Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_857_Библиотеки_им_академика_М_И_Перельмана
.pdf
REFLECTOR
20 How toUse Surgical Ultrasound inResource-Limited Settings
https://t.me/medicina_free
TRANSDUCER
emitted
absorbed
Fig. 20.2 Wave behavior in a medium
reflected
scattered
205
refracted
transmitted
ated by a transducer that has the ability to transform electrical energy into mechanical energy
(known as the piezoelectric effect). It is this
acoustic energy that is transmitted through the
medium. As the wave travels, it may encounter
architecture in the medium that will change its
direction. If the direction of change is at a forward angle, it is refracted; if the wave changes
directed back toward the source (transducer), it is
reected. Scattering refers to a type of reection
and refraction due to very small details in the
medium, on the order of the wavelength of the
acoustic wave. The acoustic energy may also be
“lost” in the medium through transformation to
thermal energy (absorption), which relates to
inherent properties of the medium. All of these
behaviors are sensed back at the receiving aspect
of the transducer, where the acoustic energy is
transformed back to electrical energy, which is
then used to compute the nal image.
Each of these processes is inuenced by the
frequency of the incident wave. As a rule, the
higher the incident frequency, the greater the
energy “loss” or attenuation. The attenuation
coefcient is a unique property of media, and for
soft tissue, it may be approximated as 0.5dB/cm/
MHz. In the application of medical ultrasound,
this inuences your choice of transducer frequency; although a higher frequency of sound
would result in clearer images (higher resolution), this is limited by the attenuation of the
sound wave. In other words, you would use a
lower-frequency transducer to reach deeper
structures (at the sacrice of image clarity), since
the greater distance a wave must travel means it is
attenuated more. Conversely, one would choose a
higher-frequency transducer for more supercial
structures (to optimize detail).
There are several different image options on
commercial ultrasound equipment. Perhaps the
most familiar is the B-mode or two-dimensional
grayscale image. Depending on transducer construction, this may appear as a rectangular image
or a wedge-shaped “sector” scan. Doppler ultrasound, which allows for ow velocity measurements based on the Doppler effect, may be
superimposed on the B mode image for a duplex
scan. In this mode, a cursor is directed to the
point of interest (e.g., blood vessel) to assess for
movement, which is displayed as color superimposed on the grayscale image. Arbitrarily, a red
color may signify movement away from the
transducer, and blue indicates ow toward the
transducer. Most relevant here of course is direction of movement with different structures in the
image relative to each other. Flow velocity may
be quantied and displayed as well; triplex ultrasound is a term sometimes used to indicate
B-mode image, color ow map, and velocity
quantication on one image. Commonly used to
assess heart valve motion in echocardiography,
M-mode tracks velocity variation over time.
Scanning Techniques
Medical ultrasonography is a unique imaging
modality in that the user’s manipulation of the
206
https://t.me/medicina_free
B. A. Schrope et al.
transducer or indeed the patient aids in image
interpretation; thus, it is a dynamic and interactive skill. Practically, there are several key tips to
successful ultrasound image interpretation.
Starting with transducer selection, considerations
include transducer footprint and frequency. Small
anatomic regions such as the neck are best served
with smaller-sized probes. Higher-frequency
transducers deliver better image clarity, but attenuation of the acoustic energy limits frequency
capability in imaging deep structures. Thus, thyroid or supercial vascular structures, for example, are well served by higher frequencies (7.5 to
10 MHz), but transabdominal imaging may
require a 5 MHz probe. Many commercially
available probes offer multifrequency probes,
where a single probe can deliver a range of frequencies depending on user selection. Note that
transducer orientation may be veried before
every examination by touching one side of the
probe and observing the corresponding area on
the image where the signal is noted. Of course,
coupling gel is mandatory with transcutaneous
scanning; dedicated sonography gels can be used,
but medical lubricants are also quite ne.
