Bacterial pyomyositis: MRI and clinical correlation

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.

Ultrasound-Guided Percutaneous Drainage of Iliopsoas Abscess With Septicemia in an Adolescent: A Case Report and Literature Review

Introduction

Iliopsoas abscess with septicemia in the pediatric population is rare. Early diagnosis and effective management of this emergent disorder remain challenging for clinicians.

Case Presentation

A 14-year-old girl presented with right lateral and posterior hip pain and fever for 7 days before admission. Blood culture was positive for Staphylococcus aureus. Enhanced magnetic resonance imaging revealed abscesses located in the right iliopsoas muscle and on the surface deep to the fascia of the right sacroiliac joint that were 6.8 cm × 6.2 cm × 5.7 cm and 3.7 cm × 3.5 cm × 2.1 cm, respectively. A diagnosis of right iliopsoas abscesses with septicemia was made. The patient received intravenous antibiotics, underwent ultrasound-guided percutaneous catheter drainage, and recovered uneventfully. Medical literature regarding this issue published in the English language during the last two decades was reviewed.

Discussion

Primary synchronous psoas and iliacus muscle abscesses are rare and emergent disorders in the pediatric age group. The diagnosis is generally delayed owing to the deep anatomic location and nonspecific signs and symptoms. A comprehensive medical history, meticulous physical examination, and judicious use of imaging studies could establish a timely and accurate diagnosis. Surgeons should be aware of the occurrence of multiple abscesses. Prompt and adequate antibiotic therapy accompanied by a mini-invasive approach, such as ultrasound-guided, laparoscopic, or video-retroperitoneoscopic drainage of the infectious focus, if indicated and feasible, is important to achieve a good outcome in the management of iliopsoas abscess.

Pelvic Pyomyositis in Childhood: Clinical and Radiological Findings in a Tertiary Pediatric Center

Pyomyositis (PM) is an infrequent but increasing bacterial infection of the skeletal muscle, with muscles of the pelvis and thigh frequently involved. The diagnosis is often challenging, especially when a deep muscle is affected. We present a single-center pediatric cohort affected by pelvic PM. A retrospective analysis was performed, including children admitted to Meyer Children’s Hospital between 2010 and 2020. Demographic, anamnestic, clinical, laboratory, radiological and management data were collected. Forty-seven patients (range 8 days–16.5 years, 66% males) were selected. Pain (64%), functional limitations (40%) and fever (38%) were the most common presenting symptoms; 11% developed sepsis. The median time to reach the diagnosis was 5 days (IQR 3–9). Staphylococcus aureus was the most common organism (30%), Methicillin-Resistant S aureus (MRSA) in 14%. PM was associated with osteomyelitis (17%), arthritis (19%) or both (45%). The infection was multifocal in 87% of children and determined abscesses in 44% (40% multiple). Pelvic MRI scan, including diffusion-weighted imaging (DWI), always showed abnormalities when performed. Clinical and laboratory findings in pelvic PM are unspecific, especially in infancy. Nevertheless, the infection may be severe, and the suspicion should be higher. MRI is the most useful radiological technique, and DWI sequence could reveal insidious infections.

Factors associated with pyomyositis: A systematic review and meta-analysis

OBJECTIVES

Pyomyositis, an acute bacterial infection of skeletal muscle usually resulting in abscess formation, is well recognised in tropical regions where it can account for up to 4% of adult surgical admissions. It is increasingly being reported from high-income temperate countries. Pyomyositis occurs across all ages and in both sexes. Mortality ranges from 1% to 23%. Many risk factors have been suggested. We aimed to identify factors associated with pyomyositis.

METHODS

We undertook a systematic review and meta-analysis, using PubMed, EMBASE, Scopus and the Cochran Library and hand-searching published papers. The random-effects model meta-analysis was used to calculate pooled estimated odd ratios with the corresponding 95% confidence interval.

RESULTS

All studies in the systematic review (n = 25) and the meta-analysis (n = 12) were hospital-based. Seven only included children. Relatively few studies have been published in the last decade, the majority of which are from high-income temperate settings. Staphylococcus aureus was the main organism isolated. Males under the age of 20 predominated, and mortality of up to 20% was reported. Factors associated with pyomyositis were HIV infection (OR = 4.82; 95% CI: 1.67-13.92) and fulfilling an AIDS surveillance definition (OR = 6.08; 95% CI: 2.79-13.23).

CONCLUSIONS

Our meta-analysis indicated significant associations between pyomyositis infection and HIV/AIDS. Major gaps in our understanding of the epidemiology, pathogenesis, clinical presentation, and outcome remain, highlighting the need for further research and more systematic studies. Pyomyositis merits consideration as a neglected tropical disease.

