Comparison of Ultrasound And

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1648 AJR:193 , December 200 9

and is often required before surgery to char-

acterize anatomy and evaluate for coexisting

pulmonary abscess [3].

In light of increasing awareness of radiation

exposure risks, particularly in children, we

retrospectively compared the information ob-

tained from chest ultrasound and chest CT in

children with pneumonia and parapneumonic

effusion to determine if chest ultrasound could

serve as a useful alternative to chest CT. In

those patients who underwent surgical man-

agement, operative findings were reviewedand correlated with imaging findings.

Materials and Methods

Patient Population

The study met requirements for exemption

from institution review board approval. Children

diagnosed with complicated pneumonia (pneu-

monia and effusion) on the basis of clinical ex-

amination and chest radiography, who underwent

both chest CT and chest ultrasound during their

Comparison of Ultrasound and

CT in the Evaluation of PneumoniaComplicated by ParapneumonicEffusion in Children

Jessica Kurian1

Terry L. Levin1

Bokyung K. Han2

Benjamin H. Taragin1

Samuel Weinstein3

Kurian J, Levin TL, Han BK, Taragin BH,Weinstein S

1Department of Radiology, Albert Einstein College of

Medicine and Montefiore Medical Center, 111 E 210th St.,

Bronx, NY 104 67. Address correspondence to T. L. Levin

([email protected]).

2Department of Radiology, Mount Sinai Medical Center,

New York, NY.

3Department of Pediatric Cardiothoracic Surgery, Albert

Einstein College of Medicine and Montefiore Medical

Center, Bronx, NY.

Pediatr ic Imaging Original Research

AJR2009; 193:16481654

0361803X/09/19361648

American Roentgen Ray Society

Community-acquired pneumonia in the

pediatric population is common, with 40

cases per 1,000 children under 5 years old

diagnosed annually in Europe and North

America [1]. Up to 53% of hospitalized cas-

es are complicated by parapneumonic effu-

sion, empyema, and pulmonary necrosis or

pulmonary abscess [2]. Both the diagnosis

and therapy of complicated pneumonia are

guided by imaging. Although initial evalu-

ation is based on chest radiography, chest

CT has traditionally been used to evaluatethe disease process in children before chest

tube drainage (with or without thrombolyt-

ics), video-assisted thoracoscopy (VAT), or

open thoracotomy and decortication. The

British Thoracic Society (BTS) guidelines

for the management of pediatric empyema

recommend the use of chest ultrasound for

detecting pleural effusion and guiding drain

placement. However, the guidelines note that

chest CT plays a role in complicated cases

Keywords:CT, empyema, parapneumonic effusion,

pediatric, pneumonia, ultrasound

DOI:10.2214/AJR.09.2791

Received March 24, 200 9; accepted after revision

May 16, 200 9.

Presented at the 200 9 annual meeting of the Society of

Pediatric Radiology, Carlsbad, CA.

OBJECTIVE.The purpose of our study was to compare chest ultrasound and chest CT in

children with complicated pneumonia and parapneumonic effusion.

MATERIALS AND METHODS.We retrospectively compared chest ultrasound and

chest CT in 19 children (nine girls and 10 boys; age range, 8 months17 years) admitted with

complicated pneumonia and parapneumonic effusion between December 2006 and January

2009. Images were evaluated for effusion, loculation, fibrin strands, parenchymal consolida-

tion, necrosis, and abscess. In the subset of patients who underwent surgical management, im-aging findings were correlated with operative findings.

RESULTS.Eighteen of 19 patients had an effusion on both chest ultrasound and chest

CT. The findings of effusion loculation as well as parenchymal consolidation and necrosis or

abscess were similar between the two techniques. Chest ultrasound was better able to visual-

ize fibrin strands within the effusions. Of the 14 patients who underwent video-assisted tho-

racoscopy, five had surgically proven parenchymal abscess or necrosis. Preoperatively, chest

ultrasound was able to show parenchymal abscess or necrosis in four patients, whereas chest

CT was able to show parenchymal abscess or necrosis in three.

