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•Fig. 18. Sonographic air bronchograms. Transverse

•sonogram shows pleural effusion and lower lobe

•consolidation with internal branching bright echogenicities

•representing air bronchograms. These may•move with patient respiratory effort

•first described in pediatric patients. Entrapped fluid or mucoid material within bronchi in necrotizing or

postobstructive pneumonias produces hypoechoic branching structures, the sonographic fluid bronchogram.

•Pulmonary vascular flow is preserved in simple pneumonic consolidation and is readily demonstrated with color

Doppler.• \With atelectasis, air bronchograms are also present, and

blood vessels become crowded together and have a more parallel orientation

• .Their orderly linear and branching structure is preserved, however, allowing distinction from the more irregular

vasculature found in neoplasms.

•Distinguishing pneumonic consolidation from simple atelectasis can be difficult

radiographically. It has been suggested thatUS can be more specificin this situation

• .If there is movement of the air within bronchi, this usually indicates pneumonia, whereas the air

bronchograms in atelectasis are most often static.

• In a recent study, this dynamic air bronchogram had a sensitivity of 61% and a positive predictive

value of 97% in distinguishing pneumonia from atelectasis.

•Additionally, in adults atelectasis has been reported to transmit cardiac pulsation more

readily than pneumonic consolidation, producing the so-called lung pulse sign .

•I have not found this sign useful in m personal experience, perhaps because of the smaller

thoraces of children and closer proximity of the heart producing pulmonary motion regardless of

the cause of the underlying lung disease.

•As lung infections progress, areas of parenchymal

•necrosis may develop. Small areas of•lung necrosis appear as areas of decreased

echogenicity•(Fig. 19

•Fig. 19. Necrotizing pneumonia. Longitudinal sonogram

•shows consolidation of the left lower lobe•with air bronchograms (arrowhead). There are

several•areas of decreased echogenicity within the lung•(arrows )that showed no flow with color Doppler

indicating•foci of necrosis.

•that lacks color Doppler flow within a region of pulmonary consolidation.

•If the area of necrosis progresses and enlarges faster than can be cleared by the body, a lung

abscess develops.• Larger abscesses may develop a thick wall,

and air fluid levels may be seen if there is cavitation or if the abscess communicates

with the bronchial tree (Fig. 20).

•Fig. 20. Lung abscess. (A) Chest radiograph in a 4-month-old child with a history of

bronchopulmonary dysplasia•shows a thick walled cystic mass in the right

chest (arrowheads) with internal air (arrow). (B) Transverse sonogram

•shows the thick-walled abscess (arrowheads) with internal air (arrow). Percutaneous drainage

and antibiotic•treatment lead to a complete resolution.

•Causative organisms are not always cultured from sputum or peripheral blood.

• If abutting the pleura, lung abscess are sonographically visible, and Usguided

aspiration and drainage can play an important role in diagnosis and treatment.

Masses•Primary lung neoplasms are fortunately rare in children.

Pulmonary blastoma is the most common and usually starts as a peripheral lesion, often attaining large size before

becoming clinically•apparent.• Other less common tumors include mucoepidermoid

carcinoma, rhabdomyosarcoma, and bronchogenic tumors• .Although US can confirm the presence of a mass, like

other imaging modalities US cannot be histologically specific and differentiate among tumor types. As with

pleural lesions, if a lung mass is sufficiently peripheral and abuts the lung surface, percutaneous US-guided biopsy is a

safe and effective method for obtaining a tissue diagnosis.

•Congenital parenchymal masses include congenital pulmonary airway malformation (CPAM) and sequestration. Although often

regarded as separate entities, these malformations are part of a spectrum of

congenital pulmonary airway malformations and may have overlapping imaging and

histologic features.These masses may be detected prenatally by US or MR imaging,

appearing as variably solid or cystic structures.

•Postnatally, plain radiographs usually show the lesion, often as incidental findings or on images

taken for respiratory symptoms.• CPAMs have traditionally classified according to

their cystic component, although the usefulness of this is

•Questionable• .The US appearance follows this histologic

typing, demonstrating cysts of varying size amidst echogenic parenchyma (Fig. 21).

