Evaluation of lung ultrasound for the diagnosis of
pneumonia in the ED
Stefano Parlamento MDa,⁎, Roberto Copetti MDa, Stefano Di Bartolomeo MDb
aEmergency Department, S. Antonio Abate Hospital, 33028 Tolmezzo, Italy
bUnit of Hygiene and Epidemiology, University of Udine, 33100 Udine, Italy
Received 6 December 2007; revised 19 February 2008; accepted 4 March 2008
Objectives: The aim of this study is to assess the ability of bedside lung ultrasound (US) to confirm
clinical suspicion of pneumonia and the feasibility of its integration in common emergency department
(ED) clinical practice.
Methods: In this study we performed lung US in adult patients admitted in our ED with a suspected
pneumonia.Subsequently, a chest radiograph (CXR) was carried out for each patient. A thoracic
computed tomographic (CT) scan was made in patients with a positive lung US and a negative CXR. In
patients with confirmed pneumonia, we performed a follow-up after 10 days to evaluate clinical
conditions after antibiotic therapy.
Results: We studied 49 patients: pneumonia was confirmed in 32 cases (65.3%). In this group we had
31 (96.9%) positive lung US and 24 (75%) positive CXR. In 8 (25%) cases, lung US was positive with a
negative CXR. In this group, CT scan always confirmed the US results. In one case, US was negative
and CXR positive. Follow-up turned out to be always consistent with the diagnosis.
Conclusion: Considering that lung US is a bedside, reliable, rapid, and noninvasive technique, these
results suggest it could have a significant role in the diagnostic workup of pneumonia in the ED, even if
no sensitivity nor specificity can be inferred from this study because the real gold standard is CT, which
could not be performed in all patients.
© 2009 Elsevier Inc. All rights reserved.
Community-acquired pneumonia (CAP) in adults is a
common disorder, potentially life threatening , with a high
hospitalization rate . It is the only acute respiratory tract
infection in which delayed antibiotic therapy has been
associated with increased risk of death . Therefore, a
correct and rapid diagnosis is mandatory.
Currently, chest radiograph (CXR) is recommended for
the routine evaluation of a patient suspected of having
pneumonia because medical history and physical examina-
tion cannot provide certainty in this diagnosis . However,
especially in the emergency department (ED) setting, CXR
might have many limitations due to patient conditions, waste
of time, and interobserver variability in its interpretation .
Computed tomography (CT), on the other hand, is
considered to be the gold standard technique, but it is often
not available, has high radiation dose, and has high cost .
Lungs are traditionally considered poorly accessible to
ultrasound (US) investigation because of their air content .
Only in the last decade, it has been shown that the US
assessment of the lung could have a role in common clinical
⁎Corresponding author. Tel.: +39 3281186109.
E-mail address: email@example.com (S. Parlamento).
0735-6757/$ – see front matter © 2009 Elsevier Inc. All rights reserved.
American Journal of Emergency Medicine (2009) 27, 379–384
In lung consolidations, air is replaced by fluid, leading to
a good US transmission if there is a direct contact of the
lesion with pleural surface [9,10]. Not many studies were
performed in the last years for the evaluation of lung US in
the diagnosis of infectious lung diseases [11-15].
The aim of this study is to assess the ability of bedside
lung US to confirm clinical suspicion of pneumonia and the
feasibility of its integration in common ED clinical practice.
The study was conducted in the ED of S. Antonio Abate
Hospital, Tolmezzo, Italy, a second-level general hospital,
during a 4-month period (from October 4, 2006, to January
15, 2007). This ED usually has about 20 000 visits per year.
2.2. Inclusion criteria
Patients not consecutively admitted to our ED with signs
and symptoms of CAP were studied. According to the
international guidelines [16-19], the suggestive clinical
elements were cough, fever or dyspnea, sputum production,
and pleuritic chest pain. In elderly (N75 years), altered mental
status, failure to thrive, and falls were also considered.
Patients were admitted from Monday to Friday, in the
daytime (from 8:00 AM to 8:00 PM). The presence of the
expert in lung US was necessary for patient enrollment.
2.3. Exclusion criteria
We excluded children (b16 years old) and pregnant
women because of the restrictions in the use of CT required
for these patients. We also excluded patients with respiratory
insufficiency associated with vomiting, because of the cli-
nical suspicion of aspiration pneumonia, due to the pecu-
liarity of this condition.