Pseudomonas aeruginosa Pyomyositis in a Child With Acute Lymphoblastic Leukemia: A Case Report and Review of Literature

BACKGROUND

We report the case of an 11-year-old girl with a recent diagnosis of common B-cell acute lymphoblastic leukemia who presented with Pseudomonas aeruginosa pyomyositis of the left lower limb during severe neutropenia associated with the induction phase of chemotherapy.

OBSERVATIONS

Presenting signs included fever, leg pain, and refusal to walk. Popliteal knee ultrasonography was unremarkable, whereas magnetic resonance imaging showed 2 intramuscular fluid collections requiring surgically drainage.

CONCLUSION

A review of medical literature showed that pyomyositis is an infrequent complication in children with hematological malignancies, and most cases are due to Staphylococcus aureus, whereas Pseudomonas aeruginosa appears to be rarely involved.

A toddler with a persisting limp after a minor trauma

A 3-year-old toddler was admitted for a 5-day history of worsening painful limping on his left leg. History was remarkable only for a minor trauma 2 days before the onset of symptoms; the boy fell on his buttocks but was walking normally in the following days. No fever was reported. Pain was also present at night, with no response to oral ibuprofen.On physical examination, the patient refused to stand on his left leg, palpation of the left buttock evoked pain, and exorotation and abduction of the left hip were only moderately limited, without local signs of inflammation such as redness, swelling or skin warming. Blood tests showed elevated erythrocyte sedimentation rate (ESR) (98 mm/hour, normal value <20 mm/hour) with normal C reactive protein (CRP) level (0.5 mg/dL, normal value <0.5 mg/dL). His white cell count was 12 110 x 109/L, haemoglobin was 127 g/L and PLT was 430 x 109/L. Creatine kinase values were within the normal range.An X-ray of the pelvis was unremarkable. An ultrasound of the left hip showed a 2 mm articular effusion.

Pyomyositis and Infectious Myositis: A Comprehensive, Single-Center Retrospective Study

Background

Pyomyositis is a bacterial infection of skeletal muscle that classically leads to abscess formation. A related, but distinct, entity is infectious myositis. The epidemiology of these infections has changed in recent years.

Methods

To better characterize both pyomyositis and infectious myositis, we conducted a retrospective study at our tertiary care institution. We identified 43 cases of pyomyositis and 18 cases of infectious myositis treated between January 2012 and May 2020.

Results

The mean age of patients was 48 years, and 66% were male. Diabetes mellitus affected one third of patients, and 16% had other immunocompromising comorbidities. Staphylococcal species accounted for 46% of all infections, and common symptoms included muscle pain (95%) and subjective fever (49%). Altered mental status was a presenting symptom in 16% of cases. Approximately half of all patients received >1 class of antibiotic, and the median length of antimicrobial therapy was 18 days. Open and percutaneous drainage procedures figured prominently in the management of these infections, with 28% of patients requiring multiple procedures. Pathology specimens were available for 12 of 61 cases. Overall, the treatment success rate was 84%.

Conclusions

Gram-positive bacteria accounted for most infections at our institution, and management commonly involved open or percutaneous drainage procedures. Future studies that prospectively evaluate treatment strategies for pyomyositis and infectious myositis are warranted.

MRI nomenclature for musculoskeletal infection

The Society of Skeletal Radiology (SSR) Practice Guidelines and Technical Standards Committee identified musculoskeletal infection as a White Paper topic, and selected a Committee, tasked with developing a consensus on nomenclature for MRI of musculoskeletal infection outside the spine. The objective of the White Paper was to critically assess the literature and propose standardized terminology for imaging findings of infection on MRI, in order to improve both communication with clinical colleagues and patient care.A definition was proposed for each term; debate followed, and the committee reached consensus. Potential controversies were raised, with formulated recommendations. The committee arrived at consensus definitions for cellulitis, soft tissue abscess, and necrotizing infection, while discouraging the nonspecific term phlegmon. For bone infection, the term osteitis is not useful; the panel recommends using terms that describe the likelihood of osteomyelitis in cases where definitive signal changes are lacking. The work was presented virtually to SSR members, who had the opportunity for review and modification prior to submission for publication.