•Fig. 21. Congenital pulmonary airway malformation. (A) Longitudinal sonogram of the right chest in a newborn

•with prenatal diagnosis of a lung mass shows a complex mass with a large central cystic component

corresponding•to a type I CPAM. No normal lung was visualized. (B)

Longitudinal midline sonogram in another newborn•shows a large echogenic mass (M) representing a type

III CPAM. This mass displaces the heart (H) anteriorly•and to the left, and is inverting the diaphragm (arrow)

and displacing the liver (L) inferiorly.

•Although spontaneous regression of CPAMs has been reported, and there is controversy as to

whether surgery is indicated, most of these lesions are currently surgically resected in the United

States.

•Superimposed infection can pose difficulties and complications for surgery.

• Like lung abscesses, US-guided percutaneous drainage can allow successful treatment of infected CPAMs and allow a safer delayed surgical resection.

•Intralobar sequestrations are most often found in the lower lobes, presenting with recurrent

infections or persistent radiographic opacities.

• These are typically sonographically solid masses, although there may be cystic components .

•The key diagnostic feature of sequestration is demonstrating systemic arterial supply, usually

from the descending aorta (Fig. 22).

•Fig. 22. Congenital pulmonary sequestration with•cystic adenomatoid malformation. Coronal sonogram•of the inferior left chest shows an echogenic mass (M)•representing an intralobar sequestration with a large•feeding artery (arrow) arising from the thoracic aorta•(A .)Note the cystic components (arrowheads), which•were shown histologically to be elements of cystic

adenomatoid•malformation within the sequestration.

•Color Doppler sonography is diagnostically reliable in this condition in the neonate, infant, and young child, although

contrast-enhanced CT and MR imaging are often required in older patients with limited acoustic windows.

• Extralobar sequestrations have a separate pleural investment and are usually found in the inferior left chest but may even be

nlocated below the diaphragm where they may be confused with adrenal pathology.

• Patients present symptomatically at a younger age than those with

•intralobar malformation, with cyanosis and dyspnea more common.

• US features are similar in both conditions, although associated anomalies are more commonly associated with extralobar

sequestrations.

MEDIASTINUM•The thymus is the dominant noncardiac

mediastinal structure within the pediatric chest. Its appearance on chest radiography is

usually clear, although variations in size and position can occasionally be confusing and

prompt further imaging for clarification. The characteristic US appearance allows confident

diagnosis and obviates the need for further imaging tests (Fig. 23).

•Fig. 23. Prominent thymus. (A) Chest radiograph of an infant with respiratory symptoms shows an enlarged

cardiomediastinal•contour. (B) Transverse sonogram of the superior chest

shows a normal thymus (arrowheads) to be•the source of the radiographic findings. The thymus

conforms to the contours of the anterior chest wall and•drapes around the aorta (A) and pulmonary artery (PA).

Note the hypoechoic sternal cartilage with a small ossification

•center (S).

•Diminished thymic size is seen in infants and children subject to physiologic stress.

• DiGeorge syndrome is a cellular immunodeficiency disorder related to

hypoplasia or aplasia of the thymus.

• Although the associated anomalies are usually sufficient for diagnosis, failure to

visualize the infant thymus by US is strongly confirmatory.

•Primary thymic tumors in children are rare. Thymomas usually occur in older children and

adolescents, who often present with paraneoplastic syndromes.

• They can present as aggressive tumors particularly in cases of invasive thymomas.

• In this age group, mediastinal acoustic windows are more limiting. Therefore, MR imaging and

CT are often better imaging choices.

•Thymomas can be heterogeneous tumors with areas of necrosis and calcification,91,92

whereas thymolipomas are more homogeneously echogenic due to their fatty

content. Secondary neoplastic thymic infiltration is more common, and occurs

withleukemia, lymphoma, and Langerhans cell histiocytosis.

•In these cases, the normal sonographic thymic pattern is replaced with variably echogenic and

heterogeneous soft tissue and associated abnormal lobulation of the thymic capsule.

• Small calcifications have been described with histiocytic infiltration.

•An infiltrated thymus loses its normal compliance and may be seen to displace and distort adjacent

structures instead of conforming to their shape.

•The most common benign thymic masses are lymphatic malformations and thymic cysts.

