Fetal Bronchopulmonary Sequestration

• Objectives

  After completing this course, the participant should be able to:

  • Discuss the pathophysiology of an extralobar and intralobar pulmonary bronchopulmonary sequestration.
  • Understand the differences between an intralobar and extralobar pulmonary sequestration.
  • Identify the sonographic signs associated with bronchopulmonary sequestration.
  • Review and be able to delineate the differences between other diagnoses that are frequently confused with a bronchopulmonary sequestration.

• Faculty

  Lyndon M. Hill, MD
  Professor Obstetrics, Gynecology and Reproductive Sciences
  Medical Director Ultrasound
  Magee-Womens Hospital of UPMC
  

• Accreditation

  The Institute for Advanced Medical Education is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

  The Institute for Advanced Medical Education designates this enduring material for a maximum of 1 AMA PRA Category 1 Credit™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

  These credits are accepted by the American Registry for Diagnostic Medical Sonography (ARDMS).

  For information on applicability and acceptance of continuing education credit for this activity, please consult your professional licensing board or other credentialing organization.

• Target Audience

  Physicians, sonographers and others who perform and/or interpret ultrasound.

• System Requirements

  In order to complete this program you must have a computer with a recent browser version. You must also have the capability to display and print PDF files in order to view and print out your certificate. (Note: Your CME certificate is stored in your account and is available at any time.)

  For any questions or problems concerning this program or for problems related to the printing of the certificate, please contact IAME at 802-824-4433 or info@iame.com .

• Instructions for Participation and Credit

  This activity is designed to be completed within the time designated. To successfully earn credit, participants must complete the activity during the valid credit period. To receive AMA PRA Category 1 Credit™, you must receive a minimum score of 70% on the post-test.

  Follow these steps to earn CME credit:

  • Read the target audience, learning objectives, and author disclosures.
  • Study the educational content online or printed out.
  • Take the CME quiz. Choose the best answer to each test question. To receive a certificate, you must receive a passing score of 70%. We encourage you to complete the Activity Evaluation to provide feedback for future programming.

  Your CME credits will be archived in the account you create and can be accessed at any time.
  
  

  Estimated Time for Completion: approximately 1 hour
  Date of Release and Review: February 15, 2014, January 15, 2017
  Expiration Date: January 31, 2020
  Program: 1106

• Disclosure

  In compliance with the Essentials and Standards of the ACCME, the author of this CME tutorial is required to disclose any significant financial or other relationships they may have with commercial interests.

  Dr. Lyndon Hill discloses no relevant financial interests with commercial interests.

  No one at IAME who had control over the planning or content of this activity has relationships with commercial interests.

• The Course

  "Sequestration" is from Latin, meaning to separate. Bronchopulmonary sequestration is divided into intralobar and extralobar. Both intralobar (ILS) and extralobar (ELS) sequestrations are separated from the normally developed bronchopulmonary tree. Embryologically, sequestrations arise from a supernumerary lung bud. If the lung bud develops before the pleura, it becomes intralobar in origin. If the lung bud develops after the pleura, it becomes extralobar in origin (Fig. 1)¹. Hence, extralobar sequestrations have their own visceral pleura.

  Figure 1. Bronchopulmonary sequestration.

  Some cases of ILS are acquired due to bronchial obstruction, distal infection, and recruitment of a systemic arterial blood supply. Small systemic arteries arising from the thoracic aorta traverse the pulmonary ligament to supply the lower lobes of the lung. These vessels are distinct from the pulmonary circulation. If the normal pulmonary arterial supply is compromised, it has been proposed that these smaller vessels are parasitized to supply the infected portion of a lower lobe. This proposed mechanism explains some of the distinct characteristics of intralobar, in contrast to extralobar, sequestrations; i.e., an absence of congenital anomalies; and the venous drainage of ILS into the pulmonary veins².

  Rare cases of bilateral intralobar or coexistent intralobar and extralobar sequestrations represent an anomaly of embryonic development rather than an acquired lesion³.

  The original embryologic connection between a pulmonary sequestration and the foregut involutes. Occasionally, it persists, allowing communication with the gastrointestinal tract in isolated cases of sequestration^4,5.

  Bronchopulmonary sequestrations represent up to 23% of prenatally detected lung lesions⁶.

  ELS have an aberrant systemic pulmonary drainage. 75% of venous drainage is through the vena cava or azygous system and 2% drain via the pulmonary veins.

  In 80% of extralobar pulmonary sequestrations the arterial blood supply is a single vessel, usually derived from the thoracic or abdominal aorta (Fig. 2)⁷. Other atypical sources of blood supply include the celiac trunk, left gastric, subclavian, and intercostals¹

  Figure 2. Left lower lobe pulmonary sequestration (markers) with an aberrant feeding vessel (arrow).