In patients with history and examination suggestive of
pneumonia (Fig. 1), one unblinded emergency physician
(30 years experienced in general and cardiac US and 10 years
trained in lung US) performed all the lung US examinations.
Chest radiography was always carried out after US. A
positive CXR was considered sufficient for the diagnosis,
irrespective of US results. On the other hand, a positive lung
US and a negative CXR called for CT, according to
preexisting protocols. Chest radiography and CT scans
were read by the senior radiologist on duty, aware of the
clinical suspicion but not of the US findings. Before the CT, a
second blinded radiologist confirmed the CXR findings.
In all patients with confirmed pneumonia, we performed a
10-day follow-up to verify clinical and laboratory improve-
ment of patients after antibacterial therapy (Fig. 1). We ob-
tained informed consent only from patients undergoing CT
Statistical analysis was done using k statistic and
McNemar tests to assess concordance and symmetry
between lung US and CXR results.
2.6. Instrumental examinations
A convex 3.5- to 5-MHz probe (Megas CVX, Esaote
Medical Systems, Firenze, Italy) was used. At bedside, the
probe was set perpendicular, oblique, and parallel to the ribs
in the anterior, lateral, and posterior (lower and upper)
thorax. Sitting position and lateral decubitus were used to
scan the posterior chest wall.
In agreement with literature [9,20,21], each hemithorax
was divided into 5 areas: 2 anterior, 2 lateral, and 1 posterior.
The anterior chest wall was marked off from parasternal line
to anterior axillary line. This zone was splitted into an upper
region (from collar bone to the second-third intercostal
space) and a lower region (from the third intercostal space to
diaphragm). Also, the lateral area, from the anterior to the
posterior axillary line, was divided into upper and lower
halves. Finally, the posterior zone was identified from the
posterior axillary line to the paravertebral line.
The superficial layers of the thorax consist of subcuta-
neous tissue and muscles. The ribs, on longitudinal scan,
appear as curvilinear structures associated with posterior
acoustic shadowing. Pleura looks like an echogenic line,
showing a continuous intrinsic movement during breathing,
called “lung sliding sign.” The air-filled lung parenchyma
prevents any further echographic visualization under the
performed only in patients with positive US and negative CXR.
The design of the study. Computed tomography was
380S. Parlamento et al.
pleural line. However, the wide acoustic impedance
difference between pleura and the underlying parenchyma
creates typical horizontal artifacts. These are a series of
echogenic parallel lines equidistant to one another, arising
from the pleural line. These artifacts were defined “A lines”
by Lichtenstein  (Fig. 2A).
Other vertically oriented “comet-tail” artifacts (B lines
according to Lichtenstein et al  and Volpicelli et al )
might be present. B lines arise from pleural-lung interface,
reach the edge of the screen, erase A lines, move with lung
sliding, and are absent in the normal lung . These
artifacts result from the fluid-rich subpleural interlobular
septae that, in a pathologic condition defined as alveolar-
interstitial syndrome, are surrounded by air. Computed
tomographic correlations showed that B lines are related to
the presence of interstitial or interstitial-alveolar edema 
Each patient able to maintain orthostatic position under-
went posterior-anterior and lateral radiographs with a fixed
machine (Diagnostic 96; Philips Medical System, Amster-
dam, the Netherlands). If the patient, because of his clinical
conditions, could not be moved to the radiology ward, we
visualized. B lines indicate alveolar-interstitial syndrome: they arise from pleural line reaching the bottom of the screen and erasing A-line
A normal echographic lung is shown in a longitudinal view (A). Between the ribs, pleural line and multiple A lines are clearly
hyperechogenic spots (B, C). Pleural line is often hypoechogenic (B).
The echographic appearance of pneumonia. It is an irregular subpleural hypoechogenic area with air bronchograms (A, D) or many
381Evaluation of lung US for the diagnosis of pneumonia in the ED
obtained only the posterior-anterior view, using a mobile
device (Mobildrive AR15; SIAS s.p.a., Bologna, Italy).
intravenous contrast with GE Lightspeed Advantage Multi-
detector 16 CT scan (General Electric, Little Chalfont, UK).
