The Foetal Lung. Educational Exhibit Authors:

Transcription

1 The Foetal Lung Poster No.: C-1649 Congress: ECR 2015 Type: Educational Exhibit Authors: V. B. Pai, R. N. Chaubal, N. G. Chaubal, B. Pai ; Navi Mumbai/ IN, Thane/IN, Mumbai/IN Keywords: Foetal imaging, Ultrasound, Intrauterine diagnosis, Congenital DOI: /ecr2015/C-1649 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 24

2 Learning objectives The four chamber view is the most vital cross section studied during an examination for cardiac anomalies. This view helps to determine accurately any structural abnormality of the fortal heart. On the four-chamber view the heart occupies 25%-30% of the thoracic volume and is positioned in the left anterior quadrant, just to the left of the midline. The rest of the thorax is occupied but the lung parenchyma. At US, the fetal lungs normally appear homogeneous and are slightly more echogenic than the liver. The echogenicity of the lung increases as gestation advances. The axis of the heart is determined relative to the interventricular septum, which makes an angle of 45 with the midline. cardiomediastinal shift may often be the first clue to the presence of a unilateral chest mass or diaphragmatic hernia. Hence, the four-chamber view of the heart is an important landmark in the fetal chest and should be visualized in all fetuses during the 2nd and 3rd trimesters as part of routine obstetric imaging Page 2 of 24

3 Images for this section: Fig. 1: Transverse ultrasound image of a normal foetal thorax demonstrates homogeneous and symmetrical echogenicity of both the lungs. Dr. Nitin Chaubal, Thane Ultrasound Centre Page 3 of 24

4 Fig. 2: Transverse ultrasound of a normal foetal thorax demonstrating the normal cardiac axis and the relation of the heart with the adjacent lung parenchyma. The inter-ventricular septum (dotted line) is at an angle of 45 degrees with the midline Radiology, Padmashree Dr. D. Y. Patil Hospital and Research Centre - Navi Mumbai/IN Page 4 of 24

5 Background Abnormalities of the thorax are increasingly being recognized antenatally. The most commonly encountered anomalies can be classified into three broad categories: (1) Bronchopulmonary (lung bud) anomalies Bronchopulmonary anomalies include lung agenesis-hypoplasia complex (pulmonary underdevelopment), congenital pulmonary airway malformations (CPAMs), CLO, bronchial atresia, and bronchogenic cysts. (2) Vascular anomalies Vascular anomalies include absence of the main pulmonary artery, anomalous origin of the left pulmonary artery or pulmonary sling, anomalous pulmonary venous drainage, and pulmonary arteriovenous malformations. (3) Combined lung and vascular anomalies Combined lung and vascular bronchopulmonary sequestration. anomalies include scimitar syndrome and Vascular abnormalities may accompany bronchopulmonary abnormalities in some cases: for example, pulmonary vascular abnormalities with pulmonary hypoplasia or agenesis, or a systemic arterial supply to a small cyst CPAM ("hybrid" lesion). This poster is targetted towards lung bud anomalies and approachin a cardiomediastinal shift more accurately. Prior to understanding mediastinal shift understanding the anomalies and the nomenclature used of the foetal cardiac axis is of utmost importance. Dextrocardia - heart located in the right chest Dextroposition -heart in right chest with apex medial or to the left commonly due to extrinsic factors Dextroversion - heart in right chest with axis pointing to right,found in situs inversus & situs ambiguous Mesocardia - central position of the heart Page 5 of 24

6 Levocardia - left sided position of heart Levoposition - heart displaced further towards left Page 6 of 24

7 Images for this section: Fig. 3: Approaching causes of a cardio-mediatinal shift Dr. Ria V. Shetty, Mumbai, India Page 7 of 24