  The feeding vessel to an ELS may come off the aorta at any angle. As a result, the vascular supply is not always identified prenatally⁸. Three-dimensional power Doppler has been utilized to improve the detection of an aberrant feeding vessel to a bronchopulmonary sequestration⁹. The diameter of the arterial feeding vessel is between 1 and 12 mm¹⁰. Aneurysms of the aberrant vessel with rupture and subsequent hemothorax have been described¹¹.

  Since the blood supply to ILS and ELS overlap, they cannot generally be distinguished antenatally.

  ELS occur more commonly in males (4:1) and 80-90% occur in the base of the left lung (Fig. 3)⁷. ILS are 75% of all sequestrations, do not have a gender preference, and 60% are left posterior basal in location¹².

  Figure 3. Left bronchopulmonary sequestration (markers).

  There are only a few cases of prenatally diagnosed intralobar bronchopulmonary sequestions².

  Differential Diagnosis

  Congenital Pulmonary Airway Malformation

  Congenital pulmonary airway malformation (CPAM) is associated with ELS in 15% - 25% of cases^7,13. Microcystic congenital pulmonary airway malformation is difficult to distinguish from bronchopulmonary sequestration (Fig. 4). Pulmonary sequestrations account for up to 25% of chest masses that were thought prenatally to represent CPAMs².

  Figure 4. Congenital pulmonary airway malformation (arrow) with secondary hydrops resulting in ascites (curved arrow).

  A hybrid combination of a bronchopulmonary sequestration and CPAM are relatively common¹³. The presence of a large cyst with an echogenic left lung mass suggests a hybrid lesion. However, cysts of various sizes may be present in ILS¹⁰. Hybrid lesions have connections with both the systemic arterial and pulmonary supply. The detection of a feeding vessel to a lung lesion would, therefore, not exclude a combined lesion.

  Lobar Emphysema

  Congenital lobar emphysema (Fig. 5) is a second echogenic lung mass that is difficult to distinguish from bronchopulmonary sequestration. Postnatally, a diagnosis of congenital lumbar emphysema can be confirmed by computed tomography that shows emphysematous alveoli, in contrast to the distorted lung parenchyma of cystic pulmonary airway malformation¹⁴.

  Figure 5. Congenital lobar emphysema (arrow).

  Neuroblastoma

  A subdiaphragmatic fetal mass is frequently presumed to be a neuroblastoma. However, a subdiaphragmatic ELS occurs once for every 2.5 neuroblastomas¹⁵. A left-sided subdiaphragmatic mass that is detected in the 2nd or early 3rd trimester is most likely an ELS. A right-sided subdiaphragmatic mass detected at, or after, 30 weeks' gestation should presumptively be considered a neuroblastoma. A bronchopulmonary sequestration characteristically decreases in size over time, while the size of a neuroblastoma increases¹⁵

  Adrenal Hemorrhage

  An adrenal hemorrhage (Fig. 6) is the most common etiology for a suprarenal mass. It can be readily distinguished from extrapulmonary sequestration by its changing echo pattern over serial examinations¹⁶. Calcifications may eventually develop after a long-standing hemorrhage.

  Figure 6. Adrenal hemorrhage (markers).

  Mesoblastic Nephroma

  Mesoblastic nephroma (Fig. 7) is the most common renal tumor in the neonatal period. It occurs once in every 12,500 – 27,500 live births and accounts for 50% of neonatal tumors^17,18. Mesoblastic nephromas are homogeneously solid and should not, therefore, be confused with an extralobar pulmonary sequestration. They are characteristically associated with polyhydramnios – an uncommon sonographic finding with extrapulmonary sequestrations¹⁹.

  Figure 7. Mesoblastic nephroma (arrow).

  Nephroblastoma (Wilm's Tumor)

  A nephroblastoma is a renal carcinoma that typically occurs in children. It is rarely detected in-utero and always in the 3rd trimester²⁰.

  Sonographic Findings

  ELS is classically a diffusely echogenic mass in the base of the left lung. The shape of the mass either conforms to the lower lobe or is triangular (Fig. 8). While the majority of extralobar pulmonary sequestrations are small to medium in size, larger lesions will occasionally occur (Fig. 9). A bronchopulmonary sequestration is usually unilateral; bilateral cases have been reported²¹.

  Figure 8. Right bronchopulmonary sequestration (markers)

  

  Figure 9. Right bronchopulmonary sequestration (arrow)

  As with CPAM, ELS has not been diagnosed until after 16 weeks' gestation^22,23.

  Over 85% of ELS have dilated suprapleural lymphatic vessels that are responsible for the ipsilateral pleural effusion noted in some of these cases.

  The identification of a feeding vessel to the thoracic mass from the thoracic or abdominal aorta help to differentiate ELS from CPAM, or other echogenic lesions (Fig. 10).

