Magnetic resonance imaging of pyomyositis in 43 cases

doi:10.1016/S0720-048X(99)00108-4

European Journal of Radiology

Volume 35, Issue 1, July 2000, Pages 59-64

https://doi.org/10.1016/S0720-048X(99)00108-4 Get rights and content

Abstract

Purpose: To describe the magnetic resonance imaging (MRI) findings in pyomyositis. Methods and materials: Forty-three patients with proven muscle infection (30 males, 13 females) ranging in age from 14 to 86 years (mean 42 years) were studied with MRI. The initial clinical diagnose were soft tissue infection (n=27), neoplasm (n=12), thrombophlebitis (n=3), and lymphedema (n=1). Spin-echo T1- and T2-weighted images were obtained in all cases and STIR sequence in 6. Spin-echo T1-weighted images after Gd-DTPA injection were obtained in 16 cases. The signal intensity findings, the extent of the abnormalities in the soft tissue (muscle, fascial and subcutaneous involvement), the presence of fluid collections, and the involvement of neighbouring bone and joint were reviewed retrospectively. Results: A hyperintense signal on T2-weighted and STIR images were detected in all patients. Fluid collections were seen in 21 cases as localized areas of hypointensity on the T1-weighted images, and highly hyperintense areas on the T2-weighted images. In four patients a rim of high signal intensity was seen around the fluid collection on the T1-weighted images. On contrast-enhanced T1-weighted images there was diffuse enhancement in the patients without fluid collections that was heterogeneous in seven and homogeneous in two. After Gd-DTPA all fluid collections showed a central area without enhancement and a well-defined enhancing peripheral rim. Involvement of adjacent structures included subcutaneous tissue (n=25), bone marrow (n=14), fascial planes (n=15) and joints (n=11). Conclusion: MRI is useful in the assessment of pyomyositis and in determining the location and extension. A hyperintense rim on unenhanced T1-weighted images and peripheral enhancement after Gd-DTPA are useful for identifying the number, size, and location of soft-tissue abscesses.

Introduction

Pyomyositis is a primary infection of skeletal muscles, endemic in tropical climates, but rare elsewhere. It presents as an enlarging soft tissue mass associated with pain. Usually, there are no skin changes and the diagnosis may be difficult clinically, because pyomyositis arises deep in the muscle [1], [2], [3]. MRI has become the technique of choice for diagnosis of soft-tissue masses [2]. However, although specific tissue diagnosis is often impossible, characteristic findings have been described for muscle abscess [1], [3], [4], [5]. Accurate assessment of the location and the extent of soft tissue infection is essential for proper treatment, which may include antibiotics, drainage and surgical debridement. Several case reports and a few series have analyzed the role of magnetic resonance imaging (MRI) in detecting soft tissue infection and fluid collections [1], [3], [4], [6]. We reviewed the MRI in 43 patients with proven pyomyositis to identify those characteristics that might be useful in diagnosis.

Section snippets

Material and methods

We retrospectively reviewed the MRI and clinical findings in 43 patients (30 men and 13 women ranging in age from 14 to 86 years) with proven muscle infection over a period of 4 years. Image analysis was performed by two radiologists and any discrepancies were resolved by consensus. The MRI was performed because of clinical suspicion of soft-tissue infection (n=27), soft-tissue tumour (n=12), thrombophlebitis (n=3) or lymphedema (n=1). A review of patient charts showed that the predisposing

Results

The final diagnoses and the location of musculoskeletal infections are summarized in Table 1. The most common cultured organism was Staphylococcus aureus (62.8%) and Mycobacterium tuberculosis (18.6%). The frequency of muscle, fascial planes, subcutaneous tissue, joints and bone marrow involvement is summarized in Table 2. Isolated muscle infection was found in 10 (23.2%) cases, three resulting from M. tuberculosis. The majority of patients (76.8%) had involvement of multiple structures:

Discussion

Pyomyositis is a primary infection of the skeletal muscle. It is endemic in the tropics and, although usually considered rare in temperate regions, it is becoming more common. Outside the tropics, pyogenic myositis tends to occur more frequently in patients with concurrent diseases such as diabetes, human immunodeficiency virus infection, connective tissue disorder or in patients who are immunodeficient for other reasons [1], [3], [7]. S. aureus is the organism responsible in 90% of cases and