•Lymphatic malformations are usually comprised of multiple loculated cysts with thin bands of intervening

soft tissue. Normally hypovascular,•lymphatic malformations may contain hemangiomatous

components that demonstrates flow with color Doppler.• Cysts contents are usually anechoic, but superimposed

hemorrhage or infection produces cyst contents of variable echogenicity or even fluid debris levels.

•Thymic cysts arise from remnants of the thymopharyngeal ducts,80 thymic tumors,

and cystic degeneration of the thymus itself associated with mediastinal trauma or

surgery.

• Most congenital cases of thymic cysts are diagnosed in childhood, presenting as slowly

enlarging masses that may extend into the neck.

•Thymic cysts typically are unilocular with imperceptible walls and anechoic contents,

and sonographic demonstration of their continuity with the thymus allows their

diagnosis.

• Thymic cysts associated with HIV infection are more commonly multiseptated and may

cause more diffuse thymic enlargement.

•The anterior mediastinum is a common site for other neoplasms, in particular lymphoma. The

majority of children with lymphoma have anterior mediastinal involvement, more frequent

withHodgkin lymphoma than with non-Hodgkin lymphoma.

• Patients may present with constitutional symptoms (fever and weight loss), respiratory

complaints (cough and dyspnea), and occasionally masses are discovered incidentally.

•Sonographically, lymphomas may appear as discrete masses, nodal enlargement, or with

diffuse thymic infiltration. They tend to be hypoechoic and hypovascular compared with inflammatory processes and other neoplasms

(Fig. 24).

•Fig. 24. Lymphoma. (A) Contrast-enhanced chest CT of a 14-year-old girl with fatigue

shows an anterior mediastinal•mass (M). (B) Longitudinal sonogram just

before percutaneous biopsy shows a predominantly hypoechoic

•mass (M) anterior to the mediastinal vessels (V). Core biopsies showed nodular sclerosing

Hodgkin disease.

•Teratomas and other germ cell tumors may also arise in the anterior mediastinum.

• The US appearance of germ cell tumors is variable, ranging from purely soft tissue

masses to heterogeneous masses containing fat, bone, and cystic elements (Fig. 25).

•Fig. 25. Anterior mediastinal teratoma. Transverse•sonogram of the chest in a newborn shows a

complex•solid and cystic mass (M) displacing the heart (H).•(Adapted from Coley BD. Pediatric chest

ultrasound.•Radiol Clin NorthAm2005;43:405–18; with

permission).

•A tissue diagnosis is required before chemotherapy, but airway compromise often

associated with large masses located within the anterior mediastinum may make surgical

biopsy undesirable.

• US-guided percutaneous biopsy is an excellent alternative in these patients and can

be don comfortably and safely, even in critically ill patients.

•Middle mediastinal lesions include cystic (bronchogenic, gastrointestinal, pericardial,

and lymphatic) and solid (lymphadenopathy) masses. Visualization of these masses with US

may become more difficult with increasing age of patients, but the optimal use of

acoustic windows can still make US a valuable diagnostic modality.

•Lymphadenopathy can arise from underlying neoplasia or infection, appearing abnormally enlarged and hypoechoic,

often with color Doppler hyperemia.100 Bronchogenic cysts are usually thin walled, whereas esophageal

duplication cysts may have a hypoechoic muscular rim typical of gastrointestinal duplications elsewhere in the

body; this differentiation may, however, be difficult.

•Pericardial cysts have a typical appearanc on plain radiographs, but US can confirm their cystic nature.

Lymphatic malformations in the mediastinum appear similar to those elsewhere in the body, as discussed

previously (Fig. 26).

•Fig. 26. Middle mediastinal lymphangioma. (A) Transverse sonogram using the heart as an acoustic window in

•a child with abnormal paraspinal widening on chest radiography shows a septated cystic mass (arrows)

posterior•to the heart (H) and anterior to the spine (S), surrounding

the aorta (A) and esophagus (E). (B) Transverse T2-•weighted MR imaging at a similar level with the same

findings. (Adapted from Coley BD. Pediatric chest ultrasound.

•Radiol Clin North Am 2005;43:405–18; with permission).

•Posterior mediastinal cystic masses include lymphatic malformations and neurenteric cysts, the

latter often associated with vertebral bodyanomalies.

• Most pediatric posterior mediastinal masses, however, are solid and arise from neural crest cells

within the sympathetic ganglion.

