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B. Neonatal stage
· Precursors of typical acinar unit are present at birth: bronchioles, transitional ducts, and terminal saccule
· Alveolar development continues after birth with remodeling and multiplication
· The total adult number of alveoli are not reached until at least age 8
· Alveolar enlargement continues until adulthood, although no new alveoli are added
C. Histology
· The mature lung is characterized by closely packed alveoli divided by thin septa, occupied by capillaries
· Capillary endothelium is typically a single cell layer with few organelles and thin cytoplasmic matrix
· Over 95% of alveolar epithelium is type I cells, which are also very thin with few organelles
· Type II alveolar cells are cuboidal and secrete surfactant
· Surfactant synthesis peaks at term and decreases to adult levels shortly thereafter
· An increase in the lecithin-sphingomyelin ratio to more than 2:1 occurs just before birth
· Type II cells can be stimulated to produce this pattern of phospholipid by steroids, thyroxine, estrogens, beta-agonists, and increases in ventilation or tidal volume
· Surfactant stabilizes the alveoli, lowers surface tension to keep alveoli open at low volumes, prevents alveolar wall adhesion, and helps maintain pulmonary compliance
B. Hypoplasia
· Failure to obtain adequate size; all components are present, but incompletely developed
· Severity of hypoplasia determines the degree of respiratory compromise
· Major abnormality is a decrease in the number of airway generations and pulmonary artery branchings
· Two general causes: large diaphragmatic hernia or primary embryologic defect
· Hernia interferes with alveolar development during last 2 months of intrauterine growth
· Embryologic defects occur early and may be associated with other syndromes
· Associated anomalies include oligohydramnios, prune-belly syndrome, Potter's syndrome, and scimitar syndrome
· If associated with diaphragmatic hernia, the hypoplastic lung should not be removed at surgery, as it will recover some function with time
A. Pathogenesis
· Accounts for about 50% of all congenital lung malformations
· Intrinsic causes: bronchomalacia due to abnormal cartilaginous support, mucus plugging, bronchial torsion, redundant mucosa, foreign body aspiration
· Extrinsic causes: bronchial compression from pulmonary artery sling, great vessel aneurysms, enlarged cardiac chambers
· Pulmonary hypoplasia: decreased number of alveoli become overdistended due to air trapping
· Alveolar hyperplasia: excessive number of alveoli overexpanded a polyalveolar lobe
· Most common in LUL, then RUL, then RML
B. Symptoms
· Respiratory distress occurs in 50% of patients in the first week of life (50%)
· 80% of infants will be symptomatic by 6 months of age
· Most common symptoms are tachypnea, cough, cyanosis, and dyspnea
· Pulmonary infection in the affected lobe occurs most commonly between 1 and 6 months of age
· Presentation is uncommon after age 6 months
· Physical findings include hyperresonance and decreased breath sounds on the affected side
· CXR shows hyperlucency on the affected side and mediastinal shift to the opposite side
· Air bronchography demonstrates bronchial wall collapse with expiration if bronchomalacia is the cause
C. Treatment
· Indication for surgery is life-threatening progressive insufficiency from normal lung compression
· Careful induction of anesthesia and positive pressure ventilation
· Immediate thoracotomy necessary in the critically ill infant, as ventilation may worsen normal lung compression by rapidly expanding the affected lung
· Surrounding atelectatic normal lung tissue should be preserved
· Lobectomy should result in cure
· Long-term outlook is good with relatively normal PFT's
A. Pathology
· Congenital cysts are typically unilocular and confined to a single lobe; the lower lobes are more commonly involved
· Congenital cysts that persist for more than 1 year are unlikely to resolve spontaneously
· Multiple cysts are rarely congenital and are probably acquired; causes include staphylococcal pneumonia and cystic fibrosis.
