Not All Lumps Need a Scalpel: The Power of Soft Tissue Ultrasound
This article also appears in the Southern Medical Association News at this link.
Case Presentation
A 33-year-old male athlete presents to his primary care clinic with swelling, pain, and tenderness in his right axilla for 2 days. He denies fever or trauma. His past medical history is unremarkable. On exam, the area is warm, erythematous, and indurated. There is no crepitus, fluctuance, or drainage. His vital signs are normal. The provider is concerned about a possible abscess and is unsure whether incision and drainage (I&D) is warranted or if antibiotics alone would suffice. A point-of-care ultrasound (POCUS) is performed to answer this focused clinical question.
What do you see, and what’s the diagnosis?
Figure 1. View of the right axilla demonstrating thickened dermis and subcutaneous tissue and “cobblestoning” - tracking of anechoic fluid between hyperechoic strands of fat. There is no distinct fluid collection.
POCUS Findings
The ultrasound reveals no fluid collection. Instead, the subcutaneous tissue shows a “cobblestone” appearance (tracking of anechoic fluid between strands of fat), consistent with interstitial edema from cellulitis. There is no hypoechoic or anechoic pocket, no posterior acoustic enhancement, and no swirling of contents on compression—signs that would suggest an abscess.
Key POCUS findings for cellulitis:
1. Cobblestoning
2. Thickened dermis and subcutaneous fat skin layers
3. Hyperechoic appearance of the adipose tissue in comparison to the unaffected area
Normal POCUS appearance:
A normal soft tissue scan shows the skin, subcutaneous fat with thin echogenic strands, and underlying muscle layers with distinct architecture. There should be no hypoechoic or complex fluid collections, disruption of fascial planes, or increased echogenicity. Sometimes vascular structures could mimic an abscess, and that's why it is essential to scan in at least two planes. In one view, the vessel may appear round and resemble a fluid pocket, but in a longitudinal view, it will show as a linear or elongated structure. Additionally, using Color Mode can help confirm vascularity and prevent misdiagnosis. Figure 2 demonstrates a view of cellulitis next to a normal soft tissue scan on the same patient. Refer to Figure 3 for an annotated view of the soft tissue layers.
Figure 2. These side-by-side ultrasound images show an area of cellulitis on the left and normal soft tissue on the right. Both images were captured with the same settings—2.5 cm depth and identical gain. On the left, the dermis and epidermis are thickened, and the subcutaneous fat appears more hyperechoic and edematous. The muscle layer begins at a depth of 1.5 cm on the left, compared to just 0.5 cm on the right, highlighting significant soft tissue swelling in the affected area. Depth markers on the side indicate 1 cm with dashes and 0.5 cm with dots.
Figure 3. This annotated image demonstrates the typical appearance of normal soft tissue layers. Note the clearly defined dermis, subcutaneous fat, hyperechoic fascial planes, and striated muscle fibers between the fascial planes
What else can POCUS reveal in soft tissue scans?
POCUS doesn’t just help identify or rule out abscesses—it can reveal a variety of alternative or coexisting pathologies that may present similarly:
Lymph nodes: Typically appear as oval-shaped, hypoechoic structures with a central echogenic hilum. Vascularity may be detected while using Color mode.
Lipomas: These benign fatty tumors appear as well-defined, isoechoic to slightly hyperechoic lesions within the subcutaneous tissue, with a homogeneous internal texture and no internal vascularity or fluid.
Superficial thrombophlebitis or varicosities: POCUS can identify superficial vessels and clots, which might explain localized swelling or tenderness and are important to rule out before performing procedures.
Foreign bodies: Hyperechoic objects with posterior shadowing or reverberation artifacts can sometimes be identified, especially in cases of unclear trauma or recurrent infection.
Procedural guidance and follow-up with POCUS:
POCUS also adds value for patients who do require drainage:
Pre-procedure safety: It helps identify superficial vessels or other structures to avoid, ensuring safer and more precise incision planning.
