Point-of-care ultrasound in skin and soft tissue infections.

BACKGROUND: Skin and soft tissue infections (SSTIs) are commonly encountered in clinical practice. Point-of-care ultrasound (POCUS) is becoming an increasingly valuable tool in hospital medicine, especially with advancements in ultrasound technology that make it easier to perform. POCUS can augment the history and physical exam in patients with suspected SSTIs. POCUS can detect deeper infections, such as abscesses, and expedite time to surgical debridement for life-threatening infections such as necrotizing fasciitis (NF). OBJECTIVES: This review provides an introduction on how to perform and interpret a skin and soft tissue POCUS exam, the key sonographic findings for SSTIs, and how to incorporate these findings into clinical reasoning and management. METHODS: SSTI POCUS literature was reviewed using PubMed. All relevant studies with a defined protocol and reported sensitivity and specificity pertaining to the use of POCUS to diagnose SSTIs in adults were included. The authors provide additional input based on their ultrasound expertise and clinical experience. RESULTS: A total of seven studies met the criteria to be included in this review. CONCLUSIONS: Soft tissue POCUS is a valuable tool for hospitalists to improve diagnostic accuracy and patient care when assessing suspected SSTIs. Access to equipment, POCUS training, and experience are barriers to widespread use. However, performing a soft tissue POCUS exam is straightforward. It requires less training compared to other POCUS exams, and it has notable potential for routine future practice in the evaluation and management of suspected SSTIs and other dermatologic conditions.

Imaging features of soft-tissue infections.

Skin and soft tissues are among the most common sites of infections. Infections can involve the superficial epidermis to deep muscles and bones. Most infections spread through contiguous structures, although hematogenous spread can occur in the setting of an immunocompromised state and with atypical infections. While clinical diagnosis of infections is possible, it often lacks specificity, necessitating the use of imaging for confirmation. Cross-sectional imaging with US, CT, and MRI is frequently performed not just for diagnosis, but to delineate the extent of infection and to aid in management. Nonetheless, the imaging features have considerable overlap, and as such, it is essential to integrate imaging features with clinical features for managing soft tissue infections. Radiologists must be aware of the imaging features of different infections and their mimics, as well as the pros and cons of each imaging technique to properly use them for appropriate clinical situations. In this review, we summarize the most recent evidence-based features of key soft tissue infections.

Real-time identification of life-threatening necrotizing soft-tissue infections using indocyanine green fluorescence imaging.

Significance: Necrotizing soft-tissue infections (NSTIs) are life-threatening infections with a cumulative case fatality rate of 21%. The initial presentation of an NSTI is non-specific, frequently leading to misdiagnosis and delays in care. No current strategies yield an accurate, real-time diagnosis of an NSTI. Aim: A first-in-kind, observational, clinical pilot study tested the hypothesis that measurable fluorescence signal voids occur in NSTI-affected tissues following intravenous administration and imaging of perfusion-based indocyanine green (ICG) fluorescence. This hypothesis is based on the established knowledge that NSTI is associated with local microvascular thrombosis. Approach: Adult patients presenting to the Emergency Department of a tertiary care medical center at high risk for NSTI were prospectively enrolled and imaged with a commercial fluorescence imager. Single-frame fluorescence snapshot and first-pass perfusion kinetic parameters-ingress slope (IS), time-to-peak (TTP) intensity, and maximum fluorescence intensity (IMAX)-were quantified using a dynamic contrast-enhanced fluorescence imaging technique. Clinical variables (comorbidities, blood laboratory values), fluorescence parameters, and fluorescence signal-to-background ratios (SBRs) were compared to final infection diagnosis. Results: Fourteen patients were enrolled and imaged (six NSTI, six cellulitis, one diabetes mellitus-associated gangrene, and one osteomyelitis). Clinical variables demonstrated no statistically significant differences between NSTI and non-NSTI patient groups (p-value≥0.22). All NSTI cases exhibited prominent fluorescence signal voids in affected tissues, including tissue features not visible to the naked eye. All cellulitis cases exhibited a hyperemic response with increased fluorescence and no distinct signal voids. Median lesion-to-background tissue SBRs based on snapshot, IS, TTP, and IMAX parameter maps ranged from 3.2 to 9.1, 2.2 to 33.8, 1.0 to 7.5, and 1.5 to 12.7, respectively, for the NSTI patient group. All fluorescence parameters except TTP demonstrated statistically significant differences between NSTI and cellulitis patient groups (p-value<0.05). Conclusions: Real-time, accurate discrimination of NSTIs compared with non-necrotizing infections may be possible with perfusion-based ICG fluorescence imaging.

