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Case Of the Week #5

Right lower extremity cellulitis without abscess

In this young female who presented with 3 days of worsening lower extremity discomfort and swelling, the differential should include mostly focal causes of her swelling: trauma, hematoma, dvt, or cellulitis with or without abscess. Fortunately with a couple quick ultrasound exams, you can come to a definitive diagnosis.

She has risk factors for cellulitis (walking barefoot for extended periods of time) as well as DVT (long car ride, birth control). 

With her lower extremity swelling that spares above the knee, the most likely place for a DVT would be in the popliteal vessel. As you can see, the vessel compresses and therefore no dvt is seen in this area. Learn more about DVT exam here

Moving down the leg to the area of swelling/erythema/pain, the ultrasound can provide a tremendous amount of information to lead you to a diagnosis. And like with any ultrasound of legs or arms, there is a control side you can compare your findings to if you are unsure exactly what normal should look like.

Right leg

Cobblestoning - subcutaneous swelling due to edema surrounding adipose/soft tissue

Left leg

Normal appearing subcutaneous tissue without edema/cobblestoning

On the right leg, the subcutaneous tissue is very enlarged with hypoechoic edema surrounding pockets of adipose tissue/soft tissue, a "cobblestone" appearance. It is not specific to cellulitis. Can also see this in CHF, or early hematoma. But in the right clinical scenario it certainly can help rule out venous stasis or other red skin changes.

In one study of 126 emergency room patients, ER physicians were asked to categorize patients as pre-test probability suggesting they will need a drainage vs those patients they thought did not need any abscess drainage. Ultrasound overall changed management in 50% of cases!

Out of the 82 patients initially thought to not need any further drainage, ultrasound changed management in 39 of them (33 needed drainage, 6 needed consults/further testing). Out of the those 44 patients initially thought to need drainage, 16 did not need drainage after ultrasound.

Such a simple ultrasound exam that changed management in 50% of cases.

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