Diagnostic ultrasound ( PDFDrive )

1702 PART V Pediatric Sonography
Indications for Extracardiac
Chest Sonography
FLUID ACCUMULATION IN THE PLEURA
Pleural effusion
Empyema
LUNG DISORDERS
Pneumonia
Atelectasis
Sequestration
Congenital pulmonary airway malformation
Bronchopulmonary foregut malformation
DIAPHRAGM DISORDERS
Diaphragmatic paralysis
Diaphragmatic hernia or defect
Diaphragmatic rupture
VASCULAR DISORDERS
Vascular thrombosis
Vascular malformation
MASSES
Mediastinal, chest wall, and at times pulmonary masses
INTERVENTIONAL INDICATIONS
Thoracentesis
Biopsy of chest mass
Sclerotherapy of lymphatic malformation
Vascular access
OTHER INDICATIONS
Catheter position in vessels
Pneumothorax
Rib fracture
Rib osteomyelitis
Bronchiolitis
Sector or vector transducers are used for intercostal and
suprasternal approaches. Linear transducers with the long axis
of the transducer aligned with the intercostal space can also be
used. We have found that the smaller footprint of newer linear
transducers provides improved resolution compared with vector
transducers using the intercostal window (Fig. 50.1). Newer
technology has allowed for increased portability of ultrasound
equipment such that some ultrasound probes can connect directly
to a tablet or smart phone device. he resolution of these newer
devices is currently a limiting factor.
In children younger than 1 year, sternal ossiication centers
are unfused, the mineral content of the bones and cartilage is
lower than in older children, and the thymus is much larger
relative to other structures. Acoustic windows through the
sternum, costal cartilages, and thymus allow ultrasound evaluation
of mediastinal structures. In older children transabdominal
ultrasound of the lower chest, including the diaphragm, can be
performed using the liver, spleen, or luid-illed stomach as an
acoustic window. Sector, vector, or linear array transducers can
be used for this purpose.
Free pleural luid is dependent in position and will shit
with patient positioning. Ultrasound of the dependent
areas will identify free pleural luid. Loculated luid will
necessarily be in a dependent position but may move with
positioning.
hree longitudinal planes are used for assessment of the
mediastinum (Fig. 50.2): right parasagittal plane through the
superior vena cava (SVC), sagittal plane through the aortic root,
and let parasagittal plane through the pulmonary outlow tract.
Two distinct transverse planes through the mediastinum are
also routinely used (Fig. 50.3): the superior plane at the conluence
of the brachiocephalic veins and SVC and a lower transverse
plane where the SVC, aorta, and pulmonary outlow tract are
visualized.
PLEURAL EFFUSION AND EMPYEMA
he most frequent use of chest sonography is for the evaluation
of a completely radiopaque hemithorax (Fig. 50.4) or
a partially radiopaque hemithorax (Fig. 50.5). Ultrasound
distinguishes pleural from pulmonary causes of opaciication.
Chest ultrasound is more sensitive than decubitus radiographs
for detecting small amounts of pleural luid (Fig. 50.6). Pleural
luid collections less than 4 mm in thickness can be physiologic
and detected in normal children placed on their elbow ater
lying for 5 minutes in a let lateral decubitus position. 3 Because
pleural efusions transmit sound waves, they allow for visualization
of structures deep to the pleura that are not normally
identiiable.
Intercostal and subdiaphragmatic windows are used to access
the pleural space. he spleen and liver are good windows to the
pleural space because they are relatively homogeneous solid
organs that provide good through transmission (Figs. 50.7 and
50.8). he classic appearance of transudative pleural efusion is
an echo-free or hypoechoic collection without septations immediately
deep to the chest wall. However, it should be recognized
that exudates can also be anechoic and that transudative pleural
efusions are anechoic and nonseptated in only 45% of patients. 4
herefore echogenicity in pleural collections does not exclude
the diagnosis of a transudate.
Exudates are usually complex collections with internal
echoes and associated ibrin septations. he collections may be
multiloculated with a honeycomb appearance. 5 Exudates are
associated with pleural thickening and underlying parenchymal
abnormality. 6 Complex collections such as a hemothorax
(Fig. 50.9) or empyema (Fig. 50.10) have thicker luid with
septations (Fig. 50.11). Underlying consolidated or atelectatic
lung is more echogenic than an efusion. Complicated efusions
are characterized by an irregular or indistinct interface
between pleura and the adjacent lung. A ibrothorax has a
thick pleural rind that is echogenic. Multiple hyperechoic
foci in the lung are caused by residual air within bronchi
and alveoli and are called sonographic air bronchograms
(Fig. 50.12).
Text continued on p. 1709.