Magnetic resonance imaging for congenital lung malformations

Abstract

Congenital lung malformations are most often identified on prenatal US screening. Fetal MRI is often performed to further evaluate these lesions. Although some of these lesions might cause prenatal or early postnatal symptoms that require urgent management, the majority are asymptomatic at birth and might be subtle or invisible on chest radiographs. Postnatal imaging is frequently deferred until 3-6 months of age, when surgery or long-term conservative management is contemplated. High-quality imaging and interpretation is needed to assist with appropriate decision-making. Contrast-enhanced chest CT, typically with angiographic technique, has been the usual postnatal imaging choice. In this review, the author discusses and illustrates the indications and use of postnatal MR imaging for bronchopulmonary malformations as well as some differential diagnoses and the advantages and disadvantages of MR versus CT.

Keywords: Bronchopulmonary malformation; Infants; Lung; Magnetic resonance imaging; Postnatal.

Fig. 1

Cystic pleuropulmonary blastoma (PPB) in a 19-month-old boy with no abnormal prenatal history. He had MRI for an abdominal mass, with an incidental finding of lower right lung cyst. a Coronal T2-weighted MRI shows a large multiloculated cystic mass in the right kidney, likely a multilocular cystic nephroma. There is an incidental finding of a prominent air-filled cyst in the medial right lower lobe (arrow). Note the anesthesia-related atelectasis at the lung bases, left greater than right. These findings raised concerns that the chest lesion might be cystic pleuropulmonary blastoma, which can be associated with other tumors including multilocular cystic nephroma. In many cases there is an associated DICER1 genetic mutation (found later to be present in this child). b Subsequent chest CT scan, coronal reconstruction, shows a large medial right-lower-lobe cyst (solid arrow), as seen on earlier MRI. There are also several smaller scattered intrapulmonary cysts, one of which is shown on the left (dashed arrow). The most likely diagnosis was PPB. The lack of prenatal history of a cystic lung lesion, peripheral location, multiple cystic foci and association with DICER1 mutation and another neoplasm all served to differentiate this case from congenital pulmonary airway malformation. The large right lower lobe cyst was resected and confirmed pathologically as type 1 cystic PPB. The other cysts were to be followed clinically and by imaging. These could grow and evolve into a more aggressive type of PPB; however, they could also become quiescent cysts

Fig. 2

Imaging in a 13-day-old boy with known left-lower-lobe lesion prenatally and incidental imaging of pulmonary sequestration on a spine MRI. a Anteroposterior chest radiograph shows an ill-defined medial left-lower-lobe density. T9 vertebral anomaly (arrow) led to spine MR for evaluation of possible associated cord abnormality. b Axial T2-weighted MR image of lung bases from spine MR shows anterior saturation band to enhance spine imaging. There is a nonaerated, moderately vascular and somewhat T2-bright lesion in the posteromedial left lower lobe, with systemic arterial supply (dark-blood sequence) from the lower thoracic aorta (solid arrow) and venous drainage toward a systemic vein (dashed arrow), consistent with an extralobar pulmonary sequestration. SPLN spleen. c Coronal T2-weighted image from spine MR demonstrates the triangular medial left-lower-lobe nonaerated sequestration. In addition to central dark branching vessels, there is a bright central branching structure (arrow) within the sequestration from mucoid impaction in bronchi, consistent with associated bronchial atresia. Note the absence of the left kidney, with bowel in the left renal fossa

Fig. 3

Incidental chest mass in a 12-year-old boy presenting with back and abdominal pain. a Contrast-enhanced CT scan for appendicitis (negative abdomen), axial slice at the lung bases, shows a poorly enhancing mass (arrow) in the right lower lobe versus posterior mediastinum. There is a small right pleural effusion. b Sagittal T2-W MR obtained to further evaluate the right-side mass shows an oval T2-hypointense mass in the right lower lung posteriorly (arrow), surrounded by T2-hyperintense pleural fluid. c Axial T1-weighted post-contrast MRI of the right lung base shows that the posteromedial oval right-lower-lobe mass (arrow) has minimal peripheral enhancement. Note that the pleural fluid is T1-hyperintense, suggesting blood (containing methemoglobin and protein-rich plasma) or other protein-rich fluid with T1-shortening effects. The boy’s pain symptoms, location and appearance of the lesion with absent perfusion as well as T1/T2 bright pleural fluid suggested the diagnosis of a torsed, infarcted extralobar pulmonary sequestration with hemorrhagic pleural effusion. This was subsequently confirmed surgically and on pathology

