Fetal and Pediatric Pathology, Early Online:1–5, 2012Copyright C© Informa Healthcare USA, Inc.ISSN: 1551-3815 print / 1551-3823 onlineDOI: 10.3109/15513815.2012.671443

Magnetic Resonance vs. Sonographic Imaging:Diagnostics of a Large Congenital PulmonaryAirway Malformation

Zoltan Kozinszky, MD, PhD,1 Attila Kereszturi, MD, PhD,1 NorbertPasztor, MD,1 Jozsef Daru, MD, PhD,1 Janos Sikovanyecz, MD, PhD,1

Laszlo Kaiser, MD,2 Peter Milassin, MD,3 and Attila Pal, MD, PhD1

1Department of Obstetrics and Gynecology, University of Szeged, Szeged, Hungary;2Department of Pathology, University of Szeged, Szeged, Hungary; 3Internal Medical Care,University of Szeged, Szeged, Hungary

Sonographic scan revealed a homogenously hyperechogenic lesion in the right fetal lung withmicrocystic pattern by a primigravid women at 22nd weeks of gestation. A large congenital pul-monary airway malformation (CPAM) was suspected with a lesion-to-lung ratio over 90%. The mi-crocystic image of this thoracic anomaly was moderately visible on magnetic resonance imaging(MRI) at that early stage of the pregnancy. Fetopsy confirmed the diagnosis as a pure microcysticCPAM following termination of pregnancy. A controlled prospective study could be performed tocompare ultrasound as a diagnostic modality to the MRI, focusing on volumetry, signal character-istics, and follow-up/regression of fetal pulmonary malformations.

Keywords magnetic resonance imaging (MRI), ultrasound, congenital pulmonary airwaymalformation (CPAM)

INTRODUCTION

A 21-year-old woman, gravida 1 para 0, was referred to our unit at 21 weeks gestationfor a routine detailed anatomy scan. The pregnancy had been uncomplicated and ul-trasound (US) (Kretz Sonoace 8000, Voluson 730 Pro, Zipf, Austria) examination at 12weeks gestation had revealed no anomaly. Fetal growth and the amniotic fluid volumewere appropriate; there was no sign of hydrops or other fetal abnormalities except for ahyperechogenic focus in the right cardiac ventricle, and a hyperechogenic mass in theright lung but the exact intrapulmonary localization was impossible. No feeding arterywas detected with a color doppler US. These findings were confirmed at a repeatedUS examination at 22 weeks. The lesion that involved the entire right hemithorax washomogenously hyperechogenic, suggesting a microcystic pattern (solid with multiplecysts <5 mm in diameter) as type 3 [1], and it was approximately five times larger(4.5 × 3.6 × 4.1 cm) than the normal echogenic left lung [2]. The tentative diagnosiswas a congenital pulmonary airway malformation (CPAM) with a lesion-to-lung ratioover 90%. The cystic adenomatoid volume (CVR) ratio (volume of the CPAM dividedby the head circumference) [3] was 2.9, and a severe mediastinal shift (the heartabutting the chest wall) was also evident, whereas hydrops was not present.

Address correspondence to Dr. Zoltan Kozinszky, Department of Obstetrics and Gynecology,University of Szeged, Szeged, Hungary. E-mail: kozinszkyz@yahoo.com

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FIGURE 1 T2-weighted image of the fetal lungs.

A magnetic resonance imaging (MRI) was performed using a 1.5T MR scanner(Gyrex V Dlx Elscint, Elscint Ltd.; Haifa, Israel), a torso phased-array coil, and imagesequence was T2-weighted coronal and axial scans: the fetal heart is dislocated to theleft side, and the left lung is small (Figure 1). To avoid misregistration caused by fetalmovement, each new acquisition was performed according to the images obtained inthe immediately preceding acquisition. Magnetic resonance imaging parameters were∞/98 (repetition time msec/effective echo time msec), a 31.2-kHz bandwidth, and atotal imaging time of 18–25 sec to acquire 15 contiguous sections. This acquisition timeallowed maternal breathholding.

After acquisition of the series of images depicting the abnormalities, transverse im-ages were obtained through the chest of the fetus. The section thickness and intersec-tion gap were 4 and 0 mm, respectively. The CPAM mass were excluded from MR lungvolumetry resulting in a 16-ml fetal lung volume. Detailed volumetric measurementsdemonstrated that the mass volume relative to the thoracic cavity volume was 71%. Thefeeding artery could be visualized and the microcystic image of this thoracic anomaly

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Imaging of CCAML

was moderately visible on MRI. Magnetic resonance images were reviewed by an ex-perienced radiologist (P.M.). The right hemi-thorax was wide and filled up with a nor-mally structured lung, which had the same signal intensity as the left one. The mass inthe right lung displaced and compressed the heart and the left lung with an adjacentpartial diaphragmatic eversion.

