1. Correct Answer: C. Submerge the hand in a water bath

Rationale: Using ultrasound to assess abscesses, lacerations, or other pathology within the hand or foot can be difficult due to significant pain, anatomic restrictions, or other factors that limit the ability of the probe to make contact with the skin. Water baths can significantly decrease discomfort without compromising imaging quality. Warmed ultrasound gel would increase contact with the skin. While CT imaging or a hand surgery consult may also reveal an abscess, they take significantly more time and resources than using a simple water bath.

1. 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;22(7):589-593.

2. LeDonne S, Sengupta D. US probe: Ultrasound water bath for distal extremity evaluation. http://www.emdocs.net/us-probe-ultrasound-water-bath-for-distal-extremity-evaluation/

3. Shih J. Ultrasound for the win! 53M with right index finger swelling. https://www.aliem.com/2017/07/ultrasound-win-53m-right-index-finger-swelling/

2. Correct Answer: D. Posterior acoustic enhancement

Rationale: Because abscesses are fluid-filled spaces, ultrasound waves are less attenuated and hence tissues deep to the abscess appear hyperechogenic (posterior acoustic enhancement). “Dirty” shadowing suggests air or gas, which scatters ultrasound waves. “Clean” shadowing suggests a solid object that does not permit ultrasound waves to pass through, such as bone or gallstones. Cobblestoning suggests cellulitis without abscess.

1. O’Rourke K, Kibbee N, Stubbs A. Ultrasound for the evaluation of skin and soft tissue infections. Mo Med. 2015;112(3):202-205.

3. Correct Answer: A. No incision

Rationale: The image demonstrates cobblestoning without any signs of abscess. At ˜0.5 cm, the epidermis/dermis layer gives way to subcutaneous tissue, which in this case is filled with subcutaneous edema. Beyond 1.2 cm lies muscle. While Figure 79.2 is a single still image, there are no clear fluid collections, areas with septae or sediment, defined areas with significant posterior acoustic enhancement, or other signs of abscess. Therefore, no incision is indicated.