The image may be optimized with various
front panel controls. In general, the desired anatomy should ll the image; thus, the user should
adjust the depth to include the region of interest
and nothing beyond. This of course magnies
the image but also mitigates any artifact from
structures beyond the region of interest. In terms
of “brightening” the image, two aspects of the
signal may be manipulated. First, the power to
the transmitted signal may be increased. This
results in a stronger incident acoustic pulse,
which may aid in targeting deeper structures.
This can result in unacceptable “noise” or distortion of parts of the image, however. An alternative is to increase the amplication or gain of the
received signal. Here one can select to amplify
the signal from different depths of the image;
this is typically referred to as Time Gain
Compensation (TGC) and seeks to account for
cumulative attenuation of the signal as it travels
over a longer distance. Many commercial
machines have a series of slide switches to
change the gain at various depths in the image.
Finally, dynamic range refers to the range of
echo amplitudes processed and displayed by the
system, from strongest to weakest, analogous to
the concept of contrast in video applications.
The strongest echoes received are those from the
initial impulse and transducer- skin interface and
will generally be similar from exam to exam. As
the dynamic range is decreased, the echoes at the
weaker end of the spectrum will be lost. For
most imaging applications, the dynamic range
should be kept at its maximum level to maximize
the contrast of the image.
Image interpretation may be facilitated with
the appreciation of a few simple principles, based
on the physics lesson provided previously.
Imaging artifacts are phenomena occurring as a
result of ultrasound’s interaction with the
medium. Although artifacts can be considered
“false” impressions, recognition and characterization of artifacts are vital to optimal image
interpretation. It is also important to recognize
the fact that ultrasound is a dynamic procedure,
so artifacts can often be distinguished from genuine by scanning in different planes or by adjusting the system controls.
Acoustic properties of different soft tissues
vary slightly, which aids in differentiation of
structures (muscle, fat, solid organ, tumor, etc.).
In addition, water is very different from soft tissue; thus, cystic structures are readily apparent
and discernable from surrounding soft tissues.
Specically, the acoustic signal is minimally
attenuated through water, so an artifact known as
posterior enhancement can be diagnostic in evaluating cystic structures. Further, waves can
“bounce” within the connes of a cyst creating
articial structures within the cyst on this image,
which is known as reverberation artifact. Needles
used for biopsy or aspiration display a particular
type of reverberation artifact due to the large
acoustic impedance mismatch between metal and
water, known as a comet tail artifact.
Another type of reverberation artifact, referred
to as ring-down artifact, occurs when there are
small bubbles of air or partial liquids in the insonied eld. A classic example is adenomyomatosis of the gallbladder, where acoustic energy
reverberates between and within the bile-lled
20 How toUse Surgical Ultrasound inResource-Limited Settings
https://t.me/medicina_free
207
cystic spaces of the hyperplastic gallbladder
epithelium.
Calcied structures such as bone or calcied
stones, as well as air, also have different acoustic
properties from soft tissues. For example, calcied gallstones will reect acoustic energy much
more strongly that surrounding soft tissues, leading to a shadowing artifact behind the stones. Air
in the trachea will also strongly reect acoustic
energy, demonstrating an important landmark in
neck imaging.
Training andCertication
Currently, many surgical residencies incorporate
ultrasound training into their programs, thus
enabling a graduating surgeon to incorporate
ultrasound into their chosen practice fairly easily.
And, as with any surgical skill, competence is
gained through experience. Realistically, though,
there are circumstances where a surgeon may not
have had the opportunity to gain adequate training during residency, either due to decit in the
program or maturity in their careers. In this case,
the acquisition of new skills should follow a standard rubric, namely, (1) didactic instruction by
experts in the eld; (2) hands-on training; (3)
proctoring for an agreed amount of cases with
eventual demonstration of satisfactory skill; and
(4) continuing education, both practical (e.g.,
meeting a minimum number of cases per year)
and quality assurance.
There are numerous excellent options for
didactic online instruction in surgical ultrasound.
