Lower respiratory tract congenital malformations Notes

NOTES NOTES LOWER RESPIRATORY TRACT CONGENITAL MALFORMATIONS GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES DIAGNOSIS Prenatal ultrasound, radiography, CT scan, MRI ▪ Structural anomalies of lung during embryonic development TREATMENT SIGNS & SYMPTOMS ▪ Surgical resection, respiratory support ▪ Asymptomatic/respiratory distress CONGENITAL PULMONARY AIRWAY MALFORMATION osms.it/cpam PATHOLOGY & CAUSES ▪ Congenital pulmonary airway malformation (CPAM) ▪ AKA congenital cystic adenomatoid disorder → part of/entire lung lobe replaced by non-functional cysts ▪ Result of abnormalities in branching morphogenesis of lung ▪ Rare in general; most common congenital lung malformation TYPES ▪ CPAM Type 0: rare; multiple small cysts composed of cartilage, mucus cells; lethal anomaly ▪ CPAM Type 1: most common; large (> 2cm/0.78in) multiloculated cysts; good prognosis ▪ CPAM Type 2: small uniform cysts; 874 OSMOSIS.ORG associated with other congenital malformations (e.g. esophageal atresia with esophageal fistula); poor prognosis ▪ CPAM Type 3: large; not true cysts; communicates with surrounding parenchyma; “adenomatoid” type; more common in individuals who are biologically male ▪ CPAM Type 4: rare CAUSES ▪ Possibly, in utero airway obstruction/atresia; definitive cause unknown RISK FACTORS ▪ Occurs sporadically ▪ Not related to maternal factors ▪ No genetic predisposition except Type 4 (associated with familial pleuropulmonary blastoma syndrome)

Chapter 124 Lower Respiratory Tract Congenital Malformations COMPLICATIONS ▪ Pulmonary hypoplasia ▪ Mediastinal shift, putting pressure against heart ▪ Respiratory infections ▪ Rapid growth → venous outflow obstruction, cardiac failure, hydrops fetalis, death ▪ Longstanding CPAMs → cancer diaphragm, absence of visible lung tissue MRI/CT scan ▪ Delineate pathology TREATMENT SURGERY ▪ Minimally invasive surgical resection (thoracoscopy) SIGNS & SYMPTOMS ▪ Large cysts: in utero placement of Harrison thoracoamniotic shunt ▪ 75% of individuals: asymptomatic ▪ 25% of individuals: cyanosis, pneumothorax, respiratory distress, tachypnea, intercostal retractions, grunting ▪ Hyperresonance on percussion, diminished vesicular murmur, asymmetrical thorax ▪ Rare: fetal surgery in utero; surgical delivery, ex utero intrapartum treatment (EXIT) procedure Figure 124.1 Illustration depicting continuous pulmonary airway malformation. Figure 124.2 A fetal MRI demonstrating a congenital pulmonary airway malformation. DIAGNOSIS ▪ Definitive diagnosis usually not possible without surgical resection, histopathological evaluation DIAGNOSTIC IMAGING Prenatal ultrasound ▪ Echogenic mass appearing in the chest, displacement of heart, flat/everted OSMOSIS.ORG 875

Figure 124.3 The histological appearance of a congenital cystic type II malformation. There are multiple small cystic spaces lined by immature respiratory tissue. Figure 124.4 A CT scan of the chest demonstrating a pulmonary congenital cystic adenomatoid malformation, Type I, presenting as a single cyst of middle lobe in an adult. PULMONARY HYPOPLASIA osms.it/pulmonary_hypoplasia PATHOLOGY & CAUSES ▪ Underdevelopment of lungs → low number/ size of bronchopulmonary segments/alveoli ▪ Typically occurs prior to/after pseudoglandular stage (6–16 weeks gestation) TYPES ▪ Primary ▫ Idiopathic, not associated with maternal/ fetal abnormalities; rare ▪ Secondary ▫ Due to fetal abnormalities disrupting lung development ▫ Associated with bilateral renal agenesis, congenital diaphragmatic hernia, congenital cystic adenomatoid malformation, fetal hydronephrosis, 876 OSMOSIS.ORG caudal regression syndrome, mediastinal tumor, dextrocardia, sacrococcygeal teratoma ▫ Bilateral renal agenesis → oligohydramnios → decreased lung expansion, decreased mechanical stretching → decreased growth factors lung synthesis → pulmonary hypoplasia RISK FACTORS ▪ Decreased amniotic fluid: severe oligohydramnios, mid-trimester rupture of membranes ▪ Disruption of signaling pathways involved in growth: sonic hedgehog (SHH) signaling pathway ▪ Aberrant expression growth factors: vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), fibroblast growth factor (FGF) ▪ Early delivery

Chapter 124 Lower Respiratory Tract Congenital Malformations COMPLICATIONS ▪ Respiratory distress, chronic respiratory failure, bronchopulmonary dysplasia, pneumothorax, secondary scoliosis, impaired cardiac function ▪ Survival depends on degree of hypoplasia, cause of restricted growth SIGNS & SYMPTOMS ▪ Prenatal: poor fetal movement, amniotic fluid leakage, oligohydramnios ▪ Postnatal: asymptomatic/severe respiratory distress, apnea, cyanosis ▪ Small, bell-shaped chest; heart displacement; decreased/absent breath sounds TREATMENT OTHER INTERVENTIONS ▪ Amnioinfusion: instilling isotonic fluid into amniotic cavity ▪ Amniopatch: intra-amniotic injection of platelets, cryoprecipitate → seal amniotic fluid leak ▪ Treatment of underlying condition; respiratory support; in severe cases, fetal surgery DIAGNOSIS DIAGNOSTIC IMAGING 3D ultrasound ▪ Total lung volume measurement Doppler ultrasound/magnetic resonance angiography ▪ Shows lack of blood supply CT scan/MRI ▪ Shows loss of lung volume Radiography Figure 124.5 A chest X-ray demonstrating a volume defect of the right thoracic cavity caused by pulmonary hypoplasia. LAB RESULTS ▪ Renal function (serum creatinine, blood urea, electrolyte levels) ▫ Oligohydramnios OTHER DIAGNOSTICS ▪ Lung weight, lung weight to body weight ratio, mean radial alveolar count (RAC), lung DNA OSMOSIS.ORG 877