• In order of decreasing malignancy, these include neuroblastoma, ganglioneuroblastoma, and

ganglioneuroma.

•Posterior mediastinal masses can often be best visualized via a posterior thoracic or paraspinal approach. Although

sometimes containing calcifications, the sonographic•appearanceof these tumors isnonspecific.•Thoracic neuroblastomas commonly extend through neural

foramina, causing extradural compression of the spinal cord that may be symptomatic, and may be demonstrable

sonographically.•UScan also demonstrate neoplastic invasion of the chest

wall and bon involvement, although CT andMRimaging aremore commonly used and more sensitive than US.

DIAPHRAGM•US is a valuable tool in assessing the diaphragm, allowing delineation of

juxtadiaphragmatic masses, contour abnormalities and hernias,•and evaluation of diaphragmatic motion.

•Congenital diaphragmatic hernias are typically located on the left and usually pose little diagnostic confusion on plain radiographs. When

radiographic findings are less clear, especially with right-sided hernias, US becomes a useful modality for confirmation and furthe characterization.

•Sagittal and coronal scanning allows depiction of the diaphragm and assessment its integrity.

•Discontinuity of the diaphragm is readily seen, and the herniated viscera can be evaluated

•(Fig. 27.)

•Fig. 27. Right-sided congenital diaphragmatic hernia.

•Sagittal sonogram through the inferior right chest of

•an infant with radiographic opacity of unclear•etiology shows a defect (arrow) in the hypoechoic•muscular right hemidiaphragm (arrowheads) with•herniation of liver (L) into the chest.

•Eventration of the diaphragm results from a congenital weakness or thinness of the central

tendon or muscle• Patients may present with respiratory difficulties,

but the radiographic findings are often incidental. Although further imaging may not be required, US

can confirm the diagnosis by demonstrating an intact hemidiaphragm, thus helping to exclude

contained hernias or masses (Fig. 28).

•Fig. 28. Diaphragmatic eventration. Longitudinal•sonogram of the right upper abdomen in a young•child with a diaphragmatic contour abnormality on•chest radiographs shows an intact diaphragm with•a focal eventration (arrowheads) with liver (L)•protruding superiorly.

•Elevation of a hemidiaphragm after thoracic surgery raises the question of diaphragmatic paresis or paralysis.

• US provides a portable method for evaluating diaphragmatic motion without the use of radiation.

Sagittal or coronal imaging provides information about that particular hemidiaphragm, whereas transverse

imaging allows comparison of both hemidiaphragms and evaluation for paradoxic motion with unilateral paralysis

(Fig. 29).•With M-mode recording, US can provide quantitative

information about diaphragmatic excursion.

•Fig. 29. Diaphragmatic paralysis. Transverse sonogram of the chest in an infant with a

persistently elevated right•hemidiaphragm after cardiac surgery. (A) In

expiration the right hemidiaphragm (arrows) is higher than the left

•(arrowheads( .)B )With inspiration there is expected inferior displacement of the left hemidiaphragm

(arrowheads)•but no motion of the right hemidiaphragm (arrows).

CHEST WALL•Abnormalities of the pediatric chest wall are

particularl amenable to high-resolution sonography. Nonpainful soft tissue masses are

usually benign, and sonography often provides a definitive diagnosis.

• Cystic and vascular masses are more often benign than solid masses.

•US can accurately assess the extent and depth of lesions, which are important if surgical

resection is considered• .Doppler evaluation can help characterize the

type of vascular malformation, which can be useful in determining an efficacious

treatment. Common benign chest wall masses include vascular and lymphatic malformations,

lipomas, and lymph nodes.

•Hemangiomas and other vascular lesions usually have discoloration of the overlying skin, providing

the first clue to diagnosis .

•On grayscale imaging, hemangiomas are variably echogenic depending on the amount of fatty

stroma and are typically well circumscribed .

•Hemangioma usually have high Doppler frequency shifts and high color Doppler vessel density,

whereas other vascular malformations do not (Fig. 30).