CONCLUSION.In our series, chest ultrasound and chest CT were similar in their abil-

ity to detect loculated effusion and lung necrosis or abscess resulting from complicated pneu-

monia. Chest CT did not provide any additional clinically useful information that was not

also seen on chest ultrasound. We suggest that the imaging workup of complicated pediatric

pneumonia include chest radiography and chest ultrasound, reserving chest CT for cases in

which the chest ultrasound is technically limited or discrepant with the clinical findings.

Kurian et al.Ultrasound and CT in Evaluation of P neumonia

Pediatric ImagingOriginal Research


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AJR:19 3, December 200 9 1649

Ultrasound and CT in Evaluation of Pneumonia

admission between December 2006 and January

2009 were included in the study. Nineteen pa-

tients (nine boys and 10 girls) with a mean age of

5.4 years (age range, 8 months17 years) who met

the study criteria were identified. The mean time

between chest ultrasound and CT was 2.7 days

(range, 08 days).

Chest Ultrasound Technique

Chest ultrasound was performed by two expe-

rienced staff ultrasound technologists on an iU22

ultrasound system (Philips Healthcare) (n= 15),an HDI 5000 ultrasound system (Philips Health-

care) (n= 3), or an Acuson Sequoia 512 ultra-

sound system (Siemens Healthcare) (n= 1). Lin-

ear (512 MHz), curved linear (25, 49, or 58

MHz), and vector (58 MHz) transducers were

used. The chest abnormality was localized on

the basis of chest radiography findings. Anteri-

or, posterior, and midaxillary images were ob-

tained using an intercostal approach in transverse

and longitudinal planes from the apex to the dia-

phragm with the patient in a supine or decubitus

position. Color Doppler ultrasound was performed

to evaluate the vascularity of regional parenchy-mal abnormalities.

Chest CT Technique

Chest CT was performed on an MX-8000 IDT

16-MDCT scanner (Philips Healthcare) (n= 7), a

Brilliance 16-MDCT scanner (Philips Healthcare

Electronics) (n = 6), or a LightSpeed VCT 64-

MDCT scanner (GE Healthcare) (n= 5). Images

were obtained from the level of the thoracic inlet

to the diaphragm using a pitch of 1.0, 120 kVp, and

a weight-based low-dose tube current. Thirteen of

the patients underwent CT with the administration

of nonionic IV contrast material (320 mg I/mL io-

dixanol, Visipaque, GE Healthcare) at a dose of

1 mL/kg. CT data were reconstructed at a slice

thickness of either 3 or 5 mm for image review.

For one patient, images from an unenhanced chest

CT performed at an outside hospital on the day of

transfer to our institution were reviewed.

Image Evaluation

The chest CT and chest ultrasound images were

retrospectively reviewed in consensus by a board-

certified pediatric radiologist and a radiology resi-

dent. The interpreting radiologists were blinded to

the results of the chest CT and chest ultrasound

when reviewing either study. Images were exam-

ined for the presence of pleural effusion and fibrin

strands within the effusion. Pleural effusion was

defined as loculated if the collection had a lobulat-

ed or lenticular shape with a convex border [4, 5].

Chest CT and chest ultrasound images were

also examined for parenchymal consolidation and

the presence of lung necrosis or abscess. On chest

CT, consolidation was defined as air-space opac-

ity with air bronchograms. On chest ultrasound, it

was defined as replacement of normal reflectionsof aerated lung by solid-appearing areas, with

A

Fig. 13-year-old boy with pneumonia and loculated effusion.Aand B,Axial contrast-enhanced chest CT image (A) and longitudinal image from chest ultrasound (B) show

loculated pleural effusion (cursors) with lobulated shape and convex margin. Although pleural fluid appearsinhomogeneous on chest CT, numerous fibrin strands are better visualized on chest ultrasound (arrows, B).

B

A

Fig. 24-year-old boy with pneumonia and empyema.AC,Axial contrast-enhanced chest CT image (A) and longitudinal image from chest ultrasound (B) show parapneumonic effusion. Fibrin strands within pleural fluid areseen to advantage on chest ultrasound (arrows, B) and correlate with intraoperative findings (C) of empyema and fibrin stranding.

