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Obstetrics & Gynecology 1999;94:567-571
© 1999 by The American College of Obstetricians and Gynecologists
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ORIGINAL RESEARCH

Fetal Pulmonary Sequestration: A Favorable Congenital Lung Lesion

JOHN B. LOPOO, MD, RUTH B. GOLDSTEIN, MD, GERALD S. LIPSHUTZ, MD, JAMES D. GOLDBERG, MD, MICHAEL R. HARRISON, MD and CRAIG T. ALBANESE, MD

From the Fetal Treatment Center, and the Departments of Radiology and Obstetrics and Gynecology, University of California San Francisco, San Francisco, California.

Address reprint requests to: Craig T. Albanese, MD The Fetal Treatment Center University of California, San Francisco 513 Parnassus Avenue, Rm 1601-HSW San Francisco, CA 94143-0570 E-mail: craig{at}itsa.ucsf.edu


   Abstract
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Abstract
Materials and Methods
 Results
 Discussion
 References
 
Objective: We reviewed the perinatal clinical course of prenatally diagnosed pulmonary sequestrations to determine the natural history of this anomaly.

Methods: From January 1992 to August 1998, 192 women were referred to the University of California, San Francisco, Fetal Treatment Center because obstetric ultrasound had demonstrated fetal lung lesions. In 14 fetuses, the echogenic lung masses were pulmonary sequestrations deriving arterial blood supply from clearly identifiable systemic arteries rather than the pulmonary artery. We examined records of the 14 fetuses and documented the location of the lesion, gestational age at diagnosis, need for fetal intervention, prenatal and postnatal complications, gestational age at delivery, and survival.

Results: There were 16 intrathoracic pulmonary sequestrations in 14 fetuses (eight left-sided, four right-sided, two bilateral). Three fetuses had histologically mixed lesions (congenital cystic adenomatoid malformation and pulmonary sequestration). The mean age at diagnosis was 23 weeks’ gestation (range 19–31 weeks). Two fetuses required prenatal intervention (placement of a thoracoamniotic shunt for drainage of an ipsilateral tension hydrothorax). The mean gestational age at delivery was 37 weeks (range 32–40 weeks). The large lesions of four fetuses regressed completely prior to birth, and the lesions of the remaining ten fetuses were electively resected after birth without causing morbidity or mortality.

Conclusion: Pulmonary sequestrations are a subgroup of congenital lung lesions with a favorable outlook; many regress prenatally, and the persistent ones are resected safely postnatally. Pulmonary sequestrations cause hydrops only because of a tension hydrothorax, which can be drained prenatally, if necessary.

Pulmonary sequestrations are congenital lesions comprised of nonfunctional lung tissue that does not communicate with the normal tracheobronchial tree. Lesions receive systemic arterial blood supply from an aberrant aortic branch and are drained by pulmonary veins of the azygous or hemiazygous system.1 The combination of an aberrant systemic blood supply (identified by color-flow Doppler sonography) and an echogenic lung mass is pathognomonic for the prenatal diagnosis of pulmonary sequestration.2–4

Pulmonary sequestrations and congenital cystic adenomatoid malformations have been categorized as congenital cystic lung lesions.5 It is known that congenital cystic adenomatoid malformation can regress prenatally, stay the same size, or grow and produce pulmonary hypoplasia, hydrops, or both.5–9 It follows that fetuses with a pulmonary sequestration can have the same natural history and thus theoretically the same adverse prenatal events as those fetuses with congenital cystic adenomatoid malformation. The purpose of this study was to examine the perinatal course of pulmonary sequestrations diagnosed by prenatal ultrasound to better understand the natural history of this anomaly as a potentially distinct congenital lung lesion.