· Multiple cysts may fluctuate in size and can develop rapidly
· CXR usually adequate for identification
B. Symptoms
· Expansion results in respiratory distress
· Infection causes fever, cough, and sepsis
C. Treatment
· Solitary congenital cysts can be treated with cystectomy or lobectomy if necessary
· Infected solitary cysts should be treated with antibiotics and resected when quiescent
· Multiple cysts should be treated as part of underlying systemic disease; surgical intervention is rarely required and is contraindicated for pneumatoceles
· Chest tube placement or aspiration for diagnosis is discouraged for tension cysts, as this can result in empyema
A. Pathology
· Typically confined to a single lobe
· Progressive air trapping in cystic areas leads to over distension of involved lobe
· Three subtypes (see table)
· High incidence of associated congenital anomalies and death with type II
| Type I | Type II | Type III | |
| Morphology | Multiple large cysts or single large cyst | Multiple, evenly spaced cysts not over 1.2 cm | Multiple small cysts less than 0.5 cm |
| Contents | Air of fluid | Air | Solid |
| Wall | Smooth muscle and connective tissue | Terminal bronchioles | Adenomatoid hyperplasia or bronchial |
| CXR | Unilateral large cyst or homogenous mass, may have mediastinal shift and air-fluid level | Smaller nonhomogenous cyst | Homogenous mass |
B. Symptoms
· Progressive respiratory distress in a newborn infant
· Tachypnea, subcostal retraction, cyanosis
· Older child - chronic pulmonary infection
· Differential should include congenital diaphragmatic hernia, and barium swallow will differentiate the two
C. Treatment
· Identification of the lesion is the indication for surgery, with or without symptoms
· Lobectomy is usually adequate
· Attempt at segmentectomy is usually met with prolonged air leak and complications
A. Pathology
· Cysts can occur either in the parenchyma (70%) or the mediastinum (30%)
· The most common locations are paratracheal, carinal, hilar, and paraesophageal
· Generally round and unilocular
· Lined with ciliated columnar epithelium
· Most do not communicate with the tracheobronchial tree
· Can mimic lobar emphysema from bronchial obstruction
· Can become secondarily infected
B. Symptoms
· Most common presentation in the neonate is progressive dyspnea, wheezing, stridor, and cyanosis
· Obstructive symptoms occur most commonly in infants less than 1 year of age
· Paratracheal, carinal, and hilar cysts are commonly asymptomatic
· Communicating cysts are almost always symptomatic: productive cough, fever, hemoptysis
· CXR shows homogenous, sharply delineated cyst; air/fluid levels may be present in communicating cyst
· CT is the test of choice for diagnosis and anatomic delineation
C. Treatment
· Indications for surgery include increasing cyst size, air/fluid level, symptomatic cyst, and subcarinal cyst
· Small, asymptomatic cysts can be followed with interval CXR
· Cyst excision with sparing of surrounding pulmonary tissue is the treatment of choice
A. Pathology
· Unicystic or polycystic parenchyma with extensive fibrosis and vascular sclerosis
· Arterial supply is usually from the thoracic aorta (75%) or abdominal aorta (20%)
· Venous drainage is usually to the pulmonary veins
· Right-sided lesions more often have other venous drainage
· Much more frequent than extralobar type
B. Symptoms
· Recurrent episodes of infection in older children and adolescents
· CXR shows cystic structure with or without air-fluid level
· CT is procedure of choice; aortography and barium swallow may be necessary for anatomy
C. Treatment
· Identification of the lesion is indication for surgery
· Careful ligation of the anomalous artery followed by resection
· Prevents long-term infection and possible neoplastic changes
A. Pathology
· Mass of loose, spongy parenchyma with multiple small cysts and dilated bronchioles and ducts
· Arterial supply is also usually from the thoracic or abdominal aorta
· Venous drainage is usually to the azygous or hemiazygous system
· More common on the left side and usually found between the lower lobe and the diaphragm
B. Symptoms
· Most present in neonatal period due to respiratory distress
· CXR shows triangular homogenous mass with apex pointing toward hilum
· CT may provide additional localization, but vessels often too small to identify
C. Treatment
· Identification of the lesion is indication for surgery
· Careful ligation of the anomalous artery followed by resection
· As with intralobar sequestration, resection prevents long-term infection and possible neoplastic changes
| ILS | ELS | |
| Gender predominance | Equal | Male |
| Location predominance | Left | Left |
| Pleural investment | No | Yes |
| Arterial supply | Thoracic/abdominal aorta | Thoracic/abdominal aorta |
| Venous drainage | Pulmonary | Azygous/hemiazygous |
| Other anomalies | Rare | Common |
| Age at diagnosis | Adolescent/young adult | Neonate |
| Symptoms | Cough, fever | Respiratory distress |