Fig. 3

A 61-year-old woman was admitted to the ICU with septic shock. Blood cultures were positive for Group A Streptococcus. Based on physical examination, the suspected focus of infection was the right elbow or right knee. Arthrotomy and washout were performed on both joints. A microbiologic culture of the synovial fluid of the right knee also showed Group A Streptococcus. Antibiotic treatment with ceftriaxone and clindamycin was started. Because the patient remained septic, only a minor amount of pus was drained from the right knee, and CRP and leukocyte count remained high at 450 mg/L and 13 × 10⁹/L, respectively, FDG-PET/CT was performed to identify another potential infection focus or to see if there was spread of infection. Fused coronal FDG-PET/CT (a), and coronal maximum intensity projection FDG-PET (b) showed increased FDG uptake in the right knee suggestive of arthritis (a, white arrow, b, orange arrow). By mistake, intravenous clindamycin infusion dissolved in 5% glucose and a continuous intravenous infusion with saline and 5% glucose solution were not stopped before FDG-PET/CT, resulting in increased FDG uptake of skeletal muscle (a dashed white rectangle, b dashed orange rectangle). Axial CT showed mild suprapatellar recess effusion (c, orange arrow). This was also visible on fused axial FDG-PET/CT (d, orange arrow), in addition to high intercondylar FDG uptake. No other evident infection focus was found on FDG-PET/CT, but the result was not conclusive due to high background uptake caused by inadequate patient preparation. Nevertheless, the patient slowly recovered and was discharged to a rehabilitation center three weeks after FDG-PET/CT