SMALL PARTS PROBE

Find the Bullet Challenge

(answer down 10 images)

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Small Parts Pearls & Pitfalls:

ABSCESS VS. CELLULITIS by Teresa Wu, MD

• Ultrasound can be used to help you delineate whether the patient has cellulitis versus an occult abscess present. Scanning the area of interest will identify the size and depth of the fluid collection requiring incision and drainage.
• Soft tissue applications should be performed with a 5 to 7.5 MHz linear array transducer.
• Apply a large amount of ultrasound gel to improve your acoustic interface. If the patient is thin and devoid of much subcutaneous fat, you may need to utilize an acoustic standoff pad to improve your sonographic window.
• Start by scanning normal tissue margins surrounding the area of interest. Note that normal subcutaneous tissue will have dark, hypoechoic regions of fat mixed in with brightly hyperechoic muscle, facial, and tendon planes.
• As you scan towards the area of interest, look for a spherical or elliptical collection of hypoechoic material indicating abscess formation. The hypoechoic or anechoic fluid collection may have ring enhancement indicated by a rim of hyperechoic surrounding tissue.
• Abscesses may appear hypoechoic or anechoic during the initial stages of formation. As the inflammatory process progresses, the pus may begin to appear more heterogeneous with a mix of hypoechoic and hyperechoic material swirled together.
• Always obtain images in multiple planes (longitudinal, transverse, oblique) to help define the borders.
• Identify surrounding nerves, lymphatic channels, and vessels to help prevent accidental puncture during an I&D.
• Remember that pseudoaneurysms and large vessels may look like a fluid filled abscess on ultrasound. If you image in multiple planes, a vessel will appear as a cylinder but an abscess will remain egg-shaped. When in doubt, apply Color-Doppler to the area of concern.
• Utilize contra-lateral limbs and adjacent areas of normal appearing tissue for comparison

Cellulitis by soft tissue ultrasound.  Courtesy of Teresa Wu, MD

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Abscess by soft tissue ultrasound.  Courtesy of Teresa Wu, MD

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MORE SMALL PARTS PROBE ULTRASOUND

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Hip Effusion and Normal Comparison

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Gout: halo of fluid around tendon in foot

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Splinter – Wood is White

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Structures of the Volar Wrist

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Ulnar Nerve at Elbow

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Here’s the Bullet

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Retinal Ultrasound Pearls & Pitfalls by Teresa Wu, MD

• Ultrasound is useful in a patient whose retina may be obscured by blood, edema, cataracts, or opacification.
• Ultrasound is contraindicated in the presence of suspected globe rupture.
• Applying increased pressure will not enhance your image and could theoretically worsen an eye injury. Instead, apply more ultrasound gel to improve your interface.
• Higher resolution probes will provide you with better images. 7.5 MHz or 10 MHz transducers are best.
• Systematically obtain images of all four retinal quadrants by having the patient look up, down, left, and right during the scan. Make sure you get a clear view of the periphery where many occult findings can be missed.
• Always scan the contra-lateral eye for a comparison view.
• Do not leave the probe in contact with the eyelid for more than 60 seconds. Propagation of heat from the probe can coagulate the aqueous humor.
• Bear in mind that a posterior vitreous detachment (PVD) may look like a retinal detachment (RD) on ultrasound.

Normal Eye

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Retinal detachment

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more severe retinal detachment

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