The American College of Surgeons, for example,
has published a comprehensive course,
UltraSound Essentials for Surgeons (USES),
available online for a nominal fee. The World
Federation for Ultrasound in Medicine and
Biology is another resource rich with online videos and courses, depending on an individual’s
particular interest. Indeed, hands-on training in
ultrasound, as with any new skill, is best learned
with a knowledgeable proctor. Fortunately, as
ultrasound is a completely noninvasive entity
with no known adverse bioeffects, a user can
“practice” with known anatomy or pathology
until they are comfortable with their skills, should
a live proctor be unavailable. This may be the
only option to gain competency in certain
resource-limited areas of the world. In the case of
surgeon-performed ultrasound, as with any surgical practice or skill, at minimum, periodic selfassessment of quality should be assured.
Neck Ultrasound
Ultrasound is an accessible and noninvasive diagnostic tool that often serves as the imaging of
choice in the workup, diagnosis, and treatment of
various thyroid, parathyroid, and lymphatic
pathology. Advances in high-resolution imaging
and the improved versatility of ultrasound have
led to an exponential increase in point-of-care
ultrasound exams [1]. For example, trained individuals can not only rapidly determine whether
further workup is warranted, but they can also
use the dynamic feedback to assist with procedures including biopsies of the thyroid or lymph
nodes, cyst drainage, transcutaneous laryngeal
ultrasonography of the vocal folds, and
ultrasound- guided ethanol or radiofrequency
ablation of thyroid nodules. Furthermore, surgeons often use ultrasound intraoperatively to
evaluate for any progression of disease since consultation and to plan the ideal placement for the
cervical incision. The focus of this section will be
on the use of ultrasound to evaluate the thyroid,
the parathyroid glands, and the cervical lymph
nodes.
Thyroid
Sonographic evaluation is one of the initial steps
in the workup of thyroid disease. A dedicated
thyroid ultrasound consists of several components: a description of the thyroid parenchyma
(heterogeneity, vascularity), the size of each
thyroid lobe (length, width, and height), a
description of any thyroid nodules, and an evaluation of the cervical lymph nodes (both central
and lateral) [2]. A thorough evaluation of those
features can aid in the diagnosis of thyroid nod-
208
https://t.me/medicina_free
B. A. Schrope et al.
ules, thyroiditis, multinodular goiter, Graves’
disease, and malignancy. When evaluating thyroid nodules, there are several important characteristics to note including location, size,
echogenicity, composition (solid vs. cystic),
vascularity, presence of calcications, and borders [2, 3]. While certain ultrasound characteristics correlate with a higher risk of malignancy
(microcalcications, taller than wide shape, and
irregular borders), the sensitivity of any individual characteristic is less than 70% [3–5].
Consequently, there are two validated ultrasound classication systems that are commonly
used to assess and report sonographic features
of thyroid nodules and to stratify the risk of
malignancy of the nodule.
The American Thyroid Association (ATA)
ultrasound classication straties thyroid nodules into ve different groups: benign, very low
suspicion, low suspicion, intermediate suspicion, and high suspicion (Fig.20.3). Each category correlates to a different risk of malignancy
that guides the clinician on whether a ne-needle
aspiration (FNA) biopsy is warranted [6–8]. The
American College of Radiology developed the
Thyroid Imaging Reporting Data System
(TI-RADS) in 2012 that utilizes a points-based
system to assign nodules to ve different categories: benign, minimally suspicious, moderately
suspicious, or highly suspicious for malignancy
(Fig.20.4) [2, 9, 10]. While both the ATA and the
TI-RADs classication systems have high sensitivity (92% and 74%, respectively), the ATA
classication was found to demonstrate more
consistent predictions for risk of malignancy
among higher-risk nodules [11].
In general, the level of sonographic suspicion
will guide the recommendation for a FNA biopsy.
However, it is also important to take into account
patient risk. For example, if a patient has known
risk factors associated with thyroid cancer including exposure to radiation, a family history signicant for thyroid cancer, new onset of symptoms
(changes in voice), and a rapidly growing nodule,
Fig. 20.3 American Thyroid Associate (ATA) ultrasound characteristics and risk of malignancy [2]
20 How toUse Surgical Ultrasound inResource-Limited Settings
https://t.me/medicina_free
209
Fig. 20.4 American College of Radiology (ACR) Thyroid Imaging, Reporting and Data System (TI-RADS) [9]
an FNA should be considered at a lower size cutoff in all categories [12].
