Lower respiratory tract congenital malformations Notes

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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

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Lower respiratory tract congenital malformations essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Lower respiratory tract congenital malformations by visiting the associated Learn Page.