Use of Magnetic Resonance Imaging for Orthopedic Trauma and Infection in the Emergency Department

Conditions affecting the musculoskeletal system constitute a significant portion of medical emergencies in the United States, with traumatic injury and infection being two of the most common etiologies. Although physical examination and plain radiographs are often sufficient to guide diagnosis and treatment, there are myriad traumatic and infectious pathologies that are commonly missed or simply not detectable on plain radiographs. Advanced imaging is subsequently warranted for additional workup.Magnetic resonance imaging (MRI) has become an increasingly used imaging modality for musculoskeletal complaints in the emergency department due to its superior visualization of soft tissues, focal edematous changes, and occult osseous insults often not visible on plain radiographs. Although multiple studies have evaluated its utility in the workup of emergency musculoskeletal complaints, there remains a dearth of literature examining the use of MRI for certain occult diagnoses.Radiologists, emergency clinicians, and orthopedic surgeons must be knowledgeable of the indications for MRI in the emergency setting, as delayed diagnosis may contribute to increased morbidity and possibly mortality. This review summarizes the use of MRI in diagnoses relating to trauma or infection among patients presenting to the emergency department with a musculoskeletal complaint.

Discrimination between tuberculous and bacterial pyomyositis in magnetic resonance features

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Discriminating imaging features between bacterial and tuberculous pyomyositis.

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T2 high signal intensity at abscess wall can predict for bacterial pyomyositis.

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Abscess wall character on imaging of bacterial muscle infection.

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Magnetic resonance imaging between bacterial and tuberculous muscle infection.

Purpose

The purpose of this study was to assess the differences of magnetic resonance features between tuberculous and bacterial pyomyositis.

Method

This is a retrospective study of patients with bacterial and tuberculous pyomyositis. We excluded patients with pyomyositis caused by actinomycosis, non-tuberculous mycobacterium, fungi, unknown of causative organism, or inadequate imaging for analysis. Magnetic resonance imaging was independently reviewed by two radiologists.

Results

Of the 136 pyomyositis patients, 71 (52.2 %) patients had bacterial pyomyositis while 65 (47.8 %) patients had tuberculous pyomyositis. Seventy-seven patients (56.6 %) had intramuscular abscess. On multivariable analysis, bacterial pyomyositis was associated with diabetes mellitus (odds ratio [OR] 3.17, 95 % confidence interval [CI] 1.30–8.24) and bone marrow involvement (OR 5.02, 95 % CI 1.21–34.4). Spinal involvement had a significantly lower likelihood of bacterial pyomyositis (OR 0.25, 95 %CI 0.11–0.54). In patients with intramuscular abscess, diabetes mellitus and hyperintense on T2-weighted images at the abscess wall had a significantly higher likelihood of bacterial pyomyositis (OR 5.21, 95 %CI 1.33–25.42 and OR 5.34, 95 %CI 1.36–24.71, respectively), whereas spinal involvement had a significantly lower likelihood of bacterial pyomyositis (OR 0.09, 95 %CI 0.02–0.30).

Conclusions

Magnetic resonance imaging has modest accuracy for differentiation of tuberculous and bacterial pyomyositis. Diabetes mellitus and extraspinal pyomyositis were the predictors of bacterial pyomyositis. Presence of T2 hyperintense wall of intramuscular abscess was also the predictor of bacterial pyomyositis.

Uncommon primary Group A streptococcal erector spinae pyomyositis diagnosed as muscle strain in a fit young male

Acute lower back pain in a fit healthy male with recent strenuous physical activity is often attributed to muscle strain. We report a rare case of erector spinae pyomyositis developing in a young and otherwise healthy young adult male that was almost misdiagnosed as muscle strain. Despite admission and close monitoring, diagnosis was only confirmed on a magnetic resonance imaging of the spine later during the hospital stay. Early diagnosis in this case allowed successful treatment with intravenous antibiotics alone, without requiring further surgical drainage or development of further neurological sequelae, common in later stages of erector spinae pyomyositis.

Fever and Hip Pain: Not Always Due to a Septic Hip

Hip pain in febrile children always raises concern for septic arthritis. Pyomyositis is a rare cause of hip pain. Because it involves muscles around the joint, it may have a similar presentation as a septic hip. This entity therefore has the potential for posing a diagnostic dilemma when physicians face a limping child with fever. We report a child who presented with fever and hip pain and has pyomyositis of the obturator internus muscle. This case underscores the need to consider the possibility of alternative etiologies in a limping child.

Sonographic appearance of pyomyositis of the sternocleidomastoid muscle: A case report

Pyomyositis in the neck has rarely been described. We present the sonographic findings in a case of pyomyositis of the sternocleidomastoid muscle. A 62-year-old man with poorly controlled diabetes presented with an induration of the neck and fever. On gray-scale sonography, a part of the sternocleidomastoid muscle appeared swollen and contained irregularly shaped hypoechoic areas. Power Doppler imaging showed increased vascularity in the muscle. Sonographic-guided aspiration confirmed abscesses in the sternocleidomastoid muscle. Surgical drainage was successfully performed along with antibiotic treatment. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:520-523, 2017.

