Pediatric emergency medicine trisk 1131
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FIGURE 131.27 Hyperechoic spinous processes.
In most cases, the static technique is used to identify anatomical landmarks
before the procedure. It is feasible to use ultrasound in real time; however, there
are challenges to the dynamic technique. First, the procedure requires a sterile
sheath and sterile gel. Second, it may require a second person to hold the probe
while the clinician performing the lumbar puncture inserts the needle. In the
dynamic technique, the probe is placed in the longitudinal axis and the needle
inserted below the probe (Fig. 131.30 ). This technique may be cumbersome for
the novice sonographer.
Pitfalls
The major pitfall with imaging the spine is being off axis. Like the spinous
process, the transverse process will also appear hyperechoic and may confuse the
sonographer. To avoid confusion, clinicians should scan side to side, and up and
down, and ensure that the bony landmarks identified as the spinous processes are
the most superficial. Then the transverse view of the spine can confirm the image
is midline and not off axis.
FIGURE 131.28 Neonatal spinal canal in long axis.
FIGURE 131.29 Neonatal spinal canal short axis.
SOFT TISSUE ULTRASOUND
Soft Tissue Infections
POCUS is useful for differentiating cutaneous abscesses from cellulitis in
children presenting to the ED with soft tissue infections. Ultrasound can also be
used to identify the most fruitful site for incision into an abscess and to identify
critical structures to avoid during incision (e.g., blood vessels and nerves),
thereby minimizing procedural complications.
FIGURE 131.30 Photograph displaying dynamic technique for lumbar puncture.
FIGURE 131.31 Normal soft tissue.
Technique
Most soft tissue structures are superficial and are best interrogated using a highfrequency linear transducer. Scanning should extend from nearby uninvolved
structures through the entire region of the affected area. Images should be
obtained in both the longitudinal and transverse planes. Normal dermis and
epidermis appear hyperechoic in relation to the deep subcutaneous fat globules
(Fig. 131.31 ). Fascia appears as a linear hyperechoic layer and muscle can be
identified as hypoechoic cylindrical structures surrounded by hyperechoic
perimysium (Fig. 131.32 ). Interstitial edema in cellulitis is apparent as
hypoechoic fluid separating the hyperechoic fat globules. This effect is known as
“cobblestoning” (Fig. 131.33 ). Abscesses have a variable appearance, but most
often are identified as anechoic or hypoechoic collections of fluid (Fig. 131.34 ).
Gentle compression of the abscess with the US probe can elicit fluid movement
confirming the presence of a fluid collection ( Video 131.30 ).
Pitfalls
Cysts appear as anechoic structures with posterior enhancement and can be
mistaken for abscesses. However, they often have a more regular oval shape and
do not exhibit surrounding interstitial edema as seen in cellulitis. Normal or