B C


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1650 AJR:193 , December 200 9

Kurian et al.

bright linear and branching echoes representing

sonographic air bronchograms [6, 7]. On chest CT,

pulmonary necrosis was assessed on contrast-en-

hanced scans and was defined as a low-density area

within a consolidated lung that had diminished en-

hancement relative to the adjacent parenchyma [4,

8]. On chest ultrasound, pulmonary necrosis was

defined as a focal rounded area of decreased echo-

genicity within a portion of consolidated lung [9].

Although the use of color Doppler ultrasound in the

evaluation of necrotizing pneumonia has not been

well studied, a lack of central color Doppler flow

within the hypoechoic pulmonary lesions was used

to support the diagnosis of necrosis because it has

been suggested that necrosis is related to areas of

ischemic lung arising from adjacent inflammation

[8]. Abscess was defined as an intrapulmonary cav-

ity containing fluid or air, with no central enhance-

ment on chest CT or no central color Doppler flow

on chest ultrasound [4, 10].

Surgical Correlation

In addition to antibiotics, therapeutic options

for the treatment of pneumonia complicated by ef-

fusion include chest tube placement with instilla-

tion of fibrinolytics into the pleural space, or VAT

[11, 12]. At our institution, VAT is the preferred

method in patients who fail antibiotic therapy ei-

ther with or without chest tube drainage. Typical-

ly, the decision to proceed to surgery is based on

assessment of the patient by a surgeon in conjunc-

tion with a multidisciplinary clinical team. Labo-

ratory and radiologic data are taken into account.

For the patients in our study who were managed

surgically, operative and histopathology reports

were reviewed for the presence of pleural fluid,

empyema, and lung necrosis or abscess. The chest

CT and chest ultrasound findings were compared

with operative findings.

Results

Pleural Findings

Of the 19 patients in whom pneumonia

with parapneumonic effusion was diagnosed

on chest radiography, 18 had an effusion con-

firmed on both chest CT and chest ultra-

sound, and one had no effusion on either ex-

amination. Fifteen effusions were loculated

on chest CT, and 13 were loculated on chest

ultrasound; in one patient, loculation seen on

chest CT could not be determined on chest

ultrasound because of scan quality limita-

tions. Fibrin strands were identified in all pa-

tients with effusion on chest ultrasound except

for one patient with only trace fluid; some

patients showed few fibrin strands, whereas

others showed numerous strands of variable

A

Fig. 37-year-old girl with pulmonary necrosis due to complicated pneumonia.A,Axial contrast-enhanced chest CT image shows loculated effusion, with adjacent consolidated lungcontaining multiple areas of diminished enhancement.B,Findings from Acorrespond to focal, round echo-poor lesions on longitudinal chest ultrasound image(arrows). Lesions show some peripheral but no central color Doppler flow.

B

A

Fig. 42-year-old boy with complicated pneumonia and surgically proven lung abscess.A,Chest radiograph shows abnormal collection of air (arrows).B,Axial contrast-enhanced chest CT image shows that abnormal collection of air seen in Acorresponds to abscess (arrowheads).C,Transverse chest ultrasound image shows abscess as amorphous collection of fluid and air (asterisk) within lung. Hyperechoic line (arrow) represents airfluidinterface.

B C


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1652 AJR:193 , December 200 9

Kurian et al.

thickness. Although presumably present, fi-

brin strands could not be clearly delineated on

any of the chest CT images (Figs. 1 and 2).

Parenchymal Findings

Of the 19 chest CT examinations, 13

were contrast-enhanced and six were unen-

hanced. All chest CT examinations showedparenchymal consolidation.The contrast-en-

hanced examinations identified six patients

with coexisting necrosis and two with coex-

isting abscess. Of the 19 chest ultrasound ex-

aminations, 18 showed parenchymal consoli-

dation. Six of these had coexisting necrosis,

and one had a coexisting abscess.

Consolidation was shown in all patients

on both chest CT and chest ultrasound except

for one chest ultrasound in which technical

limitations precluded evaluation of the lung.

Chest CT and chest ultrasound concurred on

the presence of necrosis in five patients (Fig.

3) and differed in two; necrosis was identi-

fied on chest CT in one patient for whom the

ultrasound was limited by lack of evaluation

with a linear transducer (patient 17, Table 1),

and necrosis was identified on chest ultra-

sound in another patient for whom the chest

CT was unenhanced (patient 12, Table 1).