Magnetic resonance imaging of painful swollen legs in the emergency department: a pictorial essay

Patients presenting with a painful swollen leg are not infrequently encountered at the emergency department and can pose a diagnostic dilemma for attending physicians. The potential causes of leg pain and swelling include trauma, infection, inflammation, and neurogenic, vascular, and iatrogenic conditions; with magnetic resonance imaging (MRI) being an important tool in evaluation. We describe the MRI features of various conditions causing painful swollen legs. We also discuss the differential diagnosis and the useful clinical and laboratory findings that radiologists should be aware of, in order to arrive at an accurate diagnosis.

Shoulder Pain after Fall, Septic Shock, and Pyomyositis Associated with Breast Cancer Chemotherapy and Lymphedema

Background

As a symptom of pyomyositis, sepsis usually follows local inflammation signs. Here, we report pyomyositis with lymphedema of upper extremity in which septic shock and poor local findings initially presented during chemotherapy for breast cancer.

Case Report

An 80-year-old woman presented with chronic right shoulder pain during chemotherapy for the recurrent disease. She had a history of postmastectomy lymphedema, diabetes mellitus, and repeated hyaluronic acid injections to the shoulder joint. The pain suddenly worsened with septic shock and no apparent local signs. Magnetic resonance imaging revealed myonecrosis, and no pus was yielded by ultrasound-guided needle aspiration. After 2 weeks of recovery by conservative medical management, surgical drainage was performed. Late formulated massive intramuscular pus showed severe neutrophil infiltration and myonecrosis.

Conclusion

Pyomyositis can develop into septic shock with poor local signs. Myelosuppression after chemotherapy can cause myonecrosis without macroabscess, and magnetic resonance imaging was useful for the diagnosis of this condition. When unspecified local pain appears during cancer chemotherapy we should consider this disease, too.

Pyomyositis Causing Temporary Quadriparesis During Induction Therapy for Acute Lymphoblastic Leukemia: Case Report and Review of the Literature

Pyomyositis (PM) is a purulent infection of skeletal muscle. It is often associated with immunosuppression in temperate climates. Herein, we report a case of PM causing temporary quadriparesis in a 14-year-old girl undergoing induction therapy for acute lymphoblastic leukemia and we review the reported pediatric cases associated with induction therapy for hematologic malignancies. Early symptoms of PM can be mistaken for the side effects of chemotherapeutic agents. Greater awareness of the clinical picture of PM will aid in early diagnosis and treatment. With appropriate medical therapy and timely abscess drainage, morbidity and mortality is greatly reduced.

Nontropical pyomyositis complicated with spinal epidural abscess in a previously healthy child

Background:

Pyomyositis (PM), a rare pyogenic infection that involves skeletal muscles, if not immediately diagnosed, can be fatal. Most notably, this results in spinal epidural abscess (SEA) in typically unhealthy individuals.

Case description:

We present a very rare nontropical PM complicated with SEA in a previously healthy child revealed by Magnetic resonance imaging (MRI). Our patient recovered without complications 5 years after abscess drainage and antibiotics.

Conclusion:

PM remains a challenge to clinicians and should be considered in the differential diagnosis of musculoskeletal pain. MRI is the investigation of choice of spinal infection and should be undertaken at an early stage.

[Primary tuberculous pyomyositis in an immunocompetent patient: report of a case]

L'atteinte du muscle strié au cours de la tuberculose chez un sujet immunodéprimé ou à partir de l'extension d'un foyer ostéo-articulaire de voisinage est rare mais bien connue. Toutefois, l'atteinte primitive est exceptionnelle ainsi que celle chez un sujet immunocompétent. L'imagerie par résonnance magnétique (IRM) est d'un grand apport pour le diagnostic avec une excellente sensibilité. Nous rapportons un cas de pyomyosite tuberculeuse primitive du mollet chez une patiente non immunodéprimé tout en précisant l'apport de l'IRM.

Magnetic resonance imaging of muscle disease: a pattern-based approach

Magnetic resonance imaging (MRI) is a powerful tool to assess the severity, distribution, and progression of muscle injury and disease. However, a muscle's response to a pathological insult is limited to only a few patterns on MRI, and findings can be nonspecific. A pattern-based approach is therefore essential to correctly interpret MR studies of abnormal muscle. In this article we review the anatomy, function, and normal MRI appearance of skeletal muscle. We present a classification scheme that categorizes abnormal MR appearances of muscle into 4 main pattern descriptors: (1) distribution; (2) change in size and shape; (3) T1 signal; and (4) T2 signal. Each category is further subdivided into the various patterns seen on MRI. Such an approach allows one to systematically assess abnormal findings on muscle MRI studies and ascertain clues to the diagnosis or differential diagnosis, particularly when findings are correlated with the clinical context.