Ultrasonography for the Detection of Osteomyelitis in Pediatric Patients With Soft Tissue Infection: A Pilot Study.

OBJECTIVES: To demonstrate the usefulness of ultrasonography for differentiating soft tissue infections with or without osteomyelitis in pediatric patients who underwent ultrasonography and subsequent magnetic resonance imaging (MRI). METHODS: Twenty-three patients were classified into 2 groups: 12 patients with and 11 patients without osteomyelitis based on MRI. Osteomyelitis using ultrasound is characterized by the presence of bone cortex irregularity and/or subperiosteal abscess formation. The diagnostic performance of ultrasonography for detecting osteomyelitis and subperiosteal abscess formation was compared with that of MRI. Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were calculated with 95% confidence intervals (CIs). RESULTS: Of 12 osteomyelitis cases, 11 had abnormal bone marrow enhancement (one residual case did not undergo contrast enhancement study) and 5 had subperiosteal abscesses. The diagnostic accuracy of ultrasonography for osteomyelitis was 82.6% (number of correct diagnosis of osteomyelitis/total number = 19/23; 95% CI, 61.2-95.0) and for detecting periosteal abscess was 95.7% (number of correct diagnosis of periosteal abscess/total number = 22/23; 95% CI, 78.1-99.9), respectively. The sensitivity and specificity of ultrasonography for detecting osteomyelitis were 66.7% (95% CI, 34.9-90.1) and 100% (95% CI, 71.5-100), respectively. The sensitivity and specificity of ultrasonography for detecting periosteal abscess were 80% (95% CI, 28.4-99.5), and 100% (95% CI, 81.5-100), respectively. One-third of osteomyelitis cases could not be detected using ultrasonography. CONCLUSIONS: Ultrasonography may be useful for diagnosing osteomyelitis in pediatric patients; however, the technique appears limited by low sensitivity. However, it is more accurate for diagnosis of periosteal abscess in these patients.

No role for standard imaging workup of patients with clinically evident necrotizing soft tissue infections: a national retrospective multicenter cohort study.

PURPOSE: To assess the diagnostic contribution of different imaging studies to diagnose necrotizing soft tissue infections (NSTIs) and the time to surgery in relation to imaging with the hypothesis that imaging studies may lead to significant delays without being able to sufficiently dismiss or confirm the diagnosis since a NSTI is a surgical diagnosis. METHODS: A retrospective multicenter cohort study of all NSTI patients between 2010 and 2020 was conducted. The primary outcome was the number of cases in which imaging contributed to or led to change in treatment. The secondary outcomes were time to treatment determined by the time from presentation to surgery and patient outcomes (amputation, intensive care unit (ICU) admission, length of ICU stay, hospital stay, and mortality). RESULTS: A total of 181 eligible NSTI patients were included. The overall mortality was 21% (n = 38). Ninety-eight patients (53%) received imaging in the diagnostic workup. In patients with a clinical suspicion of a NSTI, 81% (n = 85) went directly to the operating room and 19% (n = 20) underwent imaging before surgery; imaging was contributing in only 15% (n = 3) by ruling out or determining underlying causes. In patients without a clinical suspicion of a NSTI, the diagnosis of NSTI was considered in 35% and only after imaging was obtained. CONCLUSION: In patients with clinically evident NSTIs, there is no role for standard imaging workup unless it is used to examine underlying diseases (e.g., diverticulitis, pancreatitis). In atypical presenting NSTIs, CT or MRI scans provided the most useful information. To prevent unnecessary imaging and radiation and not delay treatment, the decision to perform imaging studies in patients with a clinical suspicion of a NSTI must be made extremely careful.

Lower extremity infections: Essential anatomy and multimodality imaging findings.

In modern practice, imaging plays an integral role in the diagnosis, evaluation of extent, and treatment planning for lower extremity infections. This review will illustrate the relevant compartment anatomy of the lower extremities and highlight the role of plain radiographs, CT, US, MRI, and nuclear medicine in the diagnostic workup. The imaging features of cellulitis, abscess and phlegmon, necrotizing soft tissue infection, pyomyositis, infectious tenosynovitis, septic arthritis, and osteomyelitis are reviewed. Differentiating features from noninfectious causes of swelling and edema are discussed.

Musculoskeletal infections through direct inoculation.