While the low cost and easy access of ultrasound are largely benecial in the workup of thyroid nodules, especially in a resource-limited
setting, these benets of ultrasonography can
result in an increase in incidental ndings that
contribute to the burden of overdiagnosis in our
healthcare system [9, 13, 14]. Thus, it is imperative to use ultrasound in the neck selectively to
help guide the workup and not simply as a routine extension of the physical exam.
neous and have an extrathyroidal feeding vessel
[15]. Although ultrasound is limited in the ability
to provide functional information (as with a
99mTc-sestamibi scintigraphy) or anatomic
detail for posterior and mediastinal glands (as
with a 4DCT scan), one study found that it was
the most cost-effective localization strategy [16].
Furthermore, another publication demonstrated
that a surgeon performed preoperative ultrasound
in a patient with primary hyperparathyroidism
had a sensitivity of 76% and specicity of 97% to
accurately localize a diseased parathyroid
gland(s) [17].
Parathyroid
Cervical Lymph Nodes
Ultrasound is often utilized for localization of
enlarged parathyroid glands in the setting of
hyperparathyroidism. Diseased parathyroid
glands typically appear hypoechoic and homoge-
When evaluating a patient with neck pathology, it
is important to perform a complete assessment of
the cervical neck lymph nodes. Adults typically
210
https://t.me/medicina_free
B. A. Schrope et al.
have hundreds of lymph nodes in the cervical
neck, and fortunately, benign lymph nodes have
several classic characteristics: small ovoid/at
shape, clear borders, homogeneous appearance,
or echogenic hilum with vascularity (or a
preserved “fatty hilum”). On the other hand, suspicious characteristics include a rounded appearance (or a long/short axis ratio < 2), loss of
echogenic hilus (loss of fatty hilum), cystic
change, ill-dened borders, peripheral vascularity, or calcications [18]. One study indicated
that the loss of a fatty hilum was the most sensitive nding for malignancy at 100%, but with a
limited specicity of only 29% [19, 20]. The
most specic characteristics for malignancy
include cystic degeneration (100%), microcalcications (100%), and hyperechogenicity (100%)
[21]. However, as with thyroid nodules, no single
characteristic is predictive of malignancy, and
thus the absence of benign features and/or the
presence of any suspicious characteristics warrants an FNA biopsy if the nodule measures
greater than 8mm [22].
Furthermore, the location of suspicious lymph
nodes in the neck can be suggestive of different
pathology. For example, thyroid cancer typically
metastasizes to levels II–VI.However, lymphadenopathy in the posterior triangle increases the suspicion for nasopharyngeal carcinoma. If a lymph
node is noted in the inferior portion of the deep
cervical chain (known as “Virchow’s node”) with
an absence of any lymphadenopathy caudal to
that point, this is concerning for a metastasis [18].
Utilization andTraining
The National Ultrasound Faculty of the American
College of Surgeons offers several ultrasound
courses at the annual Clinical Congress for students, residents, and faculty. Courses include an
introductory ultrasound course for residents, a
focused echocardiography/ICU ultrasound
course, and a thyroid, parathyroid, and neck
ultrasound course. Participants are required to
complete an online course and subsequently gain
hands-on experience during the practical session.
Fortunately, more institutional-based programs
are also being developed in response to the
increasing need for clinicians to be procient at
performing diagnostic ultrasound [23, 24]. Still,
the accessibility to a training course to learn
ultrasound can be a barrier for clinicians in a
resource-limited setting. Furthermore, according
to the American Institute of Ultrasound in
Medicine (AIUM), clinicians need to perform a
minimum of 100 diagnostic thyroid, parathyroid,
and neck ultrasound examinations to gain prociency. Additionally, in order to obtain ofcial
credentialing, applicants need to document 15
CME credits dedicated to thyroid, parathyroid,
and neck ultrasound [25].