Four days later, the follow-up US scan performed by the same sonographer (A.K.)confirmed the MRI diagnosis. The right-left lung ratio was higher than earlier (approx-imately 8:1) and the CVR dramatically increased to 4.2 [3]. The mass volume relativeto the thoracic cavity volume was 78%. The cystic mass grew in size in absolute termsalso to 5.2 × 4.3 × 4.4 cm [4]. No hydrops or other malformation was detected. The pa-tient requested termination of pregnancy despite the detailed information provided incounseling, emphasizing the low overall perinatal mortality rate (12%), the high rateof size reduction (47%) [5], resulting in an excellent prognosis even in cases of largeCPAM or when these are associated with mediastinal shift [5, 6]. Fetopsy confirmedthe US diagnosis as a pure microcystic CPAM (not mixed with bronchopulmonary se-questration [BPS]). The left lung was 3.6 g and 30 × 20 × 15 mm in size. The right lungwas 21 g, enlarged, 50 × 45 × 40 mm in size, did not contain bronchioles, and it ap-peared solid on gross examination. The right main bronchus strictured 9 mm from itsorigin, and did not react to a breathing test. Ninety percent of the right lung containedvarious cuboidal, columnar, and depressed epithelial areas with partial broncholysis,sequestered by numerous alveolus-sized cystic structures (ductules and saccules alsolined by epithelial cells). A moderate, interstitial edema and a mainly subpleural lym-phangiectasy was revealed. The bronchial structures, i.e., cartilage and tubular glands,were absent. The lumen of the trachea was replaced by fibrocollagenous stroma withsome cysts. There was no other malformation recorded.

Congenital pulmonary airway malformation is characterized by an adenomatoidproliferation of bronchiole-like structures and cyst formation. The abnormality usu-ally develops between the fourth and the seventh weeks of fetal life [7]. Based onthe size of the cysts, CPAMs may be classified into five different types [1]. Type 3 le-sions are composed of multiple microscopic, adenomatoid cysts (each less than 0.5mm in diameter) lined by ciliated cuboidal ,and columnar epithelium without ob-vious cyst formation. An entire lobe is usually involved and arises from the termi-nal bronchiolar/alveolar duct region during the development of the tracheobronchialtree. Neither can mucous cells, cartilage, striated muscle fibers, and pulmonary ves-sels be seen in them. Type 3 lesions do not collapse during pregnancy; therefore, theinfants may develop severe respiratory distress shortly after birth with this abnormality[1, 7].

Congenital pulmonary airway malformation in our case showed an unusually ex-cessive growth in its volume and peaked at 75%, relative to the total thoracic volume,which is extremely high as compared to that which had been published previously byKunisaki et al. [6]. Typically, type 3 CPAM appears as a large, solid, homogenous mass[1, 6, 8]. According to Crombleholme et al. [3], a CVR higher than 1.6 predicts hydropsat a later gestation, which is followed by a poor prognosis. Generally, the larger thelesion is at initial examination, the less likely it is to regress completely [6, 8], and forfetuses with a CVR greater than 1.6, the perinatal survival is 63% [6] with poor regres-sion [6, 8].

The exponentially growing malformation presented in our report compressed thenormal developing lung which would have led to pulmonary hypoplasia. The masswould have compressed the inferior vena cava and heart, leading to severe hydropsand cardiac output failure later on and would have obstructed the esophagus. In thiscase, the probability of survival would have been low in the absence of surgical inter-vention [4, 6].

Copyright C© Informa Healthcare USA, Inc.

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The problems associated with sonographic measurements in quantifying volumechanges are well known. Because of fetal development, there is an inherent vari-ability in obtaining serial measurements from the same plane. In addition, volumemeasurements by ultrasound can be inaccurate owing to a similarity between theechogenicity of the mass and the normal parenchyma as gestation progresses [9].However, our case as a Stocker type 3 lesion exhibited such a rapid progress that theMRI/ultrasonographic volumetry were correct and the outline of the mass could bevisualized.

Consistently with previous reports [8], we might conclude that an MRI is useful asa diagnostic tool; however, ultrasound could also be used for volumetry of the fetallungs and intrauterine pulmonary pathologic conditions, as in this case in the diag-nosis of microcystic parenchymal lung lesions. Both imaging modalities seem to bevaluable in follow-up volumetry (in detecting regression) and in the determination ofthe dislocation of the mediastinum.