In patients confirmed of having pneumonia, we per-
formed a follow-up after 10 days to evaluate clinical
conditions and laboratory analysis (C-reactive protein,
blood cell count), after adequate antibacterial therapy.
we collected data on body mass index, as well as associated
Outcome Research Team [PORT] index) .
The criterion to determine the echographic diagnosis of
pneumonia was the finding of subpleural lung consolidation
with evidence of static or dynamic air bronchograms (Fig. 3).
We studied 49 patients: 18 (36.7%) females and 31
(63.2%) males with a mean age of 60.9 years (SD, 21.8).
Positive CXR or CT scan and indirectly the 10 days clinical
follow-up confirmed pneumonia in 32 cases (65.3%). In this
group, we had 31 (96.9%) positive lung US and 24 (75%)
positive CXR (Table 1). Follow-up was always consistent
with the diagnosis, showing an improved clinical picture (no
fever, cough, or dyspnea) and a drop in inflammatory
laboratory indexes such as C-reactive protein.
Concordance between lung US and CXR is quite good
(k statistic = 0.63; 95% confidence interval, 0.43-0.84), but
the number of cases with positive lung US and negative CXR
is sharply superior to the number of patients with negative
US and positive CXR (McNemar P = .0196).
We could perform a complete lung US examination
(scanning anterior, lateral and posterior chest wall) in all the
patients, whereas we obtained both posterior-anterior and
lateral CXR views in 28 (66%) cases. Of the 8 patients
assessed using CT, 3 (37.5%) had also lateral CXR.
In Table 2, echographic findings are shown. Pneumonia
(Fig. 3) appears as a hypoechogenic area with irregular shape
touching the pleural line. Very often, the consolidation area is
surrounded by multiple and close B lines, that is, alveolar-
interstitial syndrome, an expression of inflammatory perile-
sionaledema. Pleural line next tothe lesionis hypoechogenic
and lung sliding is reduced or absent. Branching echogenic
structures are often visible within the consolidation repre-
senting air bronchograms and can have an intrinsic
centrifuge movement with breathing: this finding is called
dynamic air bronchogram and rules out atelectasia . Air
trapped in the small airway creates multiple millimetric
hyperechogenic spots within the lesion. These findings are
consistent with former studies in the literature and well
described also in a recent experience by Reissig and Kroegel
 (Table 2).
Toassess thefeasibility of theintegration ofthis technique
in the common ED clinical practice, we deemed it
appropriate to set a 5-minute cutoff for the execution times
of lung US. As reported in our data collection forms through
a “yes/no” question, noexamination exceeded that timelimit.
In the present study, the use of CT to clarify contrasting
results between lung US and CXR was crucial: if we had
considered CXR as the gold standard, we would have had 8
false-positive echographic results (25% of 32 confirmed
diagnoses), actually proven to be pneumonia. One of these
cases is shown in Fig. 4. This was not caused only by
patients' conditions hindering good CXR images: 3 of these
patients, as said before, had a double-view CXR. Besides, the
8 negative CXRs were evaluated by a second expert blind
radiologist. Furthermore, the percentage of false-negative
CXR of this study concerning diagnosis of pneumonia is in
line with literature data: Syriala et al , comparing high-
resolution computed tomography with CXR ability in the
diagnosis of pneumonia, found 8 (30.8%) negative CXR
cases of 26 confirmed pneumonias.
Another key point in the design of this study is that lung
US was performed before CXR by a sole expert operator:
this allows the assess of the technique itself but not the
interobserver variability in lung US image interpretation.
However, whereas the execution of US examination is
strictly dependent on the operator experience, the echo-
Results of the instrumental examinations
CT, computed tomography; CXR, chest x-ray; US, lung ultrasound.
Findings in the group examined with CT are listed in right side of the
radiologically confirmed pneumonia
Echographic findings in patients with or without
0 (0%)16 (50.0%)
382S. Parlamento et al.
graphic image interpretation itself is definitely less depen-
dent on the operator: the US pattern of a lung consolidation is
indeed completely different from an alveolar-interstitial
syndrome or a normal pattern .