Early presentation of heterotopic ossification mimicking pyomyositis - two case reports -

Early diagnosis and treatment of heterotopic ossification (HO) is essential to the prevention of complications. It is difficult to diagnose HO in its initial phase because non-specific clinical manifestations, laboratory findings and imaging findings of immature HO may mimic other diseases such as cellulitis, osteomyelitis, thrombophlebitis, deep vein thrombosis and local infection with abscess. We experienced two cases of HO, which were misdiagnosed as pyomyositis at first by clinical signs and MRI findings indicating the deep infection; the extensive intramuscular ossification appeared later on. We observed an increase of C-reactive protein and creatine kinase followed by the elevation of alkaline phosphatase with abnormal triphasic bone scan. The trajectory of these biomarkers was analyzed to get more insight into the early stages of HO along with the imaging findings. Although our cases cannot be generalized as typical of immature HO, they clearly demonstrate that the change of specific biomarkers with a careful history taking and physical examination should be noted to detect HO as early as possible while avoiding confusion with other mimicking conditions.

Staphylococcus aureus pyomyositis compared with non-Staphylococcus aureus pyomyositis

OBJECTIVES

Pyomyositis is an acute bacterial infection of skeletal muscle not arising from contiguous infection. It is often hematogenous in origin and typically associated with abscess formation. Our objective was to determine if there were any differences in the clinical presentation of disease between Staphylococcus aureus (SA) and non-Staphylococcus aureus pyomyositis. We also sought to determine if methicillin-resistant SA (MRSA) occurred more frequently during the final years of the study period.

METHODS

A retrospective chart review study at three institutions in two cities.

RESULTS

Sixty cases of pyomyositis were identified between 1990 and 2010. Twenty-nine patients were infected with SA while 31 had other bacterial etiologies or were culture negative. Those with a traumatic event prior to the onset of infection were more likely to have a SA infection while SA infected patients were younger. Our first documented case of MRSA occurred in 2005, but the frequency of MRSA infection remained static over the following five years.

CONCLUSIONS

Pyomyositis is an emerging infection that is underappreciated by many physicians. While MRSA has emerged as the foremost cause of SA infections in a majority of clinical conditions, in this series most patients still had methicillin-sensitive SA as their cause of pyomyositis. In light of the severity of pyomyositis and the potential for bacteremia (either as a source or complication of the infection), empiric SA therapy should be initiated in all patients until the culture results are available.

Pyomyositis

Poorly controlled diabetes is associated with an increased risk of infectious complications. With the increasing prevalence of diabetes, many more people are being looked after in primary care. We describe a case of pyomyositis, a potentially severe but uncommon complication of poorly controlled diabetes that was not recognised in the community. Clinicians looking after people with diabetes need to be aware that prolonged, unexplained symptoms need specialist assessment.

Spontaneous bacterial seeding of a biceps hematoma

A 19-year-old male construction worker presented with an injury to his left upper arm after lifting a heavy pipe. He reported an acute onset of sharp pain followed by swelling, warmth, and weakness with elbow flexion. The diagnosis of a distal biceps tendon rupture was made and elective repair was scheduled. Seventy-two hours later, the patient presented with a spontaneous draining wound on his anterior distal humerus. The wound was draining thick purulent material. The patient underwent surgery for irrigation and debridement of his abscess. Nearly 500 cc of hematoma and purulent fluid were evacuated. A large tear of both the biceps and brachialis muscle bellies were found. Cultures were obtained that revealed the infecting organism to be Streptococcus intermedius. Human immunodeficiency virus and hepatitis-C virus testing were negative, and no history, signs, or symptoms of any cause of underlying immunodeficiency were detected. No signs or history of drug use were present. He was discharged home on culture-specific oral antibiotics. At 4-month postoperative follow-up, the patient reported no pain or limitations. He has returned to full duty at his job. Elbow range of motion was measured from 7° to 150° of flexion. Strength of elbow flexion and extension was symmetric to the uninjured side. Pronation and supination of the forearm was symmetric on both sides. He has been released from scheduled follow-up and will be seen again on an as-needed basis.

Clinical impact of gadolinium in the MRI diagnosis of musculoskeletal infection in children

BACKGROUND

The incremental value of gadolinium in the diagnosis of musculoskeletal infection by MRI is controversial.

OBJECTIVE

To compare diagnostic utility of noncontrast with contrast MRI in the evaluation of pediatric musculoskeletal infections.

MATERIALS AND METHODS

We reviewed 90 gadolinium-enhanced MRIs in children with suspected musculoskeletal infection. Noncontrast and contrast MRI scans were evaluated to determine sensitivity and specificity in the diagnosis of musculoskeletal infection and identification of abscesses.