Musculoskeletal infections consist of different clinical conditions that are commonly encountered in daily clinical settings. As clinical findings and even laboratory tests cannot always be specific, imaging plays a crucial role in the diagnosis and treatment of these cases. Musculoskeletal infections most commonly occur secondary to direct inoculation into the skin involuntarily affected by trauma, microorganism, foreign bodies, or in diabetic ulcers; direct infections can also occur from voluntary causes due to surgery, vaccinations, or other iatrogenic procedures. Hematogenous spread of infection from a remote focus can also be a cause for musculoskeletal infections. Risk factors for soft tissue and bone infections include immunosuppression, old age, corticosteroid use, systemic illnesses, malnutrition, obesity, and burns. Most literature discusses musculoskeletal infections according to the diagnostic tools or forms of infection seen in different soft tissue anatomical planes or bones. This review article aims to evaluate musculoskeletal infections that occur due to direct inoculation to the musculoskeletal tissues, by focusing on the traumatic mechanism with emphasis on the radiological findings.

Ultrasonography for Skin and Soft Tissue Infections, Noninfectious Cysts, Foreign Bodies, and Burns in the Critical Care Setting.

There are multiple opportunities for the use of ultrasonography in the diagnosis of skin and soft tissue differentials. Ultrasonography is inexpensive, easily reproducible, and able to provide real-time data in situations where condition changes and progression are common. Not only does bedside ultrasonography provide the clinician an in-depth look beyond epidermal structures into body cavities, it remains a safe, nonionizing radiating, effective, cost-efficient, reliable, and accessible tool for the emergency management of life- and limb-threatening integumentary infections. Unnecessary invasive procedures are minimized, providing improved patient outcomes. Integumentary abnormalities secondary to trauma, surgery, and hospitalization are common among critical care patients. This article provides a brief overview and evidence-based recommendations for the use of ultrasonography in the critical care setting for integumentary system conditions, including common skin and soft tissue differentials, foreign bodies, and burn depth assessment.

Emphysematous Osteomyelitis of the Pubis Associated With Necrotizing Soft Tissue Infection of the Thigh.

Emphysematous osteomyelitis (EO) is a rare condition identified through the presence of intraosseous gas. It is frequently fatal even with prompt recognition and management. We report a case of EO presenting with a necrotizing soft tissue infection of the thigh in the setting of prior pelvic radiation. The purpose of this study was to highlight the unusual association between EO and necrotizing soft tissue infection.

Spectrum of imaging findings in soft-tissue necrosis.

Soft tissue necrosis can occur at different tissue levels, with numerous underlying causes. In this pictorial review, we highlight myonecrosis, and its accompanying stages, fat necrosis, devitalized soft tissue seen with infection, and necrotizing soft tissue infections. Imaging examples are provided with each entity.

CT utilization in evaluation of skin and soft tissue extremity infections in the ED: Retrospective cohort study.

OBJECTIVE: Skin and soft tissue infections (SSTI) are commonly diagnosed in the emergency department (ED). While most SSTI are diagnosed with patient history and physical exam alone, ED clinicians may order CT imaging when they suspect more serious or complicated infections. Patients who inject drugs are thought to be at higher risk for complications from SSTI and may undergo CT imaging more frequently. The objective of this study is to characterize CT utilization when evaluating for SSTI in ED patients particularly in patients with intravenous drug use (IVDU), the frequency of significant and actionable findings from CT imaging, and its impact on subsequent management and ED operations. METHODS: We performed a retrospective analysis of encounters involving a diagnosis of SSTI in seven EDs across an integrated health system between October 2019 and October 2021. Descriptive statistics were used to assess overall trends, compare CT utilization frequencies, actionable imaging findings, and surgical intervention between patients who inject drugs and those who do not. Multivariable logistic regression was used to analyze patient factors associated with higher likelihood of CT imaging. RESULTS: There were 4833 ED encounters with an ICD-10 diagnosis of SSTI during the study period, of which 6% involved a documented history of IVDU and 30% resulted in admission. 7% (315/4833) of patients received CT imaging, and 22% (70/315) of CTs demonstrated evidence of possible deep space or necrotizing infections. Patients with history of IVDU were more likely than patients without IVDU to receive a CT scan (18% vs 6%), have a CT scan with findings suspicious for deep-space or necrotizing infection (4% vs 1%), and undergo surgical drainage in the operating room within 48 h of arrival (5% vs 2%). Male sex, abnormal vital signs, and history of IVDU were each associated with higher likelihood of CT utilization. Encounters involving CT scans had longer median times to ED disposition than those without CT scans, regardless of whether these encounters resulted in admission (9.0 vs 5.5 h), ED observation (5.5 vs 4.1 h), or discharge (6.8 vs 2.9 h). DISCUSSION: ED clinicians ordered CT scans in 7% of encounters when evaluating for SSTI, most frequently in patients with abnormal vital signs or a history of IV drug use. Patients with a history of IVDU had higher rates of CT findings suspicious for deep space infections or necrotizing infections and higher rates of incision and drainage procedures in the OR. While CT scans significantly extended time spent in the ED for patients, this appeared justified by the high rate of actionable findings found on imaging, particularly for patients with a history of IVDU.