Regarding echographic findings, we found 2 subpleural
consolidations in patients without pneumonia confirmation:
they were, respectively, an atelectasia caused by a large
pleural effusion and a case of pulmonary embolism . In
the first case, we excluded the infection because of the static
bronchograms course; in fact, they appeared parallel,
whereas in pneumonia they are always branching. This is
probably because the lung volume decreases in atelectasia,
whereas it increases in infectious consolidations. In the
embolism case, we observed many small bilateral subpleural
consolidations, without any bronchogram images. These
pictures, even considering the literature , suggested the
diagnosis, subsequently confirmed by contrast CT.
In essence, a subpleural consolidation in itself is not a
specific echographic sign of pneumonia, and the differential
diagnosis could be difficult.
In our survey, 5 (29.4%) patients did not have any lung
consolidation but a bilateral alveolar-interstitial syndrome: 3
of them had a diagnosis of acute pulmonary edema, and 2 of
lung fibrosis. On the other hand, in 22 (68.8%) patients with
confirmed pneumonia diagnosis, the alveolar-interstitial
syndrome was close to consolidation, as expression of a
perilesional inflammatory edema, as described before.
Fifty percent of the patients with confirmed pneumonia
presented dynamic air bronchograms: this sign, as already
shown in literature, excludes atelectasia . In addition, we
could find static air bronchograms in all patients with
We found pleural effusion in 3 patients without
pneumonia in which the final diagnosis was acute pulmonary
edema and in 11 patients with confirmed pneumonia. Pleural
effusion is frequently associated with infectious consolida-
tions, but also with many other diseases, as it is well known.
As said before, a lung consolidation becomes evident to
US examination only if it reaches pleural surface. In the
present study, all the consolidations interpreted as pneumo-
nia satisfied this condition. In fact, even in the only case
where we had with positive CXR and negative lung US, we
could visualize the consolidation performing lung US once
CXR response was acquired. We could not find in literature
anatomopathologic data regarding the percentage of CAP
reaching pleural surface, but from some previous experi-
ences [9,27], it appears to be definitely elevated.
In this study, we did not describe localization, shape,
and dimensions of pulmonary consolidations because this
kind of assessment is far from the “goal-directed” approach
of emergency US.
As stated above, we could obtain a complete lung US
examination in all patients, aside from their body mass index,
associated clinical conditions, and pneumonia severity: this
showed no sign of pneumonia (A and B), whereas CT scan (C) confirmed the right basal consolidation shown by lung US (D).
A 22-year-old patient presenting with pleural pain and cough. Results of instrumental examinations are shown: double-view CXR
383Evaluation of lung US for the diagnosis of pneumonia in the ED
demonstrates the high versatility of this technique. Further-
more, the execution rapidity, even if obtained by an expert
operator, shows that bedside lung US does not interfere with
common ED diagnostic workup of pneumonia.
The main limitation of this study is the small number of
patients enrolled; however, statistical analysis shows sig-
nificant results, especially concerning the asymmetry of
McNemar test, favorable to lung US.
It is not possible to infer conclusive data on sensitivity and
specificity of bedside lung US in the diagnosis of pneumonia
from this study as, because of ethical reasons, we did not
perform CT (considered as the gold standard) in all patients.
Nevertheless, regarding sensitivity, it is encouraging that
we had an alternative diagnosis (with consequent therapy)
for each patient without confirmed pneumonia. Concerning
specificity, beyond the CT results, follow-up results were an
indirect evidence of the diagnosis correctness.
Finally, it is important to say that the lung US operator
was not blind concerning clinical presentation of patients.
Considering the limitations of the present study, further
close examinations are needed to assess the sensitivity and
specificity ofbedsidelungUSin thediagnosis ofpneumonia.
We clearly confirmed the feasibility of lung US in an ED
setting, already reported in the literature .
technique, these results suggest it could have a significant
role in the diagnostic workup of pneumonia in the ED.
In particular, if the accuracy of lung US is confirmed,
execution rapidity of this examination will appear very
relevant for the emergency and critical care area, especially if
it is compared to the time required to obtain the results of
Noninvasivity is also a striking quality of this technique,
especially concerning its use in children, pregnant women,
and, as recently shown in literature , even for the follow-
up of lung lesions.
In conclusion, we believe that lung US in emergency
physician hands, for the first approach to patients with
pneumonia suspicion, could be an interesting tool for these
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