  Figure 10. Bronchopulmonary sequestration with an aberrant blood supply (green arrow)

  Associated anomalies occur in over 50% of extrapulmonary sequestrations (Table I)^10,24. As previously stated, ILS is not associated with an increased risk of additional anomalies¹⁵. Extrapulmonary sequestrations are most frequently associated with congenital diaphragmatic hernia. Hence, a left-sided abdominal mass in a fetus with a diaphragmatic hernia should be considered an extrapulmonary sequestration until proven otherwise²⁵.

  Table I. Associated congenital anomalies with extralobar sequestrations.

  • Congenital heart disease
  • Diaphragmatic hernia
  • Eventration of the diaphragm
  • Accessory spleen
  • Gastric duplication

  A correct prenatal diagnosis of pulmonary sequestration is made approximately 29% of the time²⁶.

  Intra-thoracic pulmonary sequestrations are much more likely to have associated sonographic findings, i.e. polyhydramnios, pleural effusions, mediastinal shift, and hydrops. None of these sonographic findings are generally found with intra-abdominal pulmonary sequestrations²⁶.

  Complete resolution or regression of a fetal pulmonary sequestration may occur in up to 70% of cases. Postnatal CT has confirmed the resolution of antenatally diagnosed masses^5,27,28. However, some presumed bronchopulmonary sequestrations that appeared to resolve in-utero are detected on postnatal computed tomography. The reduction in size or disappearance of an in-utero bronchopulmonary sequestration is thought to be due to torsion and/or clotting of the vascular pedicle, or decompression into the normally expanding lung^15,29.

  The rate of hydrops with bronchopulmonary sequestration ranges from 7%²⁴ to 35%²⁶. The etiology of hydrops in bronchopulmonary sequestrations may be either from: 1) a mass effect; 2) a tension pneumothorax due to fluid secretion by the mass, resulting in cardiac compression and/or vena caval obstruction; or 3) large volume shunting through the systemic arterial feeder vessel to the mass.

  Fetal Management

  Once the diagnosis of bronchopulmonary sequestration has been made, the presence or absence of hydrops becomes the most important prognostic feature³⁰. While there are isolated case reports of survival after the sonographic detection of hydrops, this combination of findings is generally fatal³¹. Survival rates are significantly higher among hydropic fetuses with bronchopulmonary sequestration who have in-utero intervention³².

  The 6-10% of bronchopulmonary sequestrations with an isolated pleural effusion^5,28 can be managed with serial thoracentesis or a thoraco-amniotic shunt. Survival is improved after shunting^10,12. Complications associated with a shunt procedure include chest wall trauma, fetal hemorrhage, displacement or plugging of the catheter, placental abruption, preterm premature rupture of the membranes, preterm labor, and intrauterine demise^33,34.

  Since the development of a pleural effusion cannot be predicted, patients with a diagnosis of bronchopulmonary sequestration should be followed with serial ultrasound examinations until delivery.

  One approach to the treatment of a pulmonary sequestration with symptomatic pleural effusion is YAG laser coagulation of the feeding vessel²³.

  For fetuses > 32 weeks' gestation, delivery with immediate postnatal surgical resection should be considered in the presence of a presumptive bronchopulmonary sequestration and hydrops²⁸.

  In a recent series of 39 antenatally diagnosed bronchopulmonary sequestrations, regression was documented in 72% of cases; there was one prenatal mortality⁵. This success may not be reproduced in additional series with a lower prevalence of lesions that regress.

  Neonatal Management

  Large pleural effusions should be drained immediately. However, the timing of surgical resection is highly variable and dependent upon neonatal status. The resection of an extralobar lesion does not affect the amount of functioning lung tissue. Pre-operative evaluation of the arterial and venous supply is mandatory to avoid ligation of anomalous veins that may constitute the only drainage for the ipsilateral lung³⁵.

  If a bronchopulmonary sequestration has regressed in utero, a postnatal CT should be performed to confirm resolution. If a mass is still detected, management varies from prophylactic removal due to the theoretical risk of infection or hemorrhage, to observation with serial imaging³⁶. Surgical removal of an extrapulmonary sequestration may be by either open laparotomy or laparoscopy³⁷.