Post-procedure confirmation: Repeat POCUS can confirm that the entire abscess cavity has been drained and that no residual pockets remain—an important step in preventing recurrence or incomplete treatment.
Evidence
POCUS provides high diagnostic accuracy in soft tissue infections, with studies reporting a sensitivity of 94–96% and specificity of 85–87% for detecting abscesses.[1–2] It’s especially useful when the physical exam is inconclusive—just like in the case presented in this article.
In one emergency department study by Tayal et al., POCUS changed management in 56% of patients who had an equivocal soft tissue exam.[3] Similarly, a primary care study found that ultrasound altered clinical decisions in 55% of cases, including whether to perform an I&D and how to approach it. Notably, it also increased procedural confidence in 52% of providers.[4]
For primary care, POCUS enables immediate decision-making, reduces unnecessary referrals and procedures, and enhances diagnostic certainty. Soft tissue ultrasound is also among the easiest applications to learn, making it a practical and high-yield skill for any clinician.
Explore other high-yield primary care applications of POCUS in this blog post. [5]
Case Resolution
The patient was treated with oral antibiotics, guided by the absence of an abscess on POCUS. At follow-up two days later, he reported improvement in swelling and redness. The infection resolved without the need for drainage.
Impact of POCUS
This case shows how POCUS brings speed, clarity, and confidence to managing soft tissue infections in primary care. It allows providers to individualize care, avoid unnecessary procedures, guide safe interventions, and even detect alternative diagnoses. In this instance, the patient avoided an unnecessary I&D and was able to resume his normal activities without the downtime or prolonged recovery often associated with surgical intervention. Additionally, in clinics that do not perform I&Ds, the provider may have referred this patient to the emergency department, which could have resulted in a costly, time-consuming, and burdensome experience for both the patient and the healthcare system.
Soft tissue infections are common, but not all lumps are created equal. POCUS empowers primary care providers to distinguish cellulitis from abscesses and other mimics at the bedside. With minimal training, providers can enhance diagnostic accuracy, avoid complications, and provide more efficient care. Whether you're deciding to lance or to leave alone, POCUS makes sure you’re not guessing.
At Hello Sono, we are committed to clinical excellence and efficiency. We build high-quality, compliant, and profitable POCUS programs to improve patient care and save overall healthcare costs. Access the POCUS ROI Calculators to see the financial impact of POCUS. Fill out the contact form to speak to an expert.
Authored by Tatiana Havryliuk, MD
References
Gottlieb M, Avila J, Chottiner M, Peksa GD. Point-of-Care Ultrasonography for the Diagnosis of Skin and Soft Tissue Abscesses: A Systematic Review and Meta-analysis [published correction appears in Ann Emerg Med. 2022 Jan;79(1):90. doi: 10.1016/j.annemergmed.2021.10.020.]. Ann Emerg Med. 2020;76(1):67-77. doi:10.1016/j.annemergmed.2020.01.004
Adams CM, Neuman MI, Levy JA. Point-of-Care Ultrasonography for the Diagnosis of Pediatric Soft Tissue Infection. J Pediatr. 2016;169:122-7.e1. doi:10.1016/j.jpeds.2015.10.026
Tayal VS, Hasan N, Norton HJ, Tomaszewski CA. The effect of soft-tissue ultrasound on the management of cellulitis in the emergency department. Acad Emerg Med. 2006;13(4):384-388. doi:10.1197/j.aem.2005.11.074
Greenlund LJS, Merry SP, Thacher TD, Ward WJ. Primary Care Management of Skin Abscesses Guided by Ultrasound. Am J Med. 2017;130(5):e191-e193. doi:10.1016/j.amjmed.2016.11.040
Havryliuk T. POCUS High-Yield Cases: How Ultrasound Changed the Plan. Hello Sono. https://www.hellosono.com/hello-sono-blog/pocus-high-yield-cases. Published February 22, 2024. Accessed April 18, 2025.