•Fig. 30. Chest wall hemangioma. (A) Transverse color Doppler sonogram in a 5-year-old child with a soft palpable

•mass shows heterogeneous ovoid mass with marked vascularity that was arterial on pulsed Doppler

interrogation.•The mass is superficial to the intercostal musculature

(arrowheads). (B) Contrast-enhanced CT shows intense•enhancement within the hemangioma (arrow) and

redemonstrates its location relative to the intercostal muscles

•(arrowheads .)Given the child’s age, this represents a noninvoluting congenital hemangioma.

•Venous malformations have a more bluish discoloration of the skin and show multiple serpiginous

channels and cystic spaces.• Blood flow may be too slow to produce pulsed or

color Doppler signal but with gentle compression and release the slow inflow of blood can be detected.

Lymphatic malformations have variably sized cystic components whose echogenicity depends on whether

there has been infection or hemorrhage into the normally anechoic cyst fluid .

•They may be found anywhere in the chest but are most common in the axilla

•(Fig. 31.)

•Fig. 31. Lymphatic malformation. Transverse sonogram

•of the axilla in a teenage girl with swelling•and skin discoloration shows a mixed cystic

lesion.

•There are anechoic cysts (arrow) along with echogenic

•cysts (asterisks) from internal hemorrhage that•demonstrate fluid levels (arrowheads).

•Extension and infiltration into the mediastinum is common and may necessitate MR imaging for complete

evaluation. Treatment may be surgical excision, although less invasive percutaneous sclerotherapies are effective

and have less morbidity.•Neurofibromas may arise along costal margins within the

neurovasvular bundle. Lipomas are generally well-circumscribed masses usually located within the

subcutaneous tissues•.•They are typically echogenic due to their fat content but

may be less echogenic than fat elsewhere in the body

•Color Doppler flow minimal. Lymph nodes are usually recognizable by their echogenic fatty

hila containing the central nodal blood supply, although inflamed and infiltrated nodes may

have distorted internal architecture and color Doppler flow. to lipomas is

•Firm, nontender masses may be secondary to bony or cartilaginous anomalies.

• Bony abnormalities are often detectable by plain radiographs, but US can clarify and confirm findings.

Anomalous rib ends can be diagnosed.• Osteochondromas and their cartilaginous

components can be assessed and followed.• Anterior chest wall irregularities are often due to

asymmetric cartilaginous costochondral junctions,110 readily visible sonographically

•(Fig. 32.)

•Fig. 32. Bifid rib. Transverse sonogram over an area of

•painless chest wall asymmetry in a 12-year-old girl

•shows a bifid anterior rib with two costosternal cartilages

•(C ,)a normal variant

•Traumatic separation of the costochondral cartilage from rib ends has been reported in child abuse, a finding visible

sonographically but not with plain radiographs .•Rib fractures are common after trauma, but radiographic

detection may be difficult if there is little fragment displacement.

• Sonography easily shows the disruption of the rib’s cortical surface, and there maybe an adjacent hematoma

or callous formation depending on the age of the injury (Fig. 33).

•Fig. 33. Rib fracture. Longitudinal sonogram along

•a painful rib after a football injury shows cortical

•discontinuity (arrow) and a small associated hematoma

•(arrowheads )of a radiographically occult rib•fracture.

•Sternal fractures are also readily detected with nUS113 with greater sensitivity and

specificity than plain radiographs.

• Costosternal osteocartilaginous injuries can also be seen in children after pectus

excavatum surgery.

•Malignant chest wall lesions are uncommon in children but include Askin tumor (primitive neuroectodermal tumor of

the chest wall) and rhabdomyosarcoma. Echogenicity of these malignant chest wall lesions is variable .

•The margins of these lesions may be distinct or infiltrative. Color Doppler flow of malignant chest wall lesions is usually

increased.

•Chest wall and rib invasion can be detectedas interruption of the normal muscular layers of the chest wall and loss of

the normally smooth bony cortical surface (Fig. 34).

•Fig. 34. Askin tumor. (A) Chest radiograph of an 11-year-old girl referred to interventional radiology for drainage

•of a presumed left parapneumonic effusion. Note the 10th posterior rib erosions (arrowheads) not recognized at

•the referring clinic. (B) Transverse intercostal sonogram shows a large mass (M) protruding form the chest wall

•into the thorax and an associated effusion (E). Percutaneous biopsy was performed and revealed Askin

tumor.•(C )Subsequent contrast-enhanced CT confirms the chest

wall origin of the mass (M) with associated rib destruction•(arrow.)