Fig. 4

Right-lower-lobe lesion identified in utero and then lost to follow-up postnatally until 2 years of age in a girl. a Axial T2-weighted prenatal MRI slice at 22 weeks of gestation. Segmental homogeneous T2-hyperintense right-lower-lobe mass (arrow) was thought to most likely represent segmental lung overinflation. The lesion was much smaller and less T2-bright on a follow-up fetal MR at 37 weeks of gestation (not shown). b The girl had MRI at 2 years old (parents preferred to avoid CT radiation exposure). Axial T2-weighted image shows a posteromedial right-lower-lobe lesion (long arrow) with central hyperintense mucoid impaction (short arrow) and surrounding air-trapping, consistent with segmental bronchial atresia with overinflation. Note how much brighter the mucoid impaction is than adjacent vessels. c Coronal T2-W MR image shows T2-bright branching mucoid impaction in the lesion (arrow). This MR was obtained before the availability of ultra-short echo-time imaging of the lung, so the lung detail is relatively poor. d Follow-up coronal contrast-enhanced CT at 3 years of age shows a posteromedial segmental hyperlucency (arrow) with central mucoid impaction (arrowhead), again confirming segmental overinflation with bronchial atresia. The mucoid-impacted bronchus is a little larger but only slightly less dense than vessels and can be difficult to identify on CT. This lesion was not resected

Fig. 5

Follow-up prenatal MR in a fetus with a history of twin–twin transfusion syndrome with laser ablation and fluid amnioreduction, with demise of the smaller donor twin at 22 weeks. a Fetal MRI at 31 weeks of gestation shows multiple T2-hyperintense large cysts in both lungs (arrows), which were not present on the prior MR. b CT scan of the girl at 4 months of age. Coronal reconstruction shows multiple air-filled lung cysts (arrows). c MRI age 10 months (parents did not want repeat CT). Axial ultra-short echo-time T1-weighted post-contrast sequence shows a multilocular air-filled cystic lesion (arrow) at the left lung base, similar to findings on prior CT. There is moderate posterior-dependent anesthesia-related atelectasis. d MRI at age 2 years. Coronal T1-W ultra-short echo-time post-contrast sequence shows the air-filled cysts unchanged (arrows). The etiology of these lesions was not entirely clear; they were not resected or biopsied. However, cystic lung lesions have been described in other twin–twin pregnancies that were thought to be most consistent with congenital pulmonary airway malformations on pre- and postnatal imaging [25]

Fig. 6

Follow-up imaging in a 4-month-old girl with a prenatal diagnosis of left-lower-lobe congenital pulmonary airway malformation (CPAM). There was a subtle lower-lobe opacity on chest radiograph at birth (not shown). MRI was obtained at 4 months to confirm whether the lesion was still present. Parents refused CT because of ionizing radiation exposure. a Axial T2-weighted (black-blood) MR sequence shows a multi-cystic air-filled lesion (arrows) in the posterior left lower lobe, consistent with large-cyst CPAM (largest cyst >2 cm). The surrounding normal left lung is atelectatic; there is also right-side-dependent atelectasis. b Coronal T1-weighted post-contrast MR image shows left-lower-lobe aerated large cyst CPAM (arrow). No abnormal systemic arterial supply is seen. The entire remaining left lung is atelectatic from inadvertent right bronchus intubation under anesthesia. The persistent aeration of the CPAM lesion reflects air-trapping from an abnormal airway connection; the phenomenon is similar to the prolonged retention of fluid seen in many bronchopulmonary malformations in the neonatal period. If the lesion were not aerated, the atelectatic lung would likely obscure it. The MR images were considered sufficient for surgical guidance for thoracoscopic resection of the left lower lobe. Diagnosis of large-cyst CPAM was confirmed on pathology

Fig. 7

Evaluation of suspected mediastinal mass in an 11-month-old boy with an incidental mass on chest radiograph obtained for cough. a Anteroposterior chest radiograph shows a right superior rounded mediastinal density (arrow), suspected as possible neuroblastoma. b Axial T2-weighted MRI for further evaluation shows a rounded T2-hyperintense middle mediastinal lesion suggestive of a fluid-filled partially septated cyst (arrow). c Coronal T1-weighted post-contrast MRI confirms the cystic nature of the lesion with rim enhancement and close proximity to the airway, consistent with a mediastinal bronchogenic cyst (arrow). These findings were confirmed at surgery and pathology. Images were published in [23] in Fig. 2, reprinted with permission