8 Findings and procedure details 1) PULMONARY UNDERDEVELOPEMENT Pulmonary underdevelopment has been classified into three categories a) Pulmonary agenesis: Complete absence of parenchyma, bronchus and vasculature b) Pulmonary aplasia: Blind ending rudimentary bbronchus is present, without lung parenchyma or vasculature c) Pulmonary hypoplasia: Bronchus and rudimentary lung is present: however the airway, alveoli and pulmonary vessels are decreased in size and number. Pulmonary agenesis and aplasia (Fig 4 and Fig 5) Abnormal blood flow in the dorsal aortic arch during the 4th week of gestation (embryonic phase) may cause pulmonary agenesis. Unilateral pulmonary agenesis is difficult to diagnose with prenatal US; however, it can be suspected on the basis of mediastinal shift. More than 50% of affected fetuses have other abnormalities involving the cardiovascular (patent ductus arteriosus, patent foramen ovale), gastrointestinal (tracheoesophageal fistula, imperforate anus), genitourinary, or skeletal (limb anomalies, vertebral segmentation anomalies) system. Imaging findings in pulmonary aplasia and agenesis are similar, except for the presence of a short blind-ending bronchus in aplasia. Pulmonary hypoplasia (Fig 6) It can be primary or secondary. Primary pulmonary hypoplasia, in which a cause cannot be elucidated, is much less common than secondary hypoplasia. The majority of cases of pulmonary hypoplasia are secondary to a process limiting the thoracic space for lung development, which can be either intra-thoracic or extra-thoracic. Page 8 of 24

9 The most common intra-thoracic cause is congenital diaphragmatic hernia, which is left sided in 75%-90% of cases, right sided in 10%, and bilateral in 5%. Left-sided congenital diaphragmatic hernia is relatively easier to detect due to the presence of an identifiable fluid-filled stomach in the thorax. In right-sided congenital diaphragmatic hernia, the liver herniates into the chest, which may be difficult to detect due to the solid echotexture of the liver. Color Doppler imaging may be helpful in identifying the portal and hepatic veins. Other intra-thoracic causes of pulmonary hypoplasia include CPAM, broncho-pulmonary sequestration, a cardiac or mediastinal mass, lymphatic malformation, and agenesis of the diaphragm. 2) CONGENITAL PULMONARY ADENOMATOID MALFORMATION (Fig 7-9) CPAMs are a heterogeneous group of cystic and noncystic lung lesions that largely result from early airway maldevelopment. The term congenital pulmonary airway malformation has been recommended as being preferable to the term congenital cystic adenomatoid malformation, CPAMs have been classified pathologically by Stocker according to cyst size and histologic resemblance to segments of the developing bronchial tree and airspaces. The newer classification scheme includes five types and is an extension of the original scheme (three types). (1) Type 0 has a tracheal or bronchial origin and is really acinar dysgenesis or dysplasia, (2) Type 1 has a bronchial or bronchiolar origin (large [2-10-cm] cyst lesion), (3) Type 2 has a bronchiolar origin (small [0.5-2-cm] cyst lesion), (4) Type 3 has a bronchiolar-alveolar duct origin (adenomatoid type), and (5) Type 4 has a distal acinar origin (the "unlined" cyst lesion). Page 9 of 24

10 Only three types of CPAMs are distinguished at imaging: 1.Large cyst CPAM (type I) and 2.Small cyst CPAM (type II) these two constitute Macrocystic CPAMs; and 3.Microcystic or solid type (type III) lesions, which have cysts that are smaller than 5 mm in diameter, with no discernible cystic spaces. Type 4 (per Stocker) usually appears as the large cyst type at imaging and is indistinguishable from a predominantly cystic pleuro-pulmonary blastoma. A CPAM may communicate with the proximal airways, although this communication is abnormal. Most CPAMs derive their blood supply from the pulmonary artery and drain via the pulmonary veins, with the exception of hybrid lesions, which can have a systemic blood supply. Fetal US of a large cyst CPAM demonstrates numerous variable-sized anechoic spaces intermixed with echogenic soft tissue. At prenatal US, A small cyst CPAM is identified as an echogenic mass with multiple small cysts. Indicators of a poor prognosis include large lesions, bilateral lung involvement, and hydrops. Quantitative measurements of mass size that help predict development of hydrops and poor outcome include a mass-thorax ratio of more than 0.56 or a CPAM volume ratio (i.e., volume of the mass divided by head circumference) greater than 1.6 3) BRONCHOGENIC CYSTS Bronchogenic cysts are part of the spectrum of foregut duplication cysts and are developmental lesions resulting from abnormal ventral budding of the tracheobronchial tree, probably occurring between the 26th and 40th days of fetal life. They are mostly situated in the mediastinum, typically near the carina. Less commonly, they may occur within the lung parenchyma, pleura, or diaphragm. Page 10 of 24