RESULTS

Pre- and post-contrast diagnosis of osteomyelitis sensitivity was 89% and 91% (P = 1.00) and specificity was 96% and 96% (P = 1.00), respectively; septic arthritis sensitivity was 50% and 67% (P = 1.00) and specificity was 98% and 98% (P = 1.00), respectively; cellulitis/myositis sensitivity was 100% and 100% (P = 1.00) and specificity was 84% and 88% (P = 0.59), respectively; abscess for the total group was 22 (24.4%) and 42 (46.6%), respectively (P < 0.0001). Abscesses identified only on contrast sequences led to intervention in eight additional children. No child with a final diagnosis of infection had a normal pre-contrast study.

CONCLUSION

Intravenous gadolinium should not be routinely administered in the imaging work-up of nonspinal musculoskeletal infections, particularly when pre-contrast images are normal. However, gadolinium contrast significantly increases the detection of abscesses, particularly small ones that might not require surgical intervention.

[Pyomyositis of adductor muscles caused by Escherichia coli in an immunocompetent patient living in a temperate climate]

Pyomyositis is a primitive infection of the skeletal muscle usually caused by Staphylococcus aureus in tropical areas, and associated with immunodeficiency. We report a 49-year-old immunocompetent woman, living in a temperate climate presenting with a pyomyositis of adductor muscles caused by Escherichia coli. Diagnosis was obtained with magnetic resonance imaging (MRI). Disease course was uneventful after surgical debridement and antibiotics. This case report highlights the usefulness of MRI in the diagnosis of pyomyositis.

MR imaging evaluation of disorders of the chest wall

Chest wall lesions constitute a diverse group of thoracic diseases, including those of soft tissue and osseous origin. MR imaging, with its superior tissue-resolving capability and multiplanar image acquisition, is an important tool for assessing chest wall lesions. In this article, the authors review common and uncommon diseases of the chest wall, with an emphasis on the MR imaging characteristics of these diseases. Among the diseases they discuss are diseases of the soft tissue including lipoma, hibernoma, liposarcoma, hemangioma, and lymphoma. They also examine diseases of the osseous thorax, including benign osseous tumors, fibrous dysplasia, and aneurysmal bone cyst. In addition, they discuss such malignant osseous tumors as osteosarcoma and Ewing's sarcoma.

Increased oxacillin resistance in thigh pyomyositis in diabetic patients

Thigh abscesses due to pyomyositis are uncommon. To guide empiric antibiotic therapy in diabetics we determined the rate of such infections due to oxacillin-resistant Staphylococcus aureus and Gram-negative organism infections, and whether the occurrence of oxacillin-resistant pathogens increased during the study period. We retrospectively reviewed 39 adult patients with diabetes mellitus treated for a deep thigh abscess. There were 29 men and 10 women; their mean age was 45 years. Comorbidities were present in 15 patients. S. aureus was the most common pathogen, present in 82% (32/39) of our patients. Gram-negative organisms were cultured in 14% (6/39) of patients and anaerobes in 10% (4/39). The infection was polymicrobial in 12 of 39 patients (31%). Oxacillin-resistant S. aureus comprised 25% (8/32) of infections due to S. aureus. Oxacillin-resistance increased during the last 3 years of this study from one of 18 S. aureus isolates from 1994 to 2004 to seven of 14 isolates from 2004 to 2006. In diabetic patients with thigh pyomyositis, empiric antibiotic therapy should provide broad spectrum coverage for oxacillin-resistant S. aureus, Gram-negative, as well as anaerobic organisms.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Primary erector spinae pyomyositis causing an epidural abscess: case report and literature review

BACKGROUND CONTEXT

Primary pyomyositis (PM) is a rare bacterial infection of skeletal muscle usually restricted to tropical zones. Typically caused by Staphylococcus aureus, primary staphylococcal PM associated with an epidural abscess has not been reported before.

PURPOSE

We present the first case of staphylococcal PM associated with an epidural abscess.

STUDY DESIGN

Case report.

PATIENT SAMPLE

A 56-year-old woman.

OUTCOME MEASURES

Clinical follow-up at 9 months.

METHODS

This 56-year-old woman presented with a sudden onset of left lumbar back pain and sciatica without prior illness. She was pyrexial on admission, with elevated inflammatory markers but with no obvious systemic source of sepsis.

RESULTS

Spinal magnetic resonance imaging and subsequent surgery revealed an erector spinae abscess causing an epidural abscess via the left L4/5 intervertebral foramen. Both back pain and sciatica were immediately improved postoperatively. Culture revealed S aureus as the sole organism sensitive to flucloxacillin. Intravenous therapy was converted to oral after 12 days once the erythrocyte sedimentation rate had normalized and she was asymptomatic. She remains asymptomatic and without clinical signs at the 9-month follow-up.

CONCLUSION

Spinal infection must always be considered when back pain and sciatica are associated with clinical signs of sepsis. We present the first case of staphylococcal PM associated with an epidural abscess.