Imaging of Soft Tissue Infections.

Although superficial infections can often be diagnosed and managed clinically, physical examination may lack sensitivity and specificity, and imaging is often required to evaluate the depth of involvement and identify complications. Depending on the area of involvement, radiography, ultrasound, CT, MR imaging, or a combination of imaging modalities may be required. Soft tissue infections can be nonnecrotizing or necrotizing, with the later having a morbid and rapid course. Infectious tenosynovitis most commonly affects the flexor tendon sheaths of the hand, characterized by thickened and enhancing synovium with fluid-filled tendon sheaths.

POINT-OF-CARE ULTRASOUND IN THE EARLY DIAGNOSIS OF NECROTIZING FASCIITIS.

OBJECTIVE: The aim: To detect the ultrasonographic signs of necrotizing fasciitis (NF) suitable for its early diagnosis. PATIENTS AND METHODS: Materials and methods: Eigty two patients with soft tissue infection, including 14 with necrotizing faciitis, were examined by ultrasonography at the admission. Ultrasonografic features were compared to intraoperative findings by the same surgeon. RESULTS: Results: The thickening of subcutaneous tissue had high sensitivity (100%), but low specificity (5.8%). The hypoechoic and hyperechoic zones had the shape of "cobblestone" with sensitivity - 78.5%, specificity - 33.8%. Higher specificity (69.1%) had sign of "cobblestone separation" on two layers. The presence of fluid above the fascia (sensitivity - 71.4%; specificity - 69.1%), thickening of the fascia (sensitivity - 85.7%; specificity - 58.8%), indistinctness of the fascia edges (sensitivity - 85.7%; specificity - 66.1%) and loss of fascial homogeneity (sensitivity - 71.4%, specificity - 66.1%) were noted in early stages of NF. Advanced cases of NF were accompanied by the dissection of thick¬ened fascia with a strip of fluid (sensitivity - 57.1%, specificity - 92.6%) and accumulation of a fluid under the fascia (sensitivity - 28.5%, specificity - 95.5%). The muscles thickening (sensitivity - 28.5%; specificity - 67.6%), skin thickening (sensitivity - 57.1%; specificity - 58.8%), and loss of the skin's lower edge clarity (sensitivity - 57.1%; specificity - 63.2%) don't have diagnostic value without other signs of NF. CONCLUSION: Conclusions: Point-of-care ultrasonography allows visualization of soft tissue changes that may be hidden in the initial stages of necrotizing fasciitis and should be recommended for implementation as mandatory method of examination in patients with suspected surgical soft tissue infection.

ACR Appropriateness Criteria® Suspected Osteomyelitis, Septic Arthritis, or Soft Tissue Infection (Excluding Spine and Diabetic Foot): 2022 Update.

Musculoskeletal infections involve bones, joints, and soft tissues. These infections are a common clinical scenario in both outpatient and emergent settings. Although radiography provides baseline findings, a multimodality approach is often implemented to provide more detailed information on the extent of infection involvement and complications. MRI with intravenous contrast is excellent for the evaluation of musculoskeletal infections and is the most sensitive for diagnosing osteomyelitis. MRI, CT, and ultrasound can be useful for joint and soft tissue infections. When MRI or CT is contraindicated, bone scans and the appropriate utilization of other nuclear medicine scans can be implemented for aiding in the diagnostic imaging of infection, especially with metal hardware and arthroplasty artifacts on MRI and CT. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Anatomic and Treatment Descriptive Features of Foot Infections Presenting With Radiographic Soft Tissue Emphysema.

