CONGENITAL ABNORMALITIES OF THE LUNG Damian Gimpel Waikato Cardiothoracic Unit

Take home messages Many of these lung lesions can be diagnosed in utero. For some large cystic lung lesions it is possible to intervene prenatally The clinical presentation of these congenital lesions varies considerably, from a neonate in extremis to an asymptomatic adult. Resection of the affected portion of the lung nearly always will be necessary. Long-term results are generally very good.

Embryology https://www.youtube.com/watch?v=-fY1yCaxwxQ

embryology The lung parenchyma and vascular supply develop initially separate from one another. During the embryonic phase of pulmonary development, as early as the third week of gestation, the lung buds begin as outpouchings of the primitive foregut.

embryology Over the next 3 weeks, the lungs develop five distinct components ultimately to become the lobes. It is during this phase that the pulmonary arteries and veins become associated with the developing lung buds. The pulmonary arteries arise from the right and left sixth aortic arches and extend toward the developing lung bud

embryology The pulmonary veins begin as an outgrowth of the dorsal wall of the atrium divides into right and left pulmonary veins that then extend into the lung at the same time as the arterial development The common pulmonary vein then becomes incorporated into the atrial wall as it develops

The pulmonary arteries follow the bronchi, but the veins do not. embryology The pulmonary arteries follow the bronchi, but the veins do not.

embryology canalicular phase, the basic components to air exchange beginto develop, and by 28 weeks of gestation this pattern is firmly in place. development of type I and type II pneumocytes. alveolar period, these distal air spaces become more complex and multiply in numbers, forming mature alveoli. After birth, there is a continued increase in the number of alveoli until approximately age 8 years. From that point further, the alveolar size increases up to age 21.

FAILURE OF DEVELOPMENT OF THE LUNG BUD Agenesis Aplasia hypoplasia

agenesis result of failure of the primitive lung bud to develop This can be a bilateral process - universally fatal. The trachea ends in primitive lung tissue or just blindly Unilateral pulmonary agenesis - associated with other congenital anomalies, particularly when the right lung is absent No known chromosomal aberrations have been identified with this process. Prognosis

agenesis The presence of esophageal atresia or tracheoesophageal fistula has a particularly poor prognosis Many patients are asymptomatic because the total volume of lung tissue present can be almost normal due to compensatory growth of the contralateral lung The diagnosis may be made antenatally with ultrasound

agenesis Pulmonary function tests may demonstrate evidence of airway obstruction secondary to stretching of the main stem bronchus across the mediastinal structures. the overall survival of infants born with unilateral agenesis of the lung is somewhat poor, presumably because of the other associated anomalies but also due to airway issues related to the mediastinal shift and risk of infections.

agenesis

Aplasia Aplasia of the lung is essentially the same as agenesis from a functional standpoint In this case, a bronchial stump is present This may be a source for recurrent infections In those cases, resection of this stump may be indicated

hypoplasia Hypoplasia of the lung can occur as a primary process or be related to other conditions that compromise the thoracic space available for lung growth (i.e. diaphragmatic hernia) It is defined as deficient or incomplete development of one or both lungs.

hypoplasia Pulmonary hypertension frequently accompanies lung hypoplasia because of the diminished pulmonary vasculature Clinical manifestations of pulmonary hypoplasia depend on the volume of lung present but can include severe respiratory distress and cyanosis

hypoplasia This may occur in up to 20% of infants born after premature rupture of membranes at 15 to 28 weeks of gestation It is suspected in an infant with respiratory insufficiency and small lungs on chest radiography The lungs fail to develop to normal size but contain the usual distribution of bronchi. There are decreased numbers of alveolar ducts and alveoli for the number of bronchioles microscopically. The cause is unknown, and themortality rate is high

Congenital Lobar Emphysema CLE occurs when there is an obstruction in the bronchial tree that produces overexpansion of the air spaces of a segment or lobe of the lung In contrast to acquired chronic obstructive pulmonary disease seen in adults, the parenchyma itself is not destroyed, showing only air space enlargement

Congenital Lobar Emphysema inadequate development of the cartilage in the bronchi during the 18th week of gestation Almost half of the patients with this diagnosis have a distinct abnormality in the bronchus leading to the affected lobe abnormal mucous folds, intrinsic webs, bronchial stenosis, bronchomalacia

Congenital Lobar Emphysema It is also possible for CLE to develop from extrinsic compression of the bronchus by enlarged pulmonary arteries large left-to-right shunt or tetralogy of Fallot  enlarged central pulmonary arteries. This accounts for a small percentage of cases of CLE