Summary
Ultrasound is often the imaging modality of
choice in the workup and diagnosis of thyroid,
parathyroid, and cervical lymph node disease.
The relative low cost and accessibility of ultrasound make it an ideal tool to use, especially in a
resource-limited setting. With the ongoing development of ultrasound training programs, healthcare providers can reach prociency and more
effectively utilize this technology in low- to
middle- income countries.
Breast Ultrasound
An ultrasound machine and skill set are versatile
tools in diagnosing and managing breast symptoms in low-resource settings. It can eliminate an
unnecessary visit to the operating room for excisional biopsies as well as guide further treatments
and interventions. Having a correct linear probe
with center frequency at 12MHz and knowing
how to adjust depth, gain, and focal zone are
critical for the diagnosis and management of
many breast problems.
Breast Screening
The incidence of breast cancer continues to
increase worldwide [26], which is currently the
20 How toUse Surgical Ultrasound inResource-Limited Settings
https://t.me/medicina_free
leading cause of cancer-related deaths in females
[27]. Screening for breast cancer allows for early
detection and improved survival [28]. In Western
countries, mammographic screening programs are
widely utilized and readily available [27].
Mammography, however, requires specialized
infrastructure that includes equipment, personnel,
and trained radiologists. In low-resource settings,
the infrastructure and expertise requirements may
not be feasible on the large scale required to
achieve oncologic benet. Additionally, a trend
toward younger age at diagnosis and subsequent
denser breast tissue [29] may diminish the sensitivity of mammography [30] in many non-Euro-
Fig. 20.5 Cyst with anechoic interior with regular borders, wider than tall appearance
pean populations. Ultrasound screening has been
explored as an alternative to mammography.
Advantages include its portability, lower cost, and
potential to utilize trained community health
workers for initial assessment rather than radiologists [27]. It can be a part of widespread asymptomatic screening [31] or utilized as part of specic
programs that target high-risk or symptomatic
populations [32]. A meta-analysis by Sood etal.
[27] demonstrates an overall acceptable pooled
sensitivity of 80.1% and a specicity of 88.4%.
211
Palpable Mass
Focused ultrasound can be used for palpable
breast masses to differentiate between cystic and
solid lesions. Completely anechoic, collapsible,
round lesions (Fig.20.5) in an otherwise low-risk
patient is a simple cyst that can be observed or, if
symptomatic, can be aspirated by giving a small
amount of 1% lidocaine and aspirating with a
22G needle until the cyst collapses. When clear,
straw or green-colored uid is obtained, it can be
discarded as concordant and benign. The patient
is usually counseled that there is a possibility of
cyst recurrence in these situations. However, they
are reassured by the benign nature of the palpable
mass, and in symptomatic patients, immediate
relief is usually observed. Bloody uid aspirate
should be sent to cytology for testing by preparing slides or rinsed in a container with CytoLyt®
or formalin uid. A clip or marker can be placed
at the site of a bloody cyst to mark the area for
Fig. 20.6 Fibroadenoma with macrolobulations around
the border and hypoechoic lesion of the breast
future surgeries if needed. These cysts may need
excisional biopsies to get a full diagnosis or at
least observed with repeat ultrasound in 3 to
6months.
For solid lesions seen as hypoechoic, other
characteristics such as borders of the lesion and
shadowing, together with patient risk assessment,
help determine whether a lesion should be biopsied [33]. In an otherwise, young patient with a
lack of family history of breast cancer, a wider
than tall, hypoechoic lesion with regular borders
is usually broadenomas (Fig.20.6) and can be
safely observed. For lesions with irregular borders, shadowing, or rapid growth or patients with
a signicant family history of breast cancer,
ultrasound-assisted core biopsy can be performed. Once the pathology concordance is
212
https://t.me/medicina_free
achieved, no further observation is needed for
broadenomas. Discordant lesions should proceed with excisional biopsies or observed with
repeat scans in 3 and 6months.
