Empyema Necessitatis: Yet Another. Mimic of Necrotizing Fasciitis in the Torso. The radiologic manifestations of necrotiz- ing fasciitis, a fulminant and life- ...
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Letters Empyema Necessitatis: Yet Another Mimic of Necrotizing Fasciitis in the Torso The radiologic manifestations of necrotizing fasciitis, a fulminant and life-threatening infection of the soft tissues, and its potential mimics were illustrated and discussed in detail in the January 2015 issue of the AJR in an article by Chaudhry et al. [1]. Indeed, the authors have simplified the conundrum of multifarious (inflammatory, infections, and others) processes that can involve the soft tissues and confront the radiologist in daily practice. Because of the potential for fatalities and other dismal outcomes, radiologists should certainly be aware of the imaging spectrum of necrotizing fasciitis and its mimics, especially in an era in which immunocompromised hosts are escalating worldwide. These include diabetic patients, cancer and postchemotherapy patients, renal failure patients, HIV-AIDS patients, and posttransplantation and postsurgical patients, among others. Although Chaudhary et al. [1] discussed alcoholism as a cause of type-I necrotizing fasciitis, we underscore the significance of recognizing liver cirrhosis (irrespective of etiology) as an independent risk factor for necrotizing fasciitis. Liver cirrhosis as a cause is being increasingly recognized worldwide [2, 3]. Because of our experience working in a dedicated liver center and having encountered an increasing number of cases of necrotizing fasciitis in cirrhotic patients, we believe this cause warrants a pressing acknowledgment, particularly because
the prevalence of liver cirrhosis is on a sharp increase globally (largely attributable to increasing alcohol abuse, hepatitis-C infection, and nonalcoholic fatty liver disease). In addition, we propose empyema necessitatis as yet another mimic of necrotizing fasciitis that can involve the chest wall and perhaps should be added to the comprehensive list of differential diagnoses appraised by the authors in their well-illustrated article. Empyema necessitatis, or empyema necessitans, refers to the presence of fluid collections with or without air in the soft tissues of the torso occurring secondary to dissection of pus through the pleural space (empyema) [4] (Fig. 1). The entity was first described by Gullan De Baillon in 1640 [4]. Patients typically present with a subacute painful erythematous mass on the thoracic wall. The most common location of involvement is the anterior chest wall because the lung is more adherent to the pleura posteriorly. However, extensions into the abdominal wall, flank, breast, mediastinum, pericardium, and retroperitoneum have also been reported. Accordingly, potential complications include respiratory failure, cardiac failure, mediastinitis, hematogenous dissemination, septic shock, and renal failure. Mycobacterium tuberculosis remains one of the most common causative pathogens; others are Actinomyces israelii, Streptococcus pneumoniae, Staphylococcus aureus, and Pseudomonas cepacia [4]. Differentiation from necrotizing fasciitis or abscess-formation can be readily achieved using cross-sectional imaging, and CT is consid-
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ered the imaging modality of choice. Empyema necessitatis can be fatal if not promptly recognized and treated (antimicrobial therapy, drainage, or surgery) [4]. The morbidity and mortality are dependent on the causative organism, severity and duration of the infection, immune status of the host, and delay in diagnosis. In summary, radiologists should be mindful that an extension of purulent pleural liquid with or without air into the soft tissues of the torso can simulate necrotizing fasciitis. Timely identification can facilitate selection of appropriate therapy, which can be life-saving. Ankur Arora S. Rajesh Yashwant Patidar Institute of Liver and Biliary Sciences, New Delhi, India DOI:10.2214/AJR.15.14321 WEB—This is a web exclusive article.
References 1. Chaudhry AA, Baker KS, Gould ES, Gupta R. Necrotizing fasciitis and its mimics: what radiologists need to know. AJR 2015; 204:128–139 2. Hung TH, Tsai CC, Tsai CC, Tseng CW, Hsieh YH. Liver cirrhosis as a real risk factor for necrotising fasciitis: a three-year population-based follow-up study. Singapore Med J 2014; 55:378–382 3. Wang JM, Lim HK. Necrotizing fasciitis: eightyear experience and literature review. Braz J Infect Dis 2014; 18:137–143 4. Mizell KN, Patterson KV, Carter JE. Empyema necessitatis due to methicillin-resistant Staphylococcus aureus: case report and review of the literature. J Clin Microbiol 2008; 46:3534–3536
Fig. 1—53-year-old man with nonalcoholic steatohepatitis–related liver cirrhosis who presented with fever, cough, and tender left anterior chest wall swelling. A, Ultrasound image of chest wall shows deepseated left anterior chest wall fluid collection. B, Sagittal contrast-enhanced CT image shows transpleural spread of parapneumonic empyema (white arrow) into left anterior chest wall (black arrow) containing tiny air specks (arrowhead) in keeping with empyema necessitatis. Note focal consolidation of left upper lobe (asterisk). (Fig. 1 continues on next page)
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Letters Fig. 1—53-year-old man with nonalcoholic steatohepatitis–related liver cirrhosis who presented with fever, cough, and tender left anterior chest wall swelling. C, Coronal contrast-enhanced CT image shows left lung consolidation (asterisk) with transpleural spread of parapneumonic empyema (white arrow) into chest wall soft tissues (black arrow) containing tiny air specks (arrowhead). Ultrasound-guided tap and subsequent evaluation of pus revealed gramnegative bacilli (Escherichia coli). D, Follow-up CT image obtained after percutaneous aspiration and 2 weeks of antimicrobial therapy shows significant regression of chest wall (black arrow) and pleural fluid collections (white arrow).
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