducted for Lung Malformations?
Surgery is usually recommended at about 8 to 10 months of age.
This is a good age where babies are more robust to undergo an elective surgery and also allow enough time for regeneration of new lung tissue after the lobectomy.
Surgical Treatment for Lung Malformation
Lung lobectomies or excision of BPS can be performed by the traditional open technique, called thoracotomy or by the minimally invasive method otherwise called thoracoscopic method.
Thoracotomy involve an incision to the side of the chest anything from 4 cm wide, parallel to the ribs. Whereas thoracoscopic procedure involved 3 or 4 incisions, most are 3mm in width except for one which will be “stretched” to 10mm length to retrieve the lobe out.
Here a small “telescope” is used into the chest cavity for the surgeon to visualise the area involved and a few (2 or 3) instruments are required to delicately separate and detach the effected lobe or sequestration. The tissue is then gently manipulated out of the chest. The wounds are closed with some sutures inside and glue on the skin. ( see pictures below)
Recovery and outcomes after Lung Malformation surgery
With the keyhole method, children do not have much pain after the surgery. The chest tube is usually removed the next day, provided nothing is draining through it.
The average stay in hospital after this procedure is about 3 days. Surprisingly children are back to their normal functioning by this time.
One week after surgery a follow up appointment will be made to check on the wounds and to discuss the histological findings (laboratory analysis) of the excised lung tissue. There will be another assessment at about 3 months post-surgery and subsequently, the follow up would be with a respiratory physician.
Most children would regrow new lung tissue by 2 years of age and usually do not require any medications. However a few may need some help with their breathing with inhalers hence it’s important to follow up with a paediatric respiratory physician, who would confirm a normal lung function before being discharged from follow up.
The outcome of the overall process of going through lobectomy surgery and subsequent recovery is excellent.
Can Lung Malformation happen in a mother’s subsequent pregnancy?
Lung malformations happens due to an abnormality during the formation of the lungs and not genetic and there are no familial association (run in families). It is a sporadic (by chance) event for that pregnancy.
So the chance of it happening again is extremely unlikely.