Nipple Discharge
Another use of breast ultrasound is to evaluate
patients with nipple discharge. In patients who
present with pathologic nipple discharge, ultrasound of the retroareolar region may identify
papillomas or a malignant lesion as the source of
the discharge. Ultrasound-guided biopsies of
these lesion can help diagnose a patient and prepare the patient for denitive surgery.
Inammatory Disease
The most common use of ultrasound in breast
care is to evaluate inammatory diseases such as
an abscess and cellulitis in the context of clinical
presentations. Abscesses appear as a hypoechoic
collection without vascularity with a thickened
rim and increased echogenicity of breast parenchyma reecting edema and inammation [34].
Aspiration of the abscess with an 18G needle
after local anesthesia under ultrasound is recommended for most deep abscesses [35]. In the situation where inammatory breast cancer is
considered, biopsy of the tissue or skin punch
biopsy should be obtained.
B. A. Schrope et al.
Fig. 20.7 Normal-appearing lymph node with intact
hilum and thin cortex
rather than upfront surgery to downstage the disease in axilla. This can avoid challenging surgical
situations in the operating room, perhaps avoid
complete axillary dissection if there is no residual disease after neoadjuvant treatment, and
decrease the risk of lymphedema for the patient.
In addition to the axilla, ultrasound can also evaluate palpable cervical and supraclavicular nodes
and biopsy as needed based on clinical exam.
Within a similar anatomic region, ultrasound
can be utilized in breast care by providing
regional blocks for surgeries such as pectoral I
and II blocks in the perioperative setting for pain
control [37].
Breast Ultrasound Certication
Axillary Ultrasound
Particularly important in patients who are already
diagnosed with malignancy is an axillary ultrasound during preoperative workup where up to
50% of positive metastatic node involvement can
be detected [36]. For patients with a palpable
axillary node, ultrasound can aid with biopsy to
avoid injury to vascular structures. Findings of an
irregular node with a thickened cortex should be
biopsied to further stage the patient (Fig.20.7). If
the node has metastatic disease, patients may be
a better candidate for neoadjuvant treatment
In the United States, the American Society of
Breast Surgeons offers training courses and certication to surgeons, which are also accepted by the
American College of Radiology. A minimum of
1-year experience with documented performance
of at least 100 breast ultrasound exams among others is required before taking a written exam and
submitting cases for the certication process.
Thoracic Ultrasound
An obvious application of ultrasound in the thoracic cavity is of course echocardiography, a
20 How toUse Surgical Ultrasound inResource-Limited Settings
https://t.me/medicina_free
213
complex and unique practice. With the exception
of assessment for pericardial effusion, the heart is
not commonly under the purview of the general
surgeon. Yet this region of the body also houses
organs that can fall under the practice of the general surgeon (and surgical intensivist). In particular, diagnosis and treatment of pneumothorax,
hemothorax, pleural effusion, and even pulmonary contusions and rib fractures are all facilitated with ultrasound.
As the ribs are acoustic barriers, one must
choose a small footprint transducer to image
between the ribs to see into the thoracic cavity.
Air also has a signicant acoustic impedance
mismatch from soft tissues, but this can be a
diagnostic advantage.
Ultrasound can often be utilized quicker than
conventional X-ray to detect a pneumothorax.
Indeed, in experienced hands, ultrasound should
be able to detect 90–100% of pneumothoraces
[38]. Ideally, the patient should be sitting up
about 30 degrees. The examiner starts with the
lung apices, in the second rib interspace, because
in the upright position this is most likely where
air will accumulate. Start from the probe-skin
interface, the rst structure noted in the chest
wall musculature. Distal to that is the pleura. The
parietal and visceral pleura normally slide against
each other, lubricated by a small amount of uid.