Surgical Findings

Fourteen patients underwent VAT, and five

were treated with antibiotics with or without

chest tube drainage. In the surgically man-

aged group, 13 patients were found to have

empyema; of these, five also had pulmonaryabscess or necrosis, and one was found to

have underlying cystic lung disease.

Loculation seen preoperatively on chest

ultrasound or chest CT correlated with the

presence of empyema in 12 of the 13 patients

(12 loculated effusions on chest CT and 11

on chest ultrasound). One patient with empy-

ema did not have loculation on either imag-

ing examination but did have fibrin stranding

on chest ultrasound. All patients with em-

pyema had debris and fibrin strands within

pleural fluid on chest ultrasound.

Of the five patients with parenchymal ab-

scess (Fig. 4) or necrosis at surgery, either ne-crosis or abscess was seen preoperatively on

chest ultrasound in four patients and on chest

CT in three patients (in one patient, necrosis

could not be determined on an unenhanced

chest CT).

There was one false-negative imaging di-

agnosis in which a surgically diagnosed ab-

scess was not seen on either chest ultrasound

or chest CT (patient 6, Table 1).

There were two false-positive parenchy-

mal diagnoses. In one patient, an abscess was

identified on chest CT but not chest ultra-

sound, and abscess was not confirmed at sur-

gery (patient 8, Table 1 and Fig. 5). In another

patient, necrosis was diagnosed on both chest

ultrasound and chest CT, and at surgery un-

derlying cystic lung disease without necrosiswas seen (patient 10, Table 1 and Fig. 6).

There were no cases in which a surgical-

ly confirmed parenchymal abnormality was

seen preoperatively on chest CT but not also

seen on chest ultrasound.

Discussion

No consensus exists on the optimal tech-

nique for imaging complicated pneumonia in

children. In many centers, patients routine-

ly undergo chest CT for characterization of

pleural effusion and underlying parenchymal

disease before chest tube placement or sur-

gery for drainage and decort ication. Although

chest CT allows rapid image acquisition, the

rising use of CT in the pediatric population

raises the concern of an increasing ionizingradiation burden. Because the risk of radia-

tion-induced cancer in children from medical

imaging is estimated to be as high as one in

500 [13], it is incumbent on the radiologist to

investigate alternative imaging strategies.

Few studies have compared the efficacy of

chest ultrasound and chest CT in patients with

complicated pneumonia and parapneumonic

effusion. Prior investigations in both children

C

Fig. 54-year-old boy with complicated pneumonia and false-positive diagnosis of lung abscess on chest CT.AD,Contrast-enhanced axial CT images with mediastinal ( A) and lung (B) windows and coronal (C) andsagittal (D) CT images with lung windows show air-filled collection in right hemithorax. Initially interpretedas intrapulmonary, this collection may have represented loculated pleural air in major fissure because nopulmonary abscess was identified at surgery. Collection was not identified on preoperative chest ultrasound,possibly due to acoustic shadowing from air in pleural space.

D

A B


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AJR:19 3, December 200 9 1653

Ultrasound and CT in Evaluation of Pneumonia

[14, 15] and adults [16, 17] have focused pri-

marily on the ability of chest ultrasound or

chest CT to correlate with effusion stage or

to predict clinical outcome and have shown

variable results. Neither chest ultrasound nor

chest CT has been shown to accurately pre-

dict effusion stage [5]. Most recently, Jaffe

et al. [4] compared chest CT and chest ultra-sound in 31 children with complicated pneu-

monia and found only a weak correlation in

effusion scores. The study did not include a

comparison of parenchymal findings.

Our results concur with reports published

previously on the use of chest ultrasound in the

evaluation of parapneumonic effusion [3, 5].

Although chest ultrasound may be limited by

its small field of view and shadowing of deep

structures by overlying air, we found that it was

equally able to detect pleural fluid and locula-

tion when compared with chest CT. Chest ultra-

sound was superior to chest CT in its ability to

resolve the internal components of pleural flu-

id including fibrin strands, which may indicate

early organization of an effusion [7]. In our

study, loculation seen on chest CT was also

seen on chest ultrasound in all patients except

one, in whom a delay between the chest ultra-

sound and chest CT may have allowed time for

the effusion to become more organized. In the

subset of patients who underwent VAT, all but

one patient with surgically confirmed empye-

ma showed loculated fluid on both chest ultra-

sound and chest CT when performed within a

few days of each other, and all showed fibrin

stranding on chest ultrasound.

