Wednesday Image Review

What’s the Diagnosis? By Dr. Daniel Petrosky

50-year-old with a history of T2DM, hypertension, hyperlipidemia, substance use, and asthma who presents with 4 weeks of progressive left index finger pain. The patient had some swelling from the fall, but now has had one week of swelling worsening, pain, redness. Physical exam reveals digit red, swollen, fusiform, very tender, and unable to flex or extend DIP and PIP. A POCUS is obtained and shown below. What’s the diagnosis?

Answer: Necrotizing Fasciitis

POCUS is very quick to evaluate for many of differentials but would be painful to press directly on the digit with gel. There is an excellent alternative here: waterbath technique.

Water is an excellent medium for ultrasound. In this instance, we submerged the patient’s hand in water, and we are able to submerge the probe and hover above the affect area without concern for the amount of gel we displace in assessing the area or the pressure we apply to get clear images. Also, the high transmissibility of ultrasound through water allows for excellent visibility of superficial structures of body parts like fingers when direct contouring with gel would be virtually impossible. With this technique, we can look for fractures, abscesses, air, and cobble-stoning quickly, easily and with a high degree of accuracy.

So, in this patient as it turns out, air and cellulitis are visible, likely being a necrotizing infection. POCUS with a waterbath was the quickest way to establish this diagnosis. This is extremely important because even with advances in antibiotics, time to surgical intervention is most important in decreasing morbidity and mortality in these patients.


Blaivas M, Lyon M, Brannam L, Duggal S, Sierzenski P. Water bath evaluation technique for emergency ultrasound of painful superficial structures. Am J Emerg Med. 2004 Nov;22(7):589-93. doi: 10.1016/j.ajem.2004.09.009. PMID: 15666267.

Shelhoss S C, Burgin C M (November 16, 2022) Maximizing Foreign Body Detection by Ultrasound With the Water Bath Technique Coupled With the Focal Zone Advantage: A Technical Report. Cureus 14(11): e31577. doi:10.7759/cureus.31577

Shrimal P, Bhoi S, Sinha TP, Murmu LR, Nayer J, Ekka M, Mishra P, Kumar A, Trikha V, Aggarwal P. Sensitivity and specificity of waterbath ultrasound technique in comparison to the conventional methods in diagnosing extremity fractures. Am J Emerg Med. 2022 Mar;53:118-121. doi: 10.1016/j.ajem.2021.12.067. Epub 2022 Jan 2. PMID: 35016093.

Bonne SL, Kadri SS. Evaluation and Management of Necrotizing Soft Tissue Infections. Infect Dis Clin North Am. 2017 Sep;31(3):497-511. doi: 10.1016/j.idc.2017.05.011. PMID: 28779832; PMCID: PMC5656282.

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