Foot infections associated with soft tissue emphysema, or the radiographic appearance of gas, are widely considered to necessitate urgent decompression with excisional debridement of the necrotic and infectious tissue burden. The objective of this investigation was to describe anatomic features and clinical outcomes associated with the presence of soft tissue emphysema in foot infections. A retrospective chart review was performed of 62 subjects meeting selection criteria. These were primarily male (74.2%), with a history of diabetes mellitus (85.5%), and without a history of previous lower extremity revascularization (98.4%). The primary radiographic location of the soft tissue emphysema was most frequently in the forefoot (61.3%), followed by the midfoot (21.0%), and rearfoot (16.1%). The soft tissue emphysema was most frequently observed primarily in the dorsal foot tissue (49.2%), followed by both dorsal and plantar foot tissue (27.4%), and the plantar foot tissue (24.2%). The soft tissue emphysema was confined to the primary anatomic location in 74.2% of subjects, while 25.8% of cases demonstrated extension into a more proximal anatomic area. Eighty-two percent of subjects underwent a bedside incision and drainage procedure on presentation in the emergency department, and 95.2% underwent a formal incision and drainage procedure in the operating room at 1.05 ± 0.79 (0-5) postadmission days. Twenty-seven percent of subjects had an unplanned 30-day readmission and 17.7% underwent an unplanned reoperation within 30 days following the index discharge. Fifty-two percent of subjects underwent a minor or major amputation during the index admission, while 33.9% eventually resulted in major limb amputation within 12 months. We hope that this investigation adds to the body of knowledge and provides expectations with respect to the evaluation and treatment of foot soft tissue infections complicated by the presence of radiographic soft tissue emphysema.

Role of point-of-care ultrasound (POCUS) in the diagnosis of an abscess in paediatric skin and soft tissue infections: a systematic review and meta-analysis.

AIMS: To evaluate the effect of point-of-care ultrasound (POCUS) for the diagnosis of an abscess and to compare the diagnostic accuracy of POCUS and physical examination (PE) in paediatric patients with skin and soft tissue infections (SSTI) in the emergency department. MATERIAL AND METHODS: A comprehensive literature search was carried out to identify Englishlanguage studies on POCUS for differentiating an abscess from cellulitis in paediatric patients with SSTI. The quality of the study was assessed by the Quality Assessment of Diagnostic Accuracy Studies 2 tool, and pooled sensitivity and specificity of various POCUS findings were determined. RESULTS: Seven studies with a total of 870 patients were included. There was significant heterogeneity across the included studies. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio for the diagnosis of abscess by POCUS were 0.90 (95% confidence interval [CI], 0.82-0.95), 0.80 (95% CI, 0.72-0.86), 4.5 (95% CI, 3.1-6.4), 0.13 (95% CI, 0.07-0.23), and 36 (95% CI, 17-75), respectively, with an area under the curve (AUC) was 0.89 (95% CI, 0.86-0.91). Four studies provided data regarding the PE method. The pooled sensitivity, specificity, and AUC of PE for the abscess were 0.84 (95% CI, 0.80-0.88), 0.69 (95% CI, 0.62-0.76), and 0.85 (95% CI, 0.81-0.88). CONCLUSIONS: POCUS is useful in identifying abscesses in paediatric patients with SSTI in emergency department, especially when PE is equivocal and outperforms PE alone.

Diagnostic performance of MRI and CT in diagnosing necrotizing soft tissue infection: a systematic review.

OBJECTIVE: To systematically review the accuracy of MRI and CT in diagnosing necrotizing soft tissue infection (NSTI). METHODS: MEDLINE and Embase were searched for original studies which reported the diagnostic performance of MRI or CT in detecting NSTI. Individual study quality was assessed using the QUADAS-2 tool. Sensitivity and specificity of MRI and CT were calculated and, if supported by data from at least two studies, pooled using a bivariate random-effects model. RESULTS: Six MRI studies and 7 CT studies were included. There were no major concerns with regard to study quality and applicability. The included studies used multiple diagnostic criteria, with sensitivities and specificities of both MRI and CT ranging between 0 and 100%. T2 hyperintensity of deep fascia was the most commonly used diagnostic MRI criterion (5 studies), yielding a pooled sensitivity of 86.4% (95% confidence interval [CI] 76.1-92.7%) and a pooled specificity of 65.2% (95% CI 35.4-86.6%). Presence of gas was the most commonly used diagnostic CT criterion (3 studies), yielding a pooled sensitivity of 48.6% (95% CI 37.1-60.2%) and a pooled specificity of 93.2% (95% CI 73.3-98.5%). CONCLUSION: T2 hyperintensity of deep fascia at MRI has high sensitivity and moderate specificity in diagnosing NSTI. Presence of gas at CT has low sensitivity but high specificity. A combination of diagnostic criteria may improve diagnostic performance, but this needs further investigation.