Ultrasound features of purulent skin and soft tissue infection without abscess

Prospective evaluation of ultrasound features of magnesium-based bioabsorbable screw resorption in pediatric fractures

OBJECTIVE

Bioabsorbable magnesium-based alloy screws release gas upon resorption. The resulting findings in the adjacent soft tissues and joints may mimic infection. The aim of the study was to evaluate the ultrasound (US) findings in soft tissues and joints during screw resorption.

METHODS

Prospectively acquired US studies from pediatric patients treated with magnesium screws were evaluated for screw head visibility, posterior acoustic shadowing, twinkling artifact, foreign body granuloma, gas (soft tissue, intra-articular), alterations of the skin and subcutaneous fat, perifascial fluid, localized fluid collections, hypervascularization, and joint effusion.

RESULTS

Sixty-six US studies of 28 pediatric patients (nfemale = 9, nmale = 19) were included. The mean age of the patients at the time of surgery was 10.84 years; the mean time between surgery and ultrasound was 128.3 days (range = 6-468 days). The screw head and posterior acoustic shadowing were visible in 100% of the studies, twinkling artifact in 6.1%, foreign body granuloma in 92.4%, gas locules in soft tissue in 100% and intra-articular in 18.2%, hyperechogenicity of the subcutaneous fat in 90.9%, cobblestoning of the subcutaneous fat in 24.2%, loss of normal differentiation between the epidermis/dermis and the subcutaneous fat in 57.6%, localized fluid collection in 9.9%, perifascial fluid in 12.1%, hypervascularization in 27.3%, and joint effusion in 18.2%.

CONCLUSION

US findings in pediatric patients treated with magnesium screws strongly resemble infection, but are normal findings in the setting of screw resorption.

CLINICAL RELEVANCE STATEMENT

Bioabsorbable magnesium-based alloy screws release gas during resorption. The resulting US findings in the adjacent soft tissues and joints in pediatric patients may mimic infection, but are normal findings.

KEY POINTS

• Bioabsorbable magnesium-based alloy screws release gas upon resorption. • The resulting ultrasound findings in children's soft tissues and joints closely resemble those of soft tissue infection or osteosynthesis-associated infection. • Be familiar with these ultrasound findings in order to avoid inadvertently misdiagnosing a soft tissue infection or osteosynthesis-associated infection.

Validation of a Clinical Decision Rule for Ultrasound Identification of MRSA Skin Abscesses in Children

OBJECTIVE

The aim of this study was to validate an adult-derived clinical decision rule for ultrasound identification of methicillin-resistant Staphylococcus aureus (MRSA) skin abscesses in a pediatric cohort.

METHODS

We conducted a retrospective study of skin and soft tissue infections in patients <21 years presenting to the emergency department who had radiology performed ultrasounds completed and wound cultures obtained. Ultrasound scans were reviewed for edge definition, volume, and shape by 2 pediatric emergency physicians with expertise in point-of-care ultrasound, with approximately 25% of scans reviewed by both experts to evaluate interrater reliability. A third, blinded expert weighed in for discrepancies before analysis. Test performance characteristics were calculated for the clinical decision rule in children.

RESULTS

Two hundred nine patients were enrolled, with mean age of 9.8 (±6.7) years; 87 (42%) were male. Sixty-nine (33%) patients had a wound culture positive for MRSA. The clinical decision rule had a sensitivity of 86% (95% confidence interval [CI], 75%-93%), specificity of 32% (95% CI, 25%-41%), positive predictive value of 38% (95% CI, 35%-42%), negative predictive value of 82% (95% CI, 71%-89%), positive likelihood ratio of 1.26 (95% CI, 1.08-1.46), negative likelihood ratio of 0.45 (95% CI, 0.24-0.84), and an odds ratio of 2.8 (95% CI, 1.31-5.97).

CONCLUSIONS

This clinical decision rule for ultrasound identification of MRSA abscesses had moderately high sensitivity and negative predictive value in pediatric patients, with similar sensitivity compared with the original adult validation group. Ultrasound may help identify MRSA abscesses, allowing for improved antibiotic choices and outcomes for children with MRSA abscesses.

Common Ultrasound Applications for Pediatric Musculoskeletal Conditions

PURPOSE OF REVIEW

To discuss the use of ultrasound for diagnosis and management of common pediatric musculoskeletal conditions through a case-based approach.

