Man With Cat Bite

Abstract

A previously healthy 21-year-old man presented to the emergency department with worsening left thigh pain during 2 months. Physical examination result was significant for tenderness in the region of small puncture wounds to the left upper thigh (Figure 1). He reported he was bitten by a cat 2 months before. Knee and thigh examination results were otherwise unremarkable. Point-of-care ultrasonography demonstrated a septate hypoechoic mass (Figure 2). Contrast-enhanced computed tomographic (CT) scan revealed a multiloculated, intramuscular abscess with extension into the knee capsule, suggestive of septic arthritis (Figure 3).Figure 2Hypoechoic, septate mass in the longitudinal view on bedside ultrasonography (arrow).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Contrast-enhanced CT demonstrating a multiloculated, soft tissue abscess extending into the knee joint space, suggestive for septic arthritis (arrows).View Large Image Figure ViewerDownload Hi-res image Download (PPT) Pyomyositis with pyogenic arthritis. Pyomyositis is a collection of purulent material in the skeletal muscle, commonly occurring in the setting of systemic immunodeficiency, intravenous drug abuse, concurrent infection, or trauma. Although the majority of cases are due to Staphylococcus aureus, our patient’s traumatic inoculation was determined to be from oral cat flora. Patients typically present with pain localized to the involved muscle, with progression to significant tenderness, marked edema, and fever.1Crum N.F. Bacterial pyomyositis in the United States.Am J Med. 2004; 117: 420-428Abstract Full Text Full Text PDF PubMed Scopus (205) Google Scholar If pyomyositis is left untreated, systemic toxicity can result. In addition, pyogenic arthritis classically presents with an edematous, erythematous, and markedly tender joint with decreased range of motion. The patient presented with normal vital signs, appeared nontoxic, and demonstrated full range of motion of the affected thigh and knee. The sensitivity of point-of-care ultrasonography for soft tissue infection is approximately 96%, with a specificity of 83%.2Barbic D. Chenkin J. Cho D.D. et al.In patients presenting to the emergency department with skin and soft tissue infections what is the diagnostic accuracy of point-of-care ultrasonography for the diagnosis of abscess compared to the current standard of care? a systematic review and meta-analysis.BMJ Open. 2017; 7e013688PubMed Google Scholar,3Gottlieb M. Avila J. Chottiner M. et al.Point-of-care ultrasonography for the diagnosis of skin and soft tissue abscesses: a systematic review and meta-analysis.Ann Emerg Med. 2020; 76: 67-77Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar Evaluating for underlying soft tissue abscesses can be difficult and using bedside ultrasonography can aid in guiding further evaluation. Our patient underwent surgical drainage with arthrocentesis and was successfully discharged after a prolonged course of intravenous antibiotics.