This sliding motion can be visualized with ultrasound and is often described as “ants marching”
along the pleural interface (Fig. 20.8a). The
dynamic advantage of ultrasound makes this
even more apparent during the real-time ultrasound exam. If the image depth is too large, artefactual “A-lines” will be seen, which are
reverberation echoes of the pleural line. In the
case of a pneumothorax, air between the pleural
surfaces prohibits this sliding motion, where the
absence of motion can be detected with cine
ultrasound. It is important to be aware that pleural sliding may also be absent in patients with
lung damage from COPD or pleurisy, even if no
pneumothorax is present. Finally, multiple interspaces must be evaluated to increase the accuracy
of diagnosing NO pneumothorax.
a
b
c
Fig. 20.8 (a) B-mode image of chest. The rst layers
seen are the musculocutaneous layers of the chest wall,
followed by a hyperechoic pleural line. In the real-time
view, the pleural sliding movement is more apparent and
likened to “ants marching.” (b) M-mode image of normal
lung, where the chest wall (at the top of the M-mode)
appears as waves, and the pleurae appear as grains of
sand, due to the slight motion of normal pleural sliding.
(c) M-mode image of a pneumothorax, where the grainy
appearance of normal sliding pleurae is lost and replaced
by a more dened appearance of lines or bars (“bar code
sign”) [39]
214
https://t.me/medicina_free
B. A. Schrope et al.
ab
Fig. 20.9 (a) Probe position to obtain B-mode image at
right. (b) Two-dimensional B-mode image of patient with
pleural effusion. The hyperechoic structure is a partially
Further evaluation for pneumothorax can be
quickly assessed by switching to M mode, which
will characterize the motion of the lung with
respect to the chest wall. In M mode, starting at
the surface of the transducer, the pattern of the
stationary chest wall looks like ocean waves.
Deep to that, the motion of pleural sliding produces a grainy pattern similar to the appearance
of sand on a beach (Fig.20.8b). These ndings
are often described as the “seashore sign.” In the
case of a pneumothorax, the pleura is not moving, and the grains of sand are not present.
Instead, a continued series of horizontal lines
continues deep to the chest wall (the “stratosphere sign”) (Fig.20.8c). This is also referred to
a “bar code pattern.”
To assess for a pleural effusion, if at all possible (i.e., no spinal injury or mechanical ventilation), it is best to have the patient sit up to allow
for uid to accumulate at the lung bases.
Alternatively, placement of the patient in the lateral decubitus position is preferable to a supine
position. The ultrasound probe should be placed
below the 11th rib in the midaxillary line for
assessment of an effusion. The diaphragm should
be apparent as a bright white line, and uid if
present can be seen as hypoechoic density above
the diaphragm (Fig.20.9). The lung may also be
more hyperechoic than normal if it is collapsed.
If uid is visualized, a needle, wire, and/or catheter can all be placed under direct ultrasound
visualization for drainage.
collapsed lung. The yellow dotted line is spanning one
axis of the uid volume [40]
Ultrasound intheEmergent Setting
Its portability and ease of use make ultrasound an
invaluable tool in the assessment for surgical
emergencies. In this section, we will discuss
more common scenarios including FAST exam,
acute cholecystitis, acute appendicitis, and
assessment for abdominal aortic aneurysm. In
addition, tips for ultrasound-guided procedures
such as percutaneous drainage of abscesses, ascites, or placement of cholecystostomy tube are
reviewed.
Trauma
Blunt or penetrating trauma with potential for
thoracoabdominal injury presents a scenario
where speed of diagnosis and treatment is of the
essence. Central to the sonographic evaluation
for trauma is the FAST exam, or Focused
Assessment with Sonography for Trauma. This is
a simple-to-perform tool that will evaluate for
free uid in the anatomic spaces of the abdomen
as well as the pericardial space. Unlike CT scan,
this can be performed at the bedside or even in
the eld. Unlike diagnostic peritoneal lavage,
ultrasound is noninvasive and of similar accuracy
(and arguably a more thorough assessment as the
pericardial space is also evaluated).
The FAST exam consists of four components
or views (Fig.20.10). These need not be com-
Соседние файлы в папке Библиотека им академика М.И. Перельмана