Fig. 8

Imaging following concern for neuroblastoma versus abdominal sequestration in a newborn girl with prenatal left upper abdominal mass. a Oblique US image with power Doppler shows a mostly solid echogenic mass (solid arrows) in the left upper quadrant adjacent to the spleen (SPLN). There are several small internal cystic components; one is illustrated (arrowhead). Two systemic supplying vessels (dashed arrows) are identified arising from the celiac artery. b Coronal T2-weighted MRI obtained as a wrap-and-feed non-sedated study without contrast agent. Image shows a large heterogeneous T2-hyperintense mass containing tiny cysts in the left upper quadrant (white arrow). The MRI clearly shows that the lesion is separate from and displacing the left adrenal gland inferiorly (black arrow). The MR appearance in combination with US findings strongly suggested an intrabdominal hybrid sequestration lesion, and these are almost always on the left side. Because of persistence and parental concern, the mass was resected at age 4 months and was confirmed to be a bronchopulmonary malformation hybrid with features of sequestration and small-cyst congenital pulmonary airway malformation

Fig. 9

Magnetic resonance imaging in a 5-month-old boy with previous repair of tracheoesophageal fistula, feeding and respiratory problems, and persistent left-lower-lobe opacity on chest radiographs. MRI was obtained to evaluate for vascular ring (no ring found). a Sagittal T1-weighted dark-blood MR image in the left retrocardiac region shows a rounded complex mass in the medial left lower lobe with cystic fluid (solid arrow) and inferior more solid components. In addition, there are smaller round and very dark areas (also T2-dark, not shown) suggestive of air-filled cysts (arrowhead). An aberrant systemic artery approached the mass from the abdomen (dashed arrow). These findings suggested a hybrid sequestration lesion. The presence of air within the mostly nonaerated lesion suggested the possibility of an aberrant connection to the gastrointestinal tract. b Contrast esophagram, anteroposterior view, demonstrates contrast filling of branching dilated airways (arrow) within the left-lower-lobe lesion, confirming an esophageal bronchus connecting to the hybrid bronchopulmonary malformation. Images were published in [1] in Fig. 5. Reprinted with permission from Springer Nature

Fig. 10

Imaging in a 10-day-old boy with respiratory distress and small right lung, with a poor-quality outside CT suggesting complex scimitar syndrome. a Coronal T1-weighted spin-echo MRI shows a cardiomediastinal shift to the right with a small right lung. Left superior vena cava drains to the coronary sinus (arrow). b T1-weighted dark-blood coronal MR slice, more posterior than (a), confirms a right scimitar vein (solid arrow) draining anomalously to the inferior vena cava. Multiple additional anomalies were present, including: extralobar pulmonary sequestration in a nonaerated horseshoe lung component overlying the spine (open arrow); systemic arterial supply to the sequestration from the abdomen with multiple large tortuous vessels in the lesion; partial pulmonary sling with a normal left upper pulmonary artery (arrowhead) and a left lower pulmonary artery arising from the right pulmonary artery (dotted arrow); additionally, there is long-segment tracheal stenosis with a low T-shape carina, a typical configuration associated with pulmonary artery sling. Figure 10b was published in [1] in Fig. 11. Reprinted with permission from Springer Nature

Fig. 11

Imaging in a 2-month-old boy presenting with a cough and fever; he had no chest abnormality seen prenatally. There was a rounded perihilar mass on chest radiograph (not shown), and suboptimal CT suggested differential diagnoses of necrotizing pneumonia or infected congenital pulmonary airway malformation (CPAM) versus neoplasm. a Axial short tau inversion recovery MR image shows a large right lung mass with heterogeneous T2-hyper- and hypointense solid as well as T2-hyperintense fluid-filled cystic components involving the posterior right lung and extending to the mediastinum (arrow) adjacent to the aorta. b Coronal T1-W post-contrast MR shows a right-side perihilar, subcarinal and lower lobe mass with heterogeneously enhancing solid and non-enhancing cystic components extending around the hilum and right bronchi. Infected CPAM was considered unlikely because there was no prenatal history and the nonaerated lesion extended around the bronchi and to the mediastinum. Pleuropulmonary blastoma (PPB) was considered the more likely diagnosis; this would be type 2 (solid/cystic), although almost all PPBs in infancy are type 1 (cystic). Right pneumonectomy was required for complete surgical resection. Initial pathological diagnosis was PPB type 2; subsequent external pathology consultation led to a change in diagnosis to peribronchial myofibroblastic tumor, a rare benign mesenchymal neoplasm found in late prenatal or perinatal ages. This is often a large central tumor that surrounds and entraps airways, and malformed cartilage plates are a prominent histological feature [21]

Fig. 12

Reporting template for bronchopulmonary malformations (BPM)