  References

  1. Devine PC, Malone FD. Non-cardiac thoracic masses. Clin Perinatol 2000;27:865-899.
  2. Vijayaraghavan SB, Rao PS, Selverasu CD, Rao TMS. Prenatal sonographic features of intralobar bronchopulmonary sequestration. J Ultrasound Med 2003;22:541-544.
  3. Frazier AA, de Christenson NOR, Stocker JT, Templeton PA. Intralobar sequestration: radiologic-pathologic correlation. Radiographics 1997;17:725-745.
  4. Dhingsa R, Coakley FV, Albanese CTR, Filly RA, Goldstein R. Prenatal sonography and MR imaging of pulmonary sequestration. AJR 2003;180:433-437.
  5. Gerle RD, Jaretzki A 3rd, Ashley CA, Berne AS. Congenital bronchopulmonary foregut malformation: pulmonary sequestration communicating with the gastrointestinal tract. N Engl J Med 1968;278:1413-1419.
  6. Adzick NS, Harrison MR, Crombleholme TM, Flake AW, Howell LJ. Fetal lung lesions: management and outcome. Am J Obstet Gynecol 1998;179:884-889.
  7. Stocker JT. Sequestrations of the lung. Semin Diagn Pathol 1986;3:106-121.
  8. Sepulveda W. Perinatal imaging in bronchopulmonary sequestration. J Ultrasound Med 2009;28:89-94.
  9. Ruano R, Benachi A, Aubry M-C, Revillon Y, Emond S, Dumez Y, Dommengues M. Prenatal diagnosis of pulmonary sequestration using three-dimensional power Doppler ultrasound. Ultrasound Obstet Gynecol 2005;25:128-133.
  10. Savic B, Birtel FJ, Tholen W. Lung sequestration. Report of seven cases and review of 540 published cases. Thorax 1979;34:96-100.
  11. Becmeur F, Horta-Geraud P, Donato L, Seavage P. Pulmonary sequestrations: prenatal ultrasound diagnosis, treatment, and outcome. J Pediatr Surg 1998;33:492-496.
  12. Salomon LJ, Audibent F, Dommengues M, Vial M, Frydman R. Fetal thoracoamniotic shunting as the only treatment for pulmonary sequestration with hydrops: favorable long-term outcome without postnatal surgery. Ultrasound Obstet Gynecol 2003;21:299-301.
  13. Cass DL, Crombleholme TM, Howell LJ, Stafford PW, Ruchelli ED, Adzick NS. Cystic lung lesions with systemic arterial blood supply: A hybrid of congenital cystic adenomatoid malformation and bronchopulmonary sequestration. J Pediatr Surg 1997;32:986-990.
  14. Zeidan S, Gorincour G, Potier A, Ughetto F, Dubus JC, Chrestian MA, Grosse C, Gamerre M, Guys JM, de Lagauise P. Congenital lung malformation: evaluation of prenatal and postnatal radiological findings. Respirology 2009;14:10005-1011.
  15. Azizkhan RG, Crombleholme TM. Congenital cystic lung disease: contemporary antenatal and postnatal management. Pediatr Surg Int 2008;24:643-657.
  16. Suda H, Matsuda I, Chida S, Maeta H. Neonatal adrenal hemorrhage detected antenatally. Acta Paediatr Jpn 1992;34:606-610.
  17. Bolande RP, Brough AJ, Izant RJ Jr. Congenital mesoblastic nephroma of infancy. A report of eight cases and the relationship to Wilm’s tumor. Pediatrics 1967;40:272-278.
  18. Powis M. Neonatal renal tumors. Early Hum Dev 2010;86:607-612.
  19. Rempen A, Kirschner T, Fraudendienst-Egger , Hocht B. Congenital mesoblastic nephroma. Fetus 1992;2:1-5.
  20. Curtis MR, Mooney DP, Vaccaro TJ, Williams JC, Cendron M, Shorter NA, Sargent SK. Prenatal ultrasound characterization of the suprarenal mass: distinction between neuroblastoma and subdiaphragmatic extralobar pulmonary sequestration. J Ultrasound Med 1997;6:75-83.
  21. Maas KL, Feldstein VA, Goldstein RB, Filly RA. Sonographic detection of bilateral chest masses: report of three cases. J Ultrasound Med 1997;16:647-652.
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  23. Cavoretto P, Molina F, Peggi S, Davenport M, Nicolaides KH. Prenatal diagnosis and outcome of echogenic fetal lung lesions. Ultrasound Obstet Gynecol 2008;32:769-783.
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  29. Smalian JC, Guzman ER, Ranzini AC, Benito CW, Vintzileos AM. Color and duplex Doppler sonographic investigation of in utero spontaneous regression of pulmonary sequestration. J Ultrasound Med 1996;19:789-792.
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  32. Knox EM, Kilby MD, Martin WL, Khan KS. In-utero pulmonary drainage in the management of primary hydrothorax and congenital cystic lung lesions: a systematic review. Ultrasound Obstet Gynecol 2006;28:726-734.
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  36. Wilson RD. In utero therapy for fetal thoracic abnormalities. Prenat Diagn 208;28:619-625.
  37. Osaki T, Kodate M, Takagishi T, Nomi M, Murakami J, Yamamoto H. Unique extralobar sequestration with atypical location and aberrant vessels. Ann Thorax Surg 2010;9:1711-1712.
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