In this case report, we presented a fetus in the 21 week gestation with a very largeCPAM, which was revealed in the course of a routine US screening. Ultrasound clearlyevaluated the mass as this lesion had typical US characteristics (microcystic, hyper-intense, homogenous, mass) in our case as Roelofsen et al. [4] previously described.An MRI helped us gain insight into the impact of mass size in relationship to adjacentthoracic structures and confirmed the diagnosis. A controlled prospective study couldbe performed to compare ultrasound as a diagnostic modality to the MRI, focusing onvolumetry, signal characteristics, and follow-up/regression.

Upon further management, prenatal counseling is needed, although it is very dif-ficult to distinguish between the microcystic CPAM and other lesions (such as mixedBPS with CPAM [8], congenital lobar fluid overload [6, 8, 10], or other hyperechogenicintrathoracic appearances or congenital laryngotracheal obstruction)that has poorprognosis [4]. Both BPS and microcystic malformation have a homogenous hyperin-tensive appearance without visible cysts [8], although BPS has a feeding artery [6, 8,10]. A high lesion-to-lung ratio is also not distinctive between CPAM and BPS [8], al-though it is characteristic for macrocystic and not for microcystic type.

Furthermore, the vast majority of the recent literature on MRI of CPAMs (involvingmicrocystic cases among type I and type II cases or other mixed cases) is designed witha retrospective review of the images by radiologists [6, 8, 10]. Moreover, none of theprevious studies have reported on the definitive characteristics of microcystic struc-ture by MRI. Although a microcystic structural appearance tends to grow with lessintensity compared to the macrocystic form [6], further study should be designed toelucidate from which mass size or at what gestational age it is distinctively detectablefor MRI. Unfortunately, the patient chose the termination of the pregnancy despite thecounseling focusing on the previously reported fact that large CPAMs show significantregression by the start of the third trimester and consequently we could not follow upwith the presented case.

Declaration of InterestThe authors report no conflict of interest. The author alone is responsible for the con-tent and writing of this article.

REFERENCES

[1] Stocker JT. Congenital pulmonary airway malformation - a new name for and an expanded classifica-tion of congenital cystic adenomatoid malformation of the lung. Histopathology 41(suppl 2):424–31,2002.

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[2] Cavoretto P, Molina F, Poggi S, Davenport M, Nicolaides KH. Prenatal diagnosis and outcome ofechogenic fetal lung lesions. Ultrasound Obstet Gynecol 32:729–31, 2008.

[3] Crombleholme TM, Coleman B, Hedrick H, Liechty K, Howell L, Flake AW, Johnson M, Adzick NS.Cystic adenomatoid malformation volume ratio predicts outcome in prenatally diagnosed cystic ade-nomatoid malformation of the lung. J Pediatr Surg 37:331–8, 2002.

[4] Roelofsen J, Oostendorp R, Volovics A, Hoogland H. Prenatal diagnosis and fetal outcome of cys-tic adenomatoid malformation of the lung: case report and historical. Ultrasound Obstet Gynecol4:78–82, 1994.

[5] Ierullo AM, Ganapathy R, Crowley S, Craxford L, Bhide A, Thilaganathan B. Neonatal outcome ofantenatally diagnosed congenital cystic adenomatoid malformations. Ultrasound Obstet Gynecol26:150–3, 2005.

[6] Kunisaki SM, Barnewolt CE, Estroff JA, Ward VL, Nemes LP, Fauza DO, Jennings RW. Large fetalcongenital cystic adenomatoid malformations: growth trends and patient survival. J Pediatr Surg42:404–10, 2007.

[7] Gornall AS, Budd JLS, Draper ES, Konje JC, Kurinczuk JJ. Congenital cystic adenomatoid malforma-tion: accuracy of prenatal diagnosis, prevalence and outcome in a general population. Prenat Diag23:997–1002, 2003.

[8] Liu YP, Chen CP, Shih SL, Chen YF, Yang FS, Chen SC. Fetal cystic lung lesions: evaluation with mag-netic resonance imaging. Pediatr Pulmonol 45:592–600, 2010.

[9] Saltzman DH, Adzick NS, Benacerraf BR. Fetal cystic adenomatoid malformation of the lung: appar-ent improvement in utero. Obstet Gynecol 71:1000–2, 1988.

[10] Levine D, Barnewolt CE, Mehta TS, Trop I, Estroff J, Wong G. Fetal thoracic abnormalities: MR imag-ing. Radiology 228:379–88, 2003.

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