   Materials and Methods
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Abstract
 Materials and Methods
Results
 Discussion
 References
 
A total of 192 women whose fetuses were diagnosed with a congenital lung lesion between January 1992 and August 1998 were evaluated at the Fetal Treatment Center at The University of California, San Francisco. Records were reviewed retrospectively to find paitents diagnosed sonographically with a pulmonary sequestration. The ultrasonographic criteria used for diagnosis of a pulmonary sequestration were the presence of an echogenic fetal thoracic mass and an aberrant systemic arterial supply by color-flow Doppler (Figure 1Go). The sonograms of all patients diagnosed with a pulmonary sequestration were examined for size of the sequestration and degree of mediastinal shift. Sequestrations were small if they occupied less than one-third of the hemithorax, moderate if between one-third and two-thirds of the hemithorax, and large if greater than two-thirds of the hemithorax. Mediastinal shift of the heart was designated mild, moderate, or severe. Mediastinal shift was mild if slight or to the point of entering the contralateral hemithorax, moderate if deviated into the contralateral hemithorax without touching the contralateral thoracic wall, and severe if touching the contralateral thoracic wall. We were unable to locate one sonogram and used data obtained from the original written interpretation, which did not include such specific information on the size and degree of mediastinal shift. Unless the lesion disappeared, all ultrasonographic findings were compared with findings at surgery and pathologic examination of resected material. The following data were collected: location of lesion, gestational age at diagnosis, need for fetal intervention, perinatal clinical course (including the development of hydrops, effusions, and neonatal respiratory distress), gestational age at delivery, and survival. Hydrops was defined as an accumulation of fluid in two or more body spaces, edema of the soft tissues that was not caused by fetomaternal blood group incompatibility or both.10,11



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  		Figure 1. Prenatal ultrasound at 22 weeks’ gestation demonstrating an extralobar sequestration (s), shifted heart (h), everted diaphragm (d), and an aberrant systemic feeding artery (f) originating from the aorta (a).

 

   Results
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Abstract
 Materials and Methods
 Results
Discussion
 References
 
Of the 192 fetal lung lesions identified, there were 16 pulmonary sequestrations (all intrathoracic) in 14 patients (Table 1Go).12 The mean gestational age at diagnosis was 23 weeks (range 19–31). Eight of 14 (57%) fetuses had isolated left-sided pulmonary sequestrations, four (29%) were right-sided, and two were bilateral (14%).


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  		Table 1. Clinical Characteristics of 14 Prenatally Diagnosed Pulmonary Sequestrations
 
Two fetuses required prenatal intervention. One fetus developed a tension hydrothorax at 23 weeks’ gestation that caused marked mediastinal shift and was associated with fetal ascites. A thoracentesis was performed with transient resolution of the effusion and restoration of the mediastinum to the midline. When the effusion reaccumulated (demonstrated on ultrasound 2 days later), a thoracoamniotic shunt (Rocket Co. Inc., Branford, CT) was placed. The shunt successfully drained the effusion throughout the remaining 10 weeks of pregnancy, and the ascites resolved. The second fetus developed a tension hydrothorax with marked mediastinal shift, ascites, and skin and scalp edema. The placement of thoracoamniotic shunt (Rocket Co. Inc.) resolved the ascites and skin and scalp edema. Premature rupture of membranes caused premature delivery at 33 weeks. The infant did well postnatally.

Despite large lesions and mediastinal shift, no fetus developed pulmonary hypoplasia. Ultrasound showed that the lesions of four fetuses had disappeared completely prenatally, and all four children had uneventful perinatal courses. The mean gestational age at delivery was 37 weeks (range 32–40 weeks), and all children with lesions demonstrated by chest radiograph or computed tomography scan at birth (n = 10) underwent uneventful postnatal resection. All children are alive to date with a mean follow up of 39 months (range 4–77 months). The only associated anomaly was Down syndrome in one child.


   Discussion
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Abstract
 Materials and Methods
 Results
 Discussion
References
 
Pulmonary sequestration is a rare congenital lung lesion found in 8% of all fetuses diagnosed with congenital lung lesions in the past 6 years at this institution. This number may be underestimated because fetuses may have been misdiagnosed with other lung lesions such as congenital cystic adenomatoid malformation. Despite their significant size and mediastinal shift effects, lesions caused minimal morbidity and no mortality. There are, however, documented complications of pulmonary sequestration. A review of the English language literature revealed 22 cases of complicated fetal thoracic pulmonary sequestrations (Table 2Go).2,3,12–25 Ten of these cases were diagnosed prenatally as sequestrations. Nearly all reported cases had pleural effusions associated with hydrops, but in five cases with hydrops, however, no mention was made of associated pleural effusions. None of these case reports gave the number of sequestrations without perinatal complications. In our series we use a demoninator of uncomplicated pulmonary sequestrations and all lung lesions are compared.