11 At prenatal US, bronchogenic cysts manifest as unilocular fluid-filled cysts in the middle or posterior mediastinum. The differential diagnosis includes esophageal duplication cysts and neurenteric cysts. Esophageal duplication cysts are generally located in the middle or posterior mediastinum. Neurenteric cysts are located in the posterior mediastinum, may demonstrate communication with the spinal canal, and are invariably associated with vertebral defects in the region of this communication. 4) CONGENITAL HIGH AIRWAY OBSTRUCTION SYNDROME (Fig 10) Congenital high airway obstruction syndrome is a rare congenital anomaly caused by laryngeal or tracheal atresia, tracheal stenosis or web, or, rarely, compression from a double aortic arch. There is outflow obstruction of the fetal lung fluid, which leads to pulmonary hyperplasia. Prenatal US findings include symmetrically enlarged echogenic lungs, dilated and fluidfilled trachea and bronchi, and inverted hemidiaphragms. The heart appears small compared with the enlarged lungs and appears somewhat anteriorly positioned in the chest due to compression by the lungs. Hydrops may be present. 5) PULMONARY SEQUESTRATION (Fig 11 - Fig 12) Pulmonary sequestration is the second most common lung lesion (after CPAM) detected antenatally. It is characterized by a portion of lung that does not connect to the tracheobronchial tree and has a systemic arterial supply, usually from the thoracic or abdominal aorta. Occasionally, the systemic arterial supply originates from the celiac or splenic artery or from the intercostal, subclavian, or even coronary arteries. Two types of sequestration have been described: intralobar and extralobar. Page 11 of 24

12 The extralobar form has its own pleural investment and systemic venous drainage, whereas the intralobar form shares the pleural investment with the normal lung and usually (but not invariably) drains into the pulmonary venous system. It arises from a supernumerary lung bud caudad to the normal lung bud. If the lung bud arises before the development of the pleura, it is invested with adjacent lung and becomes an intralobar sequestration. If the lung bud arises after pleura formation, it grows separately and acquires its own pleural covering. The extralobar form is most commonly diagnosed in the prenatal-neonatal period, whereas the intralobar form is usually diagnosed later in childhood or adulthood. Extralobar sequestration may be associated with other congenital systemic anomalies, such as congenital diaphragmatic hernia, cardiac abnormalities, pulmonary hypoplasia, or foregut duplication cysts. It may be located below the diaphragm and may mimic a neuroblastoma or adrenal hemorrhage. There is considerable controversy over the cause of intralobar sequestration. Because these lesions were previously diagnosed in older children and show pathologic evidence of chronic inflammation, it has been suggested that repeated lung inflammation could cause small, normally present systemic pulmonary ligament vessels to hypertrophy, producing an acquired intralobar sequestration. It is not definitely known if the underlying lung was normal or abnormal to begin with. It seems likely that intralobar sequestration is an infected congenital lesion that manifests because of this infection, since with the wider availability of prenatal imaging an increasing number of intralobar sequestrations are being diagnosed prenatally. At prenatal US, extralobar pulmonary sequestration is seen as a homogeneous hyperechoic mass in a paraspinal location, most often the left lower thorax. The feeding artery originating from the descending aorta may be seen at color Doppler US. Occasionally, these vessels may not be identified at Doppler US, making extralobar sequestration indistinguishable from a microcystic CPAM. Large lesions can compress the esophagus and thoracic veins and subsequently cause hydrops, which is an indication for fetal intervention or early delivery. Page 12 of 24

13 Images for this section: Fig. 4: A cardio-medistinal shift with no obvious right lung parenchyma suggestive of pulmonary agenesis / aplasia Dr. Nitin Chaubal, Thane Ultrasound Centre Page 13 of 24

14 Fig. 5: Autopsy specimen of the foetus confirming the diagnosis of right pulmonary agenesis Dr. Nitin Chaubal, Thane Ultrasound Centre Page 14 of 24