•As with most other imaging, US is not histologically specific, and some benign

lesions (such as abscesses and hematomas) may have aggressive sonographic

appearances (Fig. 35) .

•Tissue sampling, often via US-guided biopsy, is usually needed for a definitive diagnosis.

•Fig. 35. Rib osteomyelitis. (A) Transverse color Doppler sonogram of a teenage boy with right anterolateral chest

•wall pain and swelling shows destruction of the rib (R) with a large hyperemic mass. (B) Axial contrast-enhanced

•T1-weighted MR imaging with fat saturation shows the rib ending in a complex mass (arrowheads) with an

•enhancing rim and septations the produces mass effect on the liver (L). Subsequent aspiration and biopsy yielded

•methicillin-resistant Staphylococcus aureus.

VESSELS•Advances in contrast MR imaging and CT

angiography allow superb depiction of the thoracic vasculature. Deep structures, such as the superior vena cava and thoracic aorta, are

difficult to evaluate sonographically in older pediatri patients, but US remains a principle method of investigation of vascular disease

particularly within the subclavian and jugular vessels.

•The most common indication for vascular US is the evaluatio of suspected venous thrombosis. Acute

thrombosis often occurs in association with an indwelling vascular catheter and/or malignancy

and appears as hypoechoic material expanding the vessel lumen

• .Because compression of the subclavian and deeper thoracic veins is not possible, color and

pulsed Doppler areimportant in confirming thrombosis.

•Depending on patient size and anatomy, it may be difficult to directly interrogate medial

portions of the subclavian and brachiocephalic veins, and indirect Doppler findings of venous stenosis or occlusion may have to be relied on.

• Having no valves, the central thoracic veins show the effects of cardiac and respiratory

activity, with marked phasicity and even reversal of flow with atrial systole.120

•With central venous occlusion or stenosis, this phasicity is lost or dampened, and

interrogation of more lateral segments of the subclavian vein can thus indicate a more central location of abnormality (Fig. 36).

•Fig. 36. Superior vena cava stenosis. (A) Duplex Doppler sonogram of the right brachiocephalic vein

just cephalad•of the superior vena cava in a 1-year-old child with

upper extremity swelling after heart transplantation shows

•a patent vessel but with dampening of transmitted cardiac pulsations. (B) Coronal contrast-enhanced

CT image•shows stenosis of the superior vena caval

anastomosis (arrow).

•Investigation of both sides is often helpful in uncovering subtle flow differences that may

indicate abnormalities.

• With chronic occlusion, collaterals may become large and give the appearance of

normal native vessels. Doppler flow seldom appears normal, however, and typically is dampened and more monophasic than in

normal vessels.

•Arterial stenoses and aneurysms may occur from trauma, vascular access complications, or one of the arteritides.

Inadvertent arterial puncture during line placement can lead to vessel injury or rarely arteriovenous fistula formation.

• Doppler can detect the abnormal high diastolic arterial flow in arteriovenous fistulas and the elevated and turbulent

venous flow. Hyperextension injuries or penetrating trauma can cause intimal disruptions, leading to subclavian arterial

occlusion or stenosis.• Thoracic arterial stenoses, like those elsewhere in the body,

are detectable by elevation of peak systolic flow through the stenosis, delayed systolic upstroke distal to the stenosis, and

elevated diastolic flow due to downstream vasodilatation.

•Thoracic outlet syndrome produces neurologic or vascular symptoms from compression of neurovascular

structures in the upper chest.• Anomalous cervical or first thoracic ribs, the anterior

scalene muscle, and vascular variants may all contribute and may be seen by US.

• MR imaging provides exquisite anatomic detail of the thoracic outlet, but duplex US may provide important

physiologic information by demonstrating alterations in arterial and/or venous flow, especially during

reproduction of the position in which symptoms occur.

•Arterial flow may show acceleration or dampening of flow, depending how proximity to

the stenotic segment.• Venous flow is more commonly affected, and

there may be engorgement of the lateral subclavian and axillary veins and loss of

transmitted cardiac waveforms.•Thrombosis may complicate repetitive venous

compression, such as in cases of Paget-Schroetter syndrome, which is readily diagnosable

•by US.