Congenital Lobar Emphysema At least half of patients with CLE have no obvious abnormalit in the bronchus CLE may arise because of a so-called polyalveolar lobe. In this disease, there is a significant increase in alveolar number, outstripping the number of bronchi leading to them Air may enter these alveoli via collaterals and have no way to get out, resulting in overdistention of the affected lobe and thus CLE

Congenital Lobar Emphysema The upper lobes, particularly the left upper lobe, are affected more often than the lower lobes These lesions occur in the left upper lobe approximately 40% of the time in the right middle lobe in 35% of cases the right upper lobe in 20% males two or three times more frequently than in females

Congenital Lobar Emphysema The diagnosis is seldom made prenatally by ultrasound This anomaly has a variable clinical presentation Most infants develop symptoms of tachypnea, cough, and/or wheezing within a few days after birth. Symptoms usually progress and may lead to severe respiratory distress if the hyper expansion is sufficient to compress the trachea. Approximately half of patients with present within the first month of life. A few present as adults

Congenital Lobar Emphysema Physical examination typically demonstrates diminished breath sounds on the affected side chest may be significantly larger when viewed externally The diagnosis is usually made on the basis of the chest radiograph hyperlucency on the affected side with mediastinal shift to the opposite side, depression of the diaphragm, and compression atelectasis of the remaining normal lung

Congenital Lobar Emphysema CT of the chest is often helpful to establish the diagnosis, detect a possible underlying cause, and rule out foreign body aspiration Bronchoscopy may be helpful in defining extrinsic compression, but do not perform it if the infant is in severe respiratory distress

Congenital Lobar Emphysema Patients with isolated CLE who are symptomatic undergo thoracotomy with resection of the affected lobe Positive-pressure ventilation during the procedures can pose significant problems: worsening of the air trapping and further shift of the mediastinum with consequent hemodynamic instability The surgical mortality rate for CLE is approximately 15% and depends on the associated anomalies, which are usually cardiac

Congenital Lobar Emphysema It is clear that, in some patients with minimal or no symptoms, CLE can be managed conservatively Closely monitor these patients with serial chest radiographs and ventilation perfusion lung scans

Congenital Lobar Emphysema

Congenital Cystic Adenomatoid Malformation segmental bronchial atresia, perhaps resulting from primary disruption during fetal lung bud development or from disruption of the fetal bronchial circulation Lung growth beyond the atretic segment becomes dysplastic and may take on one of three distinct types

Congenital Cystic Adenomatoid Malformation Type I (55% of cases) consists of large cystic spaces within a single pulmonary lobe Type II (40%) appears as numerous small cysts less than 20 mm in diameter Type III (5%) has no cysts but is a solid mass of adenomatoid hyperplasia or bronchial structures

Congenital Cystic Adenomatoid Malformation

Congenital Cystic Adenomatoid Malformation

Congenital Cystic Adenomatoid Malformation Some lesions regress, as noted earlier, complicating the decision about intervening Regression has been noted both antenatally by ultrasonography and in the fi rst few months after birth

Congenital Cystic Adenomatoid Malformation The malignancies reported in association with CCAM include pleuropulmonary blastoma, rhabdomyosarcoma, squamous cell carcinoma and bronchioloalveolar carcinoma. Bronchioloalveolar carcinoma is the most common neoplasm to arise in a CCAM, and it almost always occurs in Stocker type I lesions.

Congenital Cystic Adenomatoid Malformation Prenatal treatment of CCAM includes resection and drainage of the cysts Drainage of cysts prenatally, using a pleuroamniotic shunt, may be performed if the mass is compromising contralateral lung development or causing hydrops The mortality rate for this intervention is approximately 30% for the fetus

Congenital Cystic Adenomatoid Malformation

Sequestration Pulmonary sequestration is typically separated into two types extralobar and intralobar

The common element in these two distinct pulmonary lesions is: Sequestration The common element in these two distinct pulmonary lesions is: absence of communication with the tracheobronchial tree and pulmonary arterial vasculature

Extralobar sequestration: mass of abnormal lung tissue that is completely separate from the remaining lung and has its own pleural investment

Sequestration

Sequestration

Sequestration

Sequestration Intralobar sequestration is considered a congenital lesion The diagnostic features are abnormal pulmonary tissue with no direct bronchial communication and a systemic arterial supply

Bronchogenic Cysts

PULMONARY ARTERIOVENOUS MALFORMATIONS an abnormal connection between a pulmonary artery and vein that bypasses the alveolocapillary complex right-to-left shunting and, subsequently, a varying degree of cyanosis

Take home messages Many of these lung lesions can be diagnosed in utero. For some large cystic lung lesions it is possible to intervene prenatally The clinical presentation of these congenital lesions varies considerably, from a neonate in extremis to an asymptomatic adult. Resection of the affected portion of the lung nearly always will be necessary. Long-term results are generally very good.