RECENT FINDINGS

Ultrasound is an essential diagnostic modality in the early detection of developmental dysplasia of the hips and can be used as early as 6 weeks of age when the ossific nucleus has not developed yet. Ultrasound is helpful in diagnosing traumatic injuries such as fractures and intramuscular hematomas, can visualize fracture healing at early stages, and can also be used to guide aspiration of hematomas that can help with decreasing pain and faster recovery. Ultrasound is superior to radiographs in evaluating joint effusions and soft tissue infections or masses and is better tolerated by children compared to other imaging modalities such as magnetic resonance imaging (MRI). Ultrasound is an easily accessible, affordable, non-invasive, and radiation-free imaging modality that is well tolerated by children and their families. It can aid in the diagnosis and management of a wide variety of musculoskeletal conditions including developmental, traumatic, and infectious etiologies, as well as in the evaluation of superficial soft tissue masses.

To Drain or not to Drain? Point-of-care Ultrasound to Investigate an Axillary Mass: Case Report

Introduction: Point-of-care ultrasound (POCUS) has great sensitivity in the diagnosis of abscesses and swollen lymph nodes. Many studies outline the characteristics that distinguish abscesses from lymph nodes on POCUS. Case Report: We present a case from the emergency department in which a patient presented with a potential abscess but was found to have a malignant lymph node on imaging. Conclusion: Point-of-care ultrasound can be used to differentiate an abscess from a swollen lymph node. Abscesses are generally anechoic or hypoechoic with septae, sediment or gas contents, and they lack internal vascularity. Benign lymph nodes are echogenic with hypoechoic cortex with hilar vascularity.

Pediatric chest wall masses: spectrum of benign findings on ultrasound

A palpable finding along the chest wall is a frequent indication for pediatric US. Accurate identification of benign lesions can reassure families and appropriately triage children who need follow-up, cross-sectional imaging, or biopsy. In this pictorial essay, we review chest wall anatomy, illustrate US techniques and discuss key US imaging features of common benign lesions and normal variants.

Application of contrast-enhanced ultrasound in the diagnosis of burn depth

Background

The diagnosis of burn depth often relies on the subjective judgment of plastic surgeons. Contrast-enhanced ultrasound (CEUS) can visualize the microcirculation well and has potential value in diagnosing the depth of burn wounds. We assessed the depth of the burn wounds by CEUS, and compared the results with histological examination.

Methods

Two rhesus monkeys were used, and multiple burn wounds with different depths were made on their backs. The echo of the dermis and subcutaneous tissue were observed for each wound, and the thickness of the dermis was measured. CEUS was performed to evaluate the depth of burn wounds and compared with pathological results.

Results

(I) After scalding, dermal tissue edema occurred, and the thickness of the dermis measured by a US tended to increase gradually, related to the time of scalding and the order of measurement. (II) With the prolongation of the burn time, the depth of filling by contrast agent gradually increased, from the superficial dermis to the deep dermis and subcutaneous tissue, indicating that the depth of tissue damage gradually increased. This was consistent with the pathological observation. The thickness of the healthy dermis was about 1.3-1.8 mm, and 2.7-4.1 mm after scalding. The depth of the burn wounds was 0.9-4.1 mm, accounting for 32-100% of the full skin thickness.

Conclusions

CEUS is a convenient and fast examination method that is consistent with pathological diagnosis of the depth of burn wounds and could prove valuable for the accurate assessment of burn injuries.

Impact of Emergency Medicine Point-of-Care Ultrasound on Radiology Ultrasound Volumes in a Single Pediatric Emergency Department

PURPOSE

Point-of-care ultrasound (POCUS) is growing, but few data exist regarding its effects on radiology ultrasound (Rad US) volumes. The authors studied changes in Rad US ordered by emergency medicine (EM) as POCUS began and grew at their pediatric hospital.

METHODS

This retrospective study included EM POCUS and EM-ordered Rad US volumes between 2011 and 2017, during three 2-year intervals: before POCUS, early POCUS, and expanded POCUS. Changes in overall Rad US and POCUS volumes per visit during these intervals were studied. Changes in skin and soft tissue infection (SSTI) US per SSTI visit, an examination performed diagnostically by both radiology and EM, were also assessed. Volume differences were examined using the Mann-Whitney U test (significance threshold, P < .05), and process control charts were used to identify nonrandom variations.