Pyomyositis associated with hematological malignancy: case report and review of the literature

Pyomyositis occurs most commonly in patients with various immunosuppressive diseases. However, the association of pyomyositis with an underlying hematological malignancy has not been reviewed. We present herein a relevant case and also review the available literature regarding the association of non-tropical pyomyositis and hematological malignancies. The case patient, a 46-year old female, had non-tropical pyomyositis of the iliopsoas and obturator muscles due to Staphylococcus aureus and underlying Hodgkin's disease. Forty-four patients with pyomyositis and an associated hematological malignant disease have been reported in the literature. The most common types of hematological oncology diseases found were acute lymphocytic leukemia (present in 11/44 patients (25%)) and multiple myeloma (7/44 patients (15.9%)). Staphylococcus aureus was the most common cause of pyomyositis (26 out of 44 patients (59.1%)). The muscles of the thigh were most commonly affected (18/44 patients (40.9%)). Medical therapy with antibiotics and surgical drainage were employed in 25/44 (56.8%) of the patients. Thirty out of 44 (68.2%) of the patients had a successful outcome. Death occurred in 5/44 (11.4%) patients. In cases of pyomyositis, the physician should consider an underlying hematological malignancy.

Rhabdomyolysis: magnetic resonance imaging and computed tomography findings

OBJECTIVE

Our purpose was to describe the magnetic resonance (MR) imaging and computed tomography (CT) findings in patients with rhabdomyolysis.

METHODS

The medical records and imaging studies of 10 patients (5 males, 5 females; age range, 14-60 years; mean age, 28.3 years) with rhabdomyolysis were retrospectively reviewed. Magnetic resonance imaging was available in 9 patients and CT in 2 patients.

RESULTS

Two distinct imaging types of rhabdomyolysis were observed. For type 1 rhabdomyolysis (n = 2), the affected muscles revealed homogeneously isointense to hyperintense on T1-weighted, homogeneously hyperintense on T2-weighted and short-tau inversion recovery (STIR) images, and homogeneously enhanced on contrast-enhanced MR images. For type 2 rhabdomyolysis (n = 8), the affected muscles revealed homogeneously or heterogeneously isointense to hyperintense on T1-weighted images, heterogeneously hyperintense on T2-weighted and STIR images, heterogeneously hypodense on CT images, and rim enhanced on contrast-enhanced MR and CT images with the presence of a specific presentation, named as the "stipple sign."

CONCLUSIONS

Rhabdomyolysis is a clinical and biochemical syndrome comprising 2 distinct imaging types. Homogeneous signal changes and enhancement in the affected muscles advocate type 1 rhabdomyolysis. The stipple sign is helpful in demonstrating the areas of myonecrosis in type 2 rhabdomyolysis and, together with clinical and laboratory presentations, in reaching the correct diagnosis.

A pediatric case of pyomyositis presenting with septic pulmonary emboli

Pyomyositis is a suppurative infection of skeletal muscle most commonly caused by Staphylococcus aureus. It is mainly encountered in children and immunocompromised. Eight year old previously healthy girl presented with confusion, fever and swelling of the right knee two days after a trauma. Abdominal ultrasonography and computerized tomography taken upon development of hematemesis revealed no pathology in the abdomen, but potential bleeding sites in lung sections. Thorax CT images were interpreted in favor of septic pulmonary emboli due to the presence of peripheral nodular consolidation areas with central cavitation, mostly pathchy in medial areas. S. aureus was isolated in the blood culture. At the end of third week of hospitalization, gadolinium enhanced contrast MRI of right extremity was taken to evaluate right extremity swelling and revealed abscess formation as expected in the clinical progress of pyomyositis. Pyomyositis and septic pulmonary emboli are a rare association. This case demonstrates that the high index of suspicion in pediatric cases with muscle findings and septic pulmonary findings and early institution of therapy may improve the prognosis.

MR imaging findings of pyogenic bacterial myositis (pyomyositis) in patients with local muscle trauma: illustrative cases

Pyogenic myositis (pyomyositis) represents a bacterial infection of muscle, usually caused by Staphylococcus aureus that is endemic in tropical regions. Pyomyositis commonly affects patients who are immunocompromised or who have underlying chronic disorders. Lower extremity localization of infection is typical. The most common pattern of disease, however, appears to be a solitary abscess in the quadriceps musculature. Delay in accurate diagnosis is frequent and clinical deterioration can be precipitous. In view of the high associated morbidity, early imaging to detect, localize, and define disease extent is important. Magnetic resonance imaging (MRI) plays a key role in the definitive diagnosis of pyomyositis. This article provides a pictorial illustration of the spectrum of MRI findings associated with pyogenic myositis.