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  		Table 2. Literature Review of Prenatally Diagnosed Pulmonary Sequestrations Associated With Pleural Effusion or Hydrops
 
The cause of ipsilateral effusions associated with pulmonary sequestration remains uncertain. It has been postulated that the vascular pedicle leading to the sequestration can become twisted resulting in venous and lymphatic obstruction.3 Alternatively, the effusion may develop from a large pressure gradient between a systemic artery and the pulmonary vein.22 Regardless of etiology, large persistent effusions cause not only lung compression leading to pulmonary hypoplasia but also result in possible vena caval compromise due to mediastinal shift. This cascade of pathophysiology leads to hydrops and the associated risk of premature delivery and perinatal death. Draining these effusions in utero, thereby decompressing the fetal thorax, can improve survival,16,25–28 however, the means to effect adequate drainage remains controversial. Some authors advocate serial thoracentesis,23 whereas others recommend thoracoamniotic shunting.16,24,27,29 There are also reports of successful expectant management in hydropic fetuses with pulmonary sequestration.17,19 Thoracentesis alone often results in rapid reaccumulation of fluid, presumably because the underlying pathophysiology leading to the effusion has not been corrected. It may be more logical, therefore, to place a thoracoamniotic shunt to decompress the fetal thorax. This procedure does not address the underlying pathophysiology, but it allows for continuous decompression. Figure 2Go is an algorithm for the evaluation of a fetal lung lesion and suggested management of a pulmonary sequestration.



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  		Figure 2. Algorithm for the evaluation and treatment of a prenatally diagnosed pulmonary sequestration. CCAM = congenital cystic adenomatoid malformation; US = ultrasound.

 
In a large series of postnatally diagnosed pulmonary sequestration, an associated anomaly rate of 58%1 was reported, in striking contrast to the single child with an associated anomaly (Down syndrome) in this series. This may, in part, be explained by the aforementioned series that identified lesions postnatally and did not consider patients who might have had disappearing lesions.5,6,8,9 This subpopulation of patients was 29% (four patients) of the present series. The low number of anomalies seen in the present study might also result from referral bias to our institution given its tertiary referral nature.

Technology can reliably differentiate pulmonary sequestrations from other lung lesions. This distinction allows accurate prenatal counseling, surveillance, and formulation of a treatment plan based on the known, relatively favorable natural history of pulmonary sequestration.


   Footnotes
 
PII S0029-7844(99)00420-2

Received January 20, 1999. Received in revised form April 2, 1999. Accepted April 8, 1999.


   References
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Abstract
 Materials and Methods
 Results
 Discussion
 References
 
1. Savic B, Birtel FJ, Tholen W, Funke HD, Knoche R. Lung sequestration: Report of seven cases and review of 540 published cases. Thorax 1979;34:96–101.[Medline]

2. Romero R, Chervenak FA, Kotzen J, Berkowitz RL, Hobbins JC. Antenatal sonographic findings of extralobar pulmonary sequestration. J Ultrasound Med 1982;1:131–2.[Medline]

3. Hernanz-Schulman M, Stein S, Neblett WW, Atkinson JB, Kirchner SG, Heller RM, et al. Pulmonary sequestration: Diagnosis with color Doppler sonography and a new theory of associated hydrothorax. Radiology 1991;180:817–21.[Abstract/Free Full Text]

4. Sauerbrei E. Lung sequestration duplex Doppler diagnosis at 19 weeks gestation. J Ultrasound Med 1991;10:101–5.[Medline]

5. Adzick NS. Fetal thoracic lesions. Semin Pediatr Surg 1993;2:103–8.[Medline]

6. MacGillivray TE, Harrison MR, Goldstein RB, Adzick NS. Disappearing fetal lung lesions. J Pediatr Surg 1993;28:1321–5.[Medline]

7. Adzick NS, Harrison MR, Flake AW, Howell LJ, Golbus MS, Filly RA. Fetal surgery for cystic adenomatoid malformation of the lung. J Pediatr Surg 1993;28:806–12.[Medline]

8. Smulian J, Guzman E, Ranzini A, Benito C, Vintzileos A. Color and duplex Doppler sonographic investigation of in utero spontaneous regression of pulmonary sequestration. J Ultrasound Med 1996;15: 789–92.[Abstract]

9. Bromley B, Parad R, Estroff JA, Benacerraf BR. Fetal lung masses: Prenatal course and outcome. J Ultrasound Med 1995;14:927–36.[Abstract]

10. Norton M. Nonimmune hydrops fetalis. Semin Perinatol 1994;18: 321–2.[Medline]

11. Holzgreve W, Holzgreve B, Curry C. Nonimmune hydrops fetalis: Diagnosis and management. Semin Perinatol 1985;88:52–67.

