POCUS and Foreign Bodies

Written By: Will Perkins, MD. Edited by: Jeff Greco MD

Case

A 48 year old woman comes to ED for persistent pain in her finger for the past week after cleaning up broken glass. PE shows nothing.

Evidence

“Pooled sensitivity and specificity were, respectively, 72% (95% confidence interval [CI] = 57% to 83%) and 92% (95% CI = 88% to 95%).”

“Of the 166 foreign bodies inserted in total, 156 were detected by ultrasound. Ten sites were falsely analyzed as negative, for a sensitivity of 94%. There was one false positive result and 148 true negatives. The specificity was therefore 99%.“

Many studies have challenged radiologists to find varying sizes of wood/metal/glass splinters placed surreptitiously into human cadavers or pigs feet like a morbid easter egg hunt. Results varied.

Technique

Most foreign bodies are best viewed with a high frequency probe, favoring resolution over depth - choose linear or hockey stick. A water bath for hands or feet may help with visualization. The water transmits the sound waves without dirty useless air mucking up your images. Air is the worst. Ugh.

Foreign bodies may be visualized directly or indirectly. Look for a hyperechoic object especially with metal or glass FBs. Sometimes your only clue is posterior shadowing or focal edema.