Heterotopic ossification of the knee joint in intensive care unit patients: early diagnosis with magnetic resonance imaging

INTRODUCTION

Heterotopic ossification (HO) is the formation of bone in soft tissues. The purpose of the present study was to evaluate the magnetic resonance imaging (MRI) findings on clinical suspicion of HO in the knee joint of patients hospitalised in the intensive care unit (ICU).

METHODS

This was a case series of 11 patients requiring prolonged ventilation in the ICU who had the following diagnoses: head trauma (nine), necrotising pancreatitis (one), and fat embolism (one). On clinical suspicion of HO, x-rays and MRI of the knee joint were performed. Follow-up x-rays and MRI were also performed.

RESULTS

First x-rays were negative, whereas MRI (20.2 +/- 6.6 days after admission) showed joint effusion and in fast spin-echo short time inversion-recovery (STIR) images a 'lacy pattern' of the muscles vastus lateralis and medialis. The innermost part of the vastus medialis exhibited homogeneous high signal. Contrast-enhanced fat-suppressed T1-weighted images also showed a 'lacy pattern.' On follow-up (41.4 +/- 6.6 days after admission), STIR and contrast-enhanced T1-weighted images depicted heterogeneous high signal and heterogeneous enhancement, respectively, at the innermost part of the vastus medialis, whereas x-rays revealed a calcified mass in the same position. Overall, positive MRI findings appeared simultaneously with clinical signs (1.4 +/- 1.2 days following clinical diagnosis) whereas x-ray diagnosis was evident at 23 +/- 4.3 days (p = 0.002).

CONCLUSION

MRI of the knee performed on clinical suspicion shows a distinct imaging pattern confirming the diagnosis of HO earlier than other methods. MRI diagnosis may have implications for early intervention in the development of HO.

Acute pyomyositis of the pelvis: the spectrum of clinical presentations and MR findings

BACKGROUND

Acute pelvic pyomyositis is uncommon in non-tropical areas.

OBJECTIVE

To summarize the clinical and MR findings in children with acute pelvic pyomyositis.

MATERIALS AND METHODS

We retrospectively identified 20 children (mean age 9.4 years) who were evaluated by MR and diagnosed with acute pelvis pyomyositis during the time period between January 2002 and June 2005. We reviewed clinical, laboratory, and imaging findings.

RESULTS

Fifteen of the 20 children had secondary pyomyositis associated with osteomyelitis (n=13), septic hip (n=4) or sacroiliitis (n=4); all were previously healthy except for one child with leukemia. Seven of the children with secondary pyomyositis underwent bone scintigraphy; three (43%) did not show pelvic abnormalities. Staphylococcus aureus was cultured in 13 of the 15 (87%) children. Five of the 20 children had primary pyomyositis. Three had underlying disease and two others were engaged in vigorous physical activity. Bone scintigraphies (n=2) were negative. Cultures were positive for S. aureus in three of the five (60%) children.

CONCLUSION

Septic hip should be the first diagnostic consideration in children with fever and acute hip pain. Pyomyositis should be considered if arthrocentesis is negative or there is clinical suspicion of infection outside the hip joint. MR is the preferred imaging modality for evaluating foci of pyomyositis, muscle abscesses, and additional foci of infection within the pelvis.

[Paravertebral pyomyositis in childhood following closed injury]

Pyomyositis is an acute bacterial infection that affects striated muscle and is generally accompanied by the formation of an abscess. In most cases, the microorganism involved is Staphylococcus aureus. Clinical findings are characterized by pain, swelling and muscular edema, together with variable general symptoms. Complications include arthritis, osteomyelitis and even septic shock with a mortality of 1.8%. We report the case of an 8-year-old boy who sustained a closed lumbar injury on banging his shoulder while he was playing on a trampoline and who developed paravertebral pyomyositis complicated by sepsis. S. aureus was isolated in the blood culture. The boy subsequently developed a perivertebral abscess and finally contiguous osteomyelitis in the L3 spinous process. The patient received treatment with vancomycin and metronidazole for 6 weeks followed by cloxacillin therapy for 2 weeks (a total of 8 weeks of intravenous antibiotic therapy). Physical examination 3 months after discharge revealed no abnormalities. The possibility of pyomyositis should be borne in mind, especially in children with fever, localized muscular pain and a history of accidental or sports injuries. Early diagnosis and treatment are important to reduce the risk of possibly fatal complications.

Isolated obturator externus muscle abscess presenting as hip pain

The case of a 20-year-old diabetic male with 2 weeks of hip pain, diagnosed with an isolated obturator externus muscle abscess, is reported. Pyomyositis, or abscess formation deep within a large striated muscle, is a rare but potentially life-threatening disease.