The most recent BTS recommendations

encourage the use of chest ultrasound to con-

firm the presence of pleural effusion, but the

guidelines note that contrast-enhanced chest

CT is useful for evaluation of advanced pa-

renchymal disease [3]. This can be clinically

significant because the presence of necrotiz-

ing pneumonia requires a prolonged courseof antibiotics [5]. However, in our patient

group, chest ultrasound was similar to con-

trast-enhanced chest CT in its ability to di-

agnose pulmonary consolidation, lung ne-

crosis, and abscess. Except for one patient in

whom the chest ultrasound was technically

limited, pulmonary consolidation identified

on chest CT was also seen on chest ultra-

sound. Chest CT and chest ultrasound con-

curred on the presence of pulmonary necro-

sis except in two patients, including one in

whom the chest ultrasound was limited by

technique and one in whom the chest CT was

performed without IV contrast administra-

tion. In the subset of patients who underwent

VAT, there were no parenchymal abnormali-

ties found at surgery that were seen on chest

CT but not also seen on chest ultrasound.

Two false-positive imaging diagnoses

were identified. In one patient, an abscess

was diagnosed on chest CT but not on chest

ultrasound, and no abscess was identified at

surgery. On further review of the case, the

amorphous collection of air initially inter-

preted as an abscess on chest CT may have

represented loculated pleural air within the

major fissure in this patient who had a sus-

pected bronchopleural fistula (Fig. 5). The

process was not appreciated on chest ultra-

sound, possibly because of acoustic shadow-

ing from air within the pleural space. In an-

other patient, lung necrosis shown on both

chest ultrasound and chest CT correspond-

ed to an area of soft and cystic lung at sur-

gery, without true necrosis and without em-pyema (Fig. 6). A preexisting lung anomaly

was postulated.

This study is limited by its small sample

size. Additionally, the chest ultrasound images

were not evaluated in real time because of the

retrospective nature of the investigation. We

also acknowledge that, whereas acquisition of

chest CT can be standardized by machine set-

tings, the technical quality of chest ultrasound

was more variable in our sample. Of note, im-

ages obtained with a linear transducer ap-

peared to be superior to those obtained with

a vector transducer in detecting both pleural

and parenchymal abnormalities.

In this series of children with pneumo-

nia complicated by parapneumonic effu-

sion, chest ultrasound provided data simi-

lar to chest CT in the evaluation of pleural

fluid as well as the assessment of underly-

ing parenchymal consolidation, necrosis, or

abscess. Chest CT did not provide any ad-

ditional clinically useful information that

was not also seen on chest ultrasound. The

benefits of chest ultrasound over chest CT

include its portability, absence of need for

patient sedation, and superior ability to de-

tect fibrin strands within an effusion, whichcorresponded to the presence of empyema

in our study group. In accordance with the

as low as reasonably achievable principle of

minimizing radiation exposure, we suggest

that the evaluation of children with compli-

cated pneumonia include chest radiography

and chest ultrasound. Chest CT may be re-

served for patients in whom chest ultrasound

is technically difficult or discrepant with the

clinical findings.

Acknowledgment

We thank Betsy Castillo for her help in

performing chest ultrasound.

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A

Fig. 611-month-old girl with cystic lung anomaly seen at surgery and false-positive diagnosis of pulmonarynecrosis on preoperative imaging.A,Axial contrast-enhanced chest CT shows rounded areas of decreased parenchymal enhancement (arrows)as well as lobulated collections of air.B,Transverse chest ultrasound image shows rounded hypoechoic areas in left lower lobe (arrows). Chest CTand chest ultrasound findings were misinterpreted as areas of necrosis. At surgery, lesions were soft andcystic, but no necrotic material or pus could be aspirated and no empyema was present.

B


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F O R Y O U R I N F O R M A T I O N

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Comparison of Ultrasound And