SURGICAL INFECTIONS Volume 15, Number 4, 2014 ª Mary Ann Liebert, Inc. DOI: 10.1089/sur.2013.183

Rectus Femoris Pyomyositis Caused by Klebsiella pneumoniae Wan-Hsiu Liao,1 Chih-Cheng Lai,2 Shih-Horng Huang,3 and Sheng-Hsiang Lin 4,5


62-year-old male who had diabetes mellitus and posttraumatic left lower extremity atrophy presented to the emergency department with progressive right thigh pain for five days. Physically, a tender and swollen right thigh with crepitus during palpation was noticed; meanwhile, the overlying skin was intact without any eruptions. The white blood cell count increased (17,370 cells/ · 109L) with neutrophilia (74%) and impaired kidney function (blood urea nitrogen 62 mg/dL, serum creatinine concentration 3.5 mg/dL). Besides, hyperglycemia (blood sugar 543 mg/dL) and lactic acidosis (serum lactate concentration 13.7 mmole/L) were noted. Plain radiography of the right hip showed the presence of soft tissue gas in the right thigh (Fig. 1). Non-contrast computed tomography (CT) showed a swollen right rectus femoris muscle with abscess formation (Fig. 2). Pus was found on needle aspiration and the diagnosis of rectus femoris pyomyositis was confirmed. Thereafter, septic shock developed and he received endotracheal intubation. Antimicrobial therapy with piperacillin-tazobactam was initiated and the patient underwent surgical drainage and debridement promptly. Klebsiella pneumoniae was isolated from both blood and pus cultures; thus, ceftriaxone was used instead and continued for four weeks. The post-operative course was uneventful and he was discharged five weeks later without major sequelae. Pyomyositis, a rare clinical entity, is a bacterial infection of skeletal muscle and the primary form is believed to be a complication of transient bacteremia [1]. Staphylococcus aureus is the most common causative pathogen, followed by streptococci; by contrast, gram-negative bacilli are relatively uncommon [1,2]. The most frequent site of infection is the quadriceps muscle, followed by the gluteal and iliopsoas muscles [1]. The reported mortality of primary pyomyositis ranges from 1 to 8%, depending on the baseline comorbidities; furthermore, patients in a later stage who present with sepsis, hemodynamic compromise or organ dysfunction have a higher mortality rate [2,3]. The standard treatment of pyomyositis includes antibiotic therapy and immediate drainage of the purulent material, especially in patients presenting with sepsis [1]. For this reason, early diagnosis is of

considerable importance and a high index of suspicion is required because there may be a lack of change on overlying skin [2]. Screening plain radiograph might show soft tissue gas but its utility is limited by the low sensitivity [1]. On the other hand, CT and magnetic resonance imaging (MRI) would provide a better illustration, and the diagnostic performance of CT is non-inferior to MRI [4]. The CT findings of pyomyositis are characterized by fascial air, muscle enlargement with heterogeneous attenuation, focal fluid collection, and ring enhancement after injection of contrast

FIG. 1. Plain radiography of the right hip revealing soft tissue gas in the right thigh (arrow).

1 Department of Family Medicine, 3Department of Surgery, 4Department of Internal Medicine, New Taipei City Hospital, New Taipei, Taiwan 2 Department of Intensive Care Medicine, Chi-Mei Medical Center, Liouying, Tainan, Taiwan 5 Department of Respiratory Therapy, Fu-Jen Catholic University, New Taipei, Taiwan




the majority of cases are caused by gram-positive bacteria, broad-spectrum antibiotics are necessary pending final culture reports. References

1. Bickels J, Ben-Sira L, Kessler A, et al. Primary pyomyositis. J Bone Joint Surg Am 2002;84-A:2277–2286. 2. Crum NF. Bacterial pyomyositis in the United States. Am J Med 2004;117:420–428. 3. Sharma A, Kumar S, Wanchu A, et al. Clinical characteristics and predictors of mortality in 67 patients with primary pyomyositis: A study from North India. Clin Rheumatol 2010;29:45–51. 4. Gordon BA, Martinez S, Collins AJ. Pyomyositis: Characteristics at CT and MR imaging. Radiology 1995;197:279– 286. 5. McGillicuddy EA, Lischuk AW, Schuster KM, et al. Development of a computed tomography-based scoring system for necrotizing soft-tissue infections. J Trauma 2011;70: 894–899.

FIG. 2. Non-contrast computed tomography of bilateral thighs showing a swollen right rectus femoris muscle with areas of low attenuation and gas formation (arrows), and atrophy of left thigh muscles. medium [4,5]. In our case, contrast medium was avoided because of impaired kidney function and the changes in CT attenuation were relatively faint but identifiable. To summarize, early recognition by CT imaging and aggressive surgical debridement are crucial for pyomyositis. Although

Address correspondence to: Dr. Sheng-Hsiang Lin Department of Internal Medicine New Taipei City Hospital No. 3, Section 1, New Taipei Blvd., San-Chong District New Taipei City 24141 Taiwan E-mail: [email protected]

Rectus femoris pyomyositis caused by Klebsiella pneumoniae.

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