15 Fig. 6: Intra-thoracic position of the fundic bubble (ST), a cause of secondary pulmonary hypoplasia with consequent cardio-mediastinal shift Dr. Nitin Chaubal, Thane Ultrasound Centre Page 15 of 24

16 Fig. 7: Type I CPAM (Macrocystic) Dr Nitin Chaubal, Thane Ultrasound Centre, India Page 16 of 24

17 Fig. 8: Typer II CPAM (Cysts < 1 cm) Dr Nitin Chaubal, Thane Ultrasound Centre, India Page 17 of 24

18 Fig. 9: Type III CPAM Dr Nitin Chaubal, Thane Ultrasound Centre, India Page 18 of 24

19 Fig. 10: Both the lungs appear enlarged with increased echogenicity and mesocardia Dr Nitin Chaubal, Thane Ultrasound Centre, India Page 19 of 24

20 Fig. 11: A homogeneous triangular mass is noted in the subdiaphragmatic region. Dr. Nitin Chaubal, Thane Ultrasound Centre Page 20 of 24

21 Fig. 12: The vascular supply is seen to arise from the aorta. Findings are suggestive of Extralobar Pulmonary Sequestration. Dr. Nitin Chaubal, Thane Ultrasound Centre Page 21 of 24

22 Conclusion The four chamber view if the heart, is perhaps the most important view during an examination of the fortal thorax. Pathologies of the lung characteritically tend to have either a 'pull' or a 'push' effect on the mediastinum. Any anomaly seen in the position of the heart must inspire a careful examination of the lungs too. Page 22 of 24

23 Personal information Dr. Vivek B. Pai IInd Year Resident Department of Radiodiagnosis Padmashree Dr. D.Y.Patil Hospital and Research Centre Nerul(E), Navi Mumbai, India Page 23 of 24

24 References Goldstein RB. A practical approach to fetal chest masses. Ultrasound Q 2006;22(3): Newman B. Congenital bronchopulmonary foregut malformations: concepts and controversies. Pediatr Radiol 2006;36(8): Langston C. New concepts in the pathology of congenital lung malformations. Semin Pediatr Surg 2003;12(1): Moore KL, Persaud TVN. The developing human: clinically oriented embryology. 7th ed. Philadelphia, Pa: Saunders, 2002 Skandalakis JE, Gray SW, Symbas P. The trachea and the lung. In:, Skandalakis JE, Gray SW, eds. Embryology for surgeons. 3rd ed. Baltimore, Md: Williams & Wilkins, 1994; Rypens F, Metens T, Rocourt N, et al.. Fetal lung volume: estimation at MR imaging-initial results. Radiology 2001;219(1): Chitkara U, Rosenberg J, Chervenak FA, et al.. Prenatal sonographic assessment of the fetal thorax: normal values. Am J Obstet Gynecol 1987;156(5): Biyyam DR, Dighe MK, Siebert JR. Antenatal diagnosis of intestinal malrotation on fetal MRI. Pediatr Radiol 2009;39(8): Quinn TM, Hubbard AM, Adzick NS. Prenatal magnetic resonance imaging enhances fetal diagnosis. J Pediatr Surg 1998;33(4): Stocker JT. Congenital pulmonary airway malformation: a new name for and an expanded classification of congenital cystic adenomatoid malformation of the lung. Symposium 24: non-neoplastic lung disease. Histopathology 2002;41(suppl 2): Davenport M, Warne SA, Cacciaguerra S, Patel S, Greenough A, Nicolaides K. Current outcome of antenally diagnosed cystic lung disease. J Pediatr Surg 2004;39(4): Kuhn C, West WW, Craighead JE. Lungs. In:, Damjanov I, Linder J, eds. Anderson's pathology. 10th ed. St Louis, Mo: Mosby, 1996;1471. Laurin S, Hägerstrand I. Intralobar bronchopulmonary sequestration in the newborn: a congenital malformation. Pediatr Radiol 1999;29(3): McAdams HP, Kirejczyk WM, Rosado-de-Christenson ML, Matsumoto S. Bronchogenic cyst: imaging features with clinical and histopathologic correlation. Radiology 2000;217(2): Page 24 of 24