12. 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: 986–90.[Medline]

13. Becmeur F, Horta-Geraud P, Donato L, Sauvage P. Pulmonary sequestrations: Prenatal ultrasound diagnosis, treatment, and outcome. J Pediatr Surg 1998;33:492–6.[Medline]

14. Boiskin I, Bruner JP, Jeanty P. Lung, extralobar intrathoracic sequestration, torsion. The Fetus 1991;1:74 85.

15. Burs F, Nikkels PG, van Loon AJ, Okken A. Nonimmune hydrops fetalis and bilateral pulmonary hypoplasia in a newborn infant with extralobar pulmonary sequestration. Acta Paediatr 1993;82: 416–8.[Medline]

16. Chan V, Greenough A, Nicolaides KN. Antenatal and postnatal treatment of pleural effusion and extra-lobar pulmonary sequestration. J Perinat Med 1996;24:335–8.[Medline]

17. da Silva OP, Ramaratnam R, Romano W, Bocking A, Evans M. Nonimmune hydrops fetalis, pulmonary sequestration, and favorable neonatal outcome. Obstet Gynecol 1996;88:681–3.[Abstract]

18. Davies PF, Shevland JE, Townley G. Antenatal diagnosis of extra-lobar sequestration. Australas Radiol 1989;33:290–2.[Medline]

19. Evans MG. Hydrops fetalis and pulmonary sequestration. J Pediatr Surg 1996;31:761–4.[Medline]

20. Jouppila P, Kirkinen P, Herva R, Koivisto M. Prenatal diagnosis of pleural effusions by ultrasound. J Clin Ultrasound 1983;11:516–9.[Medline]

21. Kristoffersen SE, Ipsen L. Ultrasonic real time diagnosis of hydrothorax before delivery in an infant with extralobar lung sequestration. Acta Obstet Gynecol Scand 1984;63:723–5.[Medline]

22. Thomas CS, Leopold GR, Hilton S, Key T, Coen R, Lynch F. Fetal hydrops associated with extralobar pulmonary sequestration. J Ultrasound Med 1986;5:668–71.[Medline]

23. Weist E, Raudies G. Successful prenatal therapy of pleural effusion secondary to lung sequestration by serial thoracocentesis. Fetal Diagn Ther (in press).

24. Weiner C, Varner M, Pringle K, Hein H, Williamson R, Smith WL. Antenatal diagnosis and palliative treatment of nonimmune hydrops fetalis secondary to pulmonary extralobar sequestration. Obstet Gynecol 1986;68:275–80.[Medline]

25. Dolkart LA, Reimers FT, Helmuth WV, Porte MA, Eisinger G. Antenatal diagnosis of pulmonary sequestration: A review. Obstet Gynecol Surv 1992;47:515–20.[Medline]

26. Castillo RA, Devoe LD, Falls G, Holzman GB, Hadi HA, Fadel HE. Pleural effusions and pulmonary hypoplasia. Am J Obstet Gynecol 1987;157:1252–5.[Medline]

27. Longaker M, Laberge JM, Dansereau J, Langer JC, Crombleholme TM, Callen PW, et al. Primary fetal hydrothorax: Natural history and management. J Pediatr Surg 1989;24:573–6.[Medline]

28. Rodeck CH, Fisk NM, Fraser DI, Nicolini U. Long-term in utero drainage of fetal hydrothorax. N Engl J Med 1988;319:1135–8.[Medline]

29. Morrow RJ, Macphail S, Johnson JA, Ryan G, Farine D, Knox Ritchie JW. Midtrimester thoracoamniotic shunting for the treatment of fetal hydrops. Fetal Diagn Ther 1995;10:92–4.[Medline]





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