RESULTS

The study included 49,908 Rad US and 2,772 POCUS examinations during 647,890 emergency department visits. Rad US volumes per visit remained unchanged during early POCUS (P = .858) but increased with expanded POCUS (P < .005). A transient nonrandom increase in Rad US occurred as POCUS began. SSTI Rad US per SSTI visit significantly increased (P < .001) during early POCUS but did not change with expanded POCUS (P = .143). An SSTI management pathway in the emergency department before expanded POCUS may have affected ordering. Other variation occurred in proximity to practice changes and seasonal patterns.

CONCLUSIONS

Rad US overall and specifically for SSTI increased or remained stable during the introduction and growth of EM POCUS. Rather than decreasing Rad US, EM POCUS had a complementary role.

Interpretation Accuracy and Interrater Agreement of Pediatric Skin and Soft Tissue Point-of-Care Ultrasound Images among Residents and Faculty

BACKGROUND

Point-of-care ultrasound (POCUS) is commonly used to facilitate care in the emergency department. Acquired images are often reviewed by local experts for educational and quality assurance purposes. However, no published study has examined the accuracy and reliability of POCUS image interpretation by multiple reviewers.

OBJECTIVES

We studied the accuracy and interrater agreement among expert and trainee reviewers of prerecorded pediatric skin and soft tissue (SST) POCUS images.

METHODS

POCUS faculty and emergency medicine (EM) residents blindly reviewed deidentified pediatric SST POCUS images and indicated whether a drainable fluid collection was present, absent, or indeterminate. This was then compared with the gold standard based on discharge diagnoses and telephone follow-up. Images rated as indeterminate were excluded from the initial analysis. Sensitivity analysis assuming indeterminate answers were inaccurate was subsequently conducted.

RESULTS

In phase 1, 6 pediatric EM POCUS directors reviewed 168 images. The overall accuracy was 79.7% (range 66.1-86.0%). The mean Cohen's kappa was 0.58 (range 0.24-0.84). Sensitivity analysis yielded an overall accuracy of 71.3% (range 56.5-76.9%) and a Cohen's kappa of 0.43 (range 0.20-0.59). In phase 2, 6 general EM POCUS faculty and 20 EM residents reviewed 120 images. The overall accuracy among residents was 72.2% (range 51.4-84.7%) and among faculty was 83.6% (range 77.9-88.8%). Sensitivity analysis yielded an overall resident accuracy of 63.0% (range 49.5-80.7) and an overall faculty accuracy of 73.9% (range 67.0-79.8%). Fleiss' kappa was 0.322 for residents and 0.461 for faculty.

CONCLUSIONS

We found moderate accuracy and fair to good interrater agreement among POCUS faculty and EM residents reviewing pediatric SST POCUS images.

Ultrasound-triggered breast tumor sonodynamic therapy through hematoporphyrin monomethyl ether-loaded liposome

Sonodynamic therapy (SDT) which employs ultrasound-triggered sonosensitizers to generate reactive oxygen species (ROS) has been proved to be effective for treatment of cancers. However, it is still desirable for sonosensitizers to be delivered to tumors as effectively as possible. In this study, we prepared the hematoporphyrin monomethyl ether (HMME)-loaded liposome as the sonosensitizers for SDT and evaluated their effects on human MCF-7 breast cancer cells in vitro and in vivo. Liposomes prepared by thin film hydration technique were about 100 nm in size with positive zeta potential and exhibited spherical in shape. Following irradiation of ultrasound which generates intracellular ROS, the liposome facilitated the delivery of HMME to tumor cells. HMME-loaded liposomes showed low cytotoxicity under basal condition but significant sonodynamic effects under ultrasonic irradiation. Notably, HMME-loaded liposomes exhibited spatial distribution of HMME in tumor tissues of mice. The promoted delivery of HMME into the tumors by liposomes was shown by the greater tumor growth inhibition than free HMME after 20-day treatment. Taken together, these results show that HMME-loaded liposome functions as a promising sonosensitizer for SDT, implying the efficient antitumor effects of HMME-based SDT on breast tumor.