Congenital Cystic Lung Disease

Dr. Ali M AhmadMBBCh, MS, MD, MRCS-Ed, EBPS

Associate Pediatric Surgery; KAAUH_ PNU

Embryology and pathology

• Lower respiratory system begins to form in 4th week of gestation as a median outgrowth from the caudal end of the ventral wall of the primitive pharynx.

• This outgrowth known as the laryngotracheal groove evaginates to form the laryngotracheal diverticulum, which elongates to form the lung bud.

• Tracheoesophageal folds fuse to form the tracheoesophageal septum, which separates the foregut from the laryngotracheal diverticulum.

• Lung bud divides into two bronchial buds in 5th week & enlarge to form the primary bronchi

• These soon divide into secondary bronchi and tertiary bronchi by the 7th week. By 24 weeks, 17 orders of branches have formed.

• The endoderm lining of the laryngotracheal tube gives rise to the lower respiratory epithelium.

• The mesenchyme surrounding the laryngotracheal tube gives rise to the connective tissue, cartilage, muscle, and vessels.

1.Congenital Cystic Adenomatoid Malformation (CCAM)

2.Pulmonary sequestration (PS)3.Congenital lobar emphysema (CLE)4.Bronchogenic cyst (BC)

Congenital Cystic Lung Disease

Type I: large cyst (>2 cm)

Macrocystic CCAM.Large multiloculated cysts.They are the result of terminal bronchiolar proliferation with associated suppression of alveolar development. They are not true cysts and always communicate with the proximal airway and distal lung parenchyma.Histologically they are lined with respiratory ciliated cuboidal or columnar epithelium

1- CCAM

Type II: small cyst (<2 cm)

• Microcystic CCAM • These consist of small uniform multiple or multilocular

cysts. • They are not true cysts and are also lined by ciliated

columnar or cubical epithelium.

1- CCAM

Type III: solid lesion

• These are macroscopically and microscopically solid lesions without cysts.

• Pathologically these are grouped into the pulmonary hyperplasia group.

1- CCAM

Commonly,Affect a single lobe Affect both lungs and all lobes with equal frequency. They are infrequently associated with hydrops or pulmonary hypoplasia unless they attain a very large size. Generally asymptomatic at birth and have a favorable prognosis. Associated anomalies are very uncommon.

1- CCAM

• Nonfunctioning Cystic mass of lung parenchyma without communication with TB tree and with an anomalous systemic blood supply.

• Typically, these lesions have a single large feeding vessel arising from the aorta, but multiple vessels have been reported. Their venous drainage is variable and can be systemic, bronchial, or azygous.

2- PS

1. Intralobar: invested by the same pleura, commonly at LL basilar segments and more on the left than the right. These account for the majority of sequestrations.

2. Extralobar: outside the investing parietal pleura, commonly found in the lower hemithorax but have been reported in the upper thorax, below the diaphragm in the upper abdomen (15%), in the mediastinum, and in the pericardium.

• In 50% associated with other anomalies, namely congenital diaphragmatic hernia, eventration, esophageal duplications, and tracheoesophageal fistula

2- PS

• Results from obstruction of a lobar bronchus leads to progressive airtrapping and overinflation. – Intrinsic (bronchomalacia, webs, stenosis)– Extrinsic (Bronchogenic cyst, vascular

structures)– Up to one-third of cases are idiopathic.

• Histological, the lung parenchyma is normal with enlargement of the airspaces only.

• CLE commonly affects the upper lobes particularly the left.

3- CLE

• Most commonly:– Mediastinal In Location– Solitary Unilocular Cysts – Filled with fluid or Mucus.

• Often attached but do not communicate with

the TB tree • Histological: they are lined with pseudostratified

ciliated columnar epithelium with goblet cells and always have hyaline cartilage plates in their wall.

4- BC

OTHERS – Rare congenital lung lesions

Simple Lymphatic CystSimple Parenchymal CystEnteric CystMesothelial CystLow-grade Cystic Pleuoropulmonary BlastomaYellow Nail Syndrome With Cystic Lung DiseaseCongenital Pulmonary Lymphangiectasis

Prenatal Diagnosis and Management

Cystic lung lesion is the most commonly identified on routine prenatal US {accuracy > 70%}

Cystic lesions at lung bases can be confused with a CDH or pul sequestration can be confused with CCAM if US does not identify systemic arterial vessel on Doppler.

In these unclear cases, ultrafast MRI can provide more detailed anatomic assessment to make a diagnosis.

Prenatal Diagnosis and Management

• Serial prenatal imaging has allowed better understanding of the natural history of these lesions, and also aided in deciding on fetal intervention strategies when necessary.

• 15% of CCAMs and 70% of PSs decrease in size & mechanism of involution remains to be identified.

• > 1.6 was predictive of fetal hydrops and need twice-weekly US for fetuses less than 28 weeks gestation.

• >1.6 + fetal hydrops, need fetal therapy

Cyst Volume \ Fetal Head

Circumference Index

Fetal intervention

1.Thoracentesis2.Thoraco-amniotic

shunting

3.Open fetal surgery with in utero resection (if 32 wks)

4.Ex utero intrapartum therapy resrection, or just early delivery with postnatal resection if >32 weeks

Postnatal Presentation• Depending on the size, location, type of lesion, and whether

it communicates with the airway or the GI tract.

• Some infants may develop pulmonary hypertension and respiratory failure related to pulmonary hypoplasia. Some of these infants require ECMO for support and have an increased mortality rate.

• Other infants may experience left to right shunting (in PSs), and some can develop symptoms secondary to overinflation (in CCAMs and CLE).

• Some infants can remain asymptomatic and escape diagnosis for many years only to present as an incidental findings on routine radiography.

Virtually all patients eventually develop complications

The most common is pneumonia that is poorly responsive to medical therapy. Pneumonia occurs as a result of: retained secretion in lesions that communicate with the TB tree (CCAM, CLE) or as hematogenous seeding in the lesions that do not communicate with the airway (sequestrations).

Other complications include pneumothorax, hemithorax

Extralobar sequestrations may be found in association with cardiac and diaphragmatic anomalies in 50% of the cases.

Congenital Cystic Lung Disease

Dr. Ali M AhmadMBBCh, MS, MD, MRCS-Ed, EBPS

Associate Pediatric Surgery; KAAUH_ PNU

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