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Most agree that radiographs are only useful to rule out osteo-articular complications [186–189] and serve little role in the diagnosis of PIM. Intramuscular collections are preferably diagnosed by ultrasound when they are superficial [172,190,191], and with contrasted computerized tomography (CT) or magnetic resonance imaging (MRI) when deep [71,183,192,193], including cases of the thorax, abdomen or pelvis [80,96]. The CT and MRI scans typically show swelling of muscle(s) affected, with hyperdense/intense area(s) corresponding to intramuscular necrosis or collections [194].
Purulent infectious myositis (PIM), formerly known as tropical pyomyositis, is a pyogenic infection of skeletal muscles. Staphylococcus aureus, a normal human skin inhabitant, is the main pathogen involved, but multiple other microorganisms have been implicated. Although usually a progressive febrile disease with pain in the affected muscle(s), severe, life-threatening forms have been described, especially in immunosuppressed patients and children. PIM may elude early diagnosis given the lack of overlying skin changes. Hence, high index of suspicion followed by imaging modalities (ultrasonography when superficial and computed tomography or magnetic resonance imaging with contrast when deep) help confirm the diagnosis. Treatment requires combination of percutaneous or open surgical drainage along with antimicrobial therapy guided by culture results. The rising incidence of cases due to methicillin-resistant Staphylococcus aureus (MRSA) strains, makes the inclusion of vancomycin be recommended. This paper reviews PIM highlighting its global distribution, causative agents, predisposing factors, management, and potential complications.
Discrimination between tuberculous and bacterial pyomyositis in magnetic resonance features
2020, European Journal of Radiology Open
Citation Excerpt :
In bacterial pyomyositis, earlier stage of blood production, more vascularized granulation tissue and less fibrotic tissue component give rise MR imaging of hyperintense rim on T2-weighted images at the abscess wall. The location of pyomyositis usually involves the larger muscle groups located around the pelvic girdle and lower extremities [1]. Similar to our results, the lower extremities muscles were the one of the most commonly affected location in bacterial pyomyositis.
The purpose of this study was to assess the differences of magnetic resonance features between tuberculous and bacterial pyomyositis.
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.
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).
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.
Percutaneous transgluteal computed tomography-guided aspiration of obturator internus pyomyositis in adolescent athlete: A case report and literature review
2018, Radiology Case Reports
Pyomyositis is an uncommon infection of muscle that is usually managed conservatively, but, can progress to abscess formation requiring open surgical drainage. We present the first reported case of a 14-year-old male with obturator internus pyomyositis requiring computed tomography-guided percutaneous transgluteal drainage for the management of a right obturator internus abscess. We present this case report to provide an alternative to the open surgical management of abscesses from pyomyositis by means of successful computed tomography-guided drainage.
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While enhanced CT was used in five cases to confirm the diagnosis. Recently, if there is any doubt in diagnosis we recommended as other authors the enhanced MRI which is considered the most accurate up to date diagnostic tool for confirming the diagnosis of PM which was used in ten patients in our series [12,13,15,17]. Staphylococcus aureus is the most common causative agent reported in the literature [2–16].
Pyomyositis (PM) is defined as a primary pyogenic infection of the striated skeletal muscle; although it has many dystrophic musculoskeletal complications, it is always misdiagnosed by many orthopedic surgeons.
PM is rare in temperate climates and usually considered to be a tropical disease, until recent times, after globalization, it is possible to occur in the subtropical climate as in our country.
In the present series, the results of 15 children patients with primary pyomyositis have been reviewed. In five out of them, conservative treatment protocol alone which has been by intravenous and oral antibiotics therapy was effective. The remaining ten patients with confirmed abscess formation needed invasive procedures which have been percutaneous US-guided drainage in two patients and an open surgical drainage in the remaining 8 patients.
Conservative treatment was successful in five cases with marked improvement within 3 days, but in the other ten patients who needed surgical treatment, all were effectively treated except three out of them who were complicated as follows; elbow stiffness in one case, hip joint septic arthritis with epiphysitis in the second case and osteomyelitis of the lower femoral end with knee joint septic arthritis in last one.
Both clinical picture and laboratory investigation of PM are not specific and resembled many other differential diagnoses so the proper imaging study is of valuable importance needs to be accurately identified and treated to avoid its delayed complications.
In children complaining of joint pain or muscle aches and septic-appearing, pyomyositis should be considered in the differential diagnosis. MRI is the most valuable tool for diagnosis of PM. Early diagnosis, the use of appropriate antibiotic therapy and complete drainage of the purulent material are important factors for successful treatment that leads to complete resolution of PM.
IV.

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Magnetic resonance imaging of pyomyositis in 43 cases

Abstract

Introduction

Section snippets

Material and methods

Results

Discussion

Comput Med Imaging Graph

Differential diagnosis of bacterial myositis in AIDS: evaluation with MR imaging

Radiology

Musculoskeletal infection: findings on magnetic resonance imaging

Can Assoc Radiol J

Pyomyositis: characteristics at CT and MR imaging

Radiology

Gadolinium-DTPA-enhanced magnetic resonance imaging of musculoskeletal infectious processes

Skelet Radiol