Ultrasound imaging has many clinical applications, but there is a lack of data about its use by infectiologists. The aim of this study was to describe ultrasound performed routinely by infectiologists and to assess the diagnostic performance of ultrasound with aspirate and fluid analysis in prosthetic joint infections.

Retrospective study between 1^st June 2019 and 1^st June 2020 in an infectious and tropical diseases unit in a tertiary University Hospital.

One hundred and thirty-one ultrasounds were performed on 127 patients by the infectious diseases team. These included 64 musculoskeletal ultrasounds (31 in native joints and 33 in prosthetic joints including 15 knees, 13 hips and 5 spacers) and 33 led to a fluid aspirate. Fourteen lung ultrasounds were done, 11 confirmed pneumopathy and 7 resulted in pleural puncture. Twenty-three vascular ultrasounds were done, 17 to insert a catheter, and four to perform a blood test. Five ultrasounds explored adenopathy, of which one node tuberculosis and one Bartonella infection were diagnosed. In prosthetic joint infections, sensitivity and specificity of ultrasound with fluid aspirate and analysis were respectively 100% and 100% for the knee and 40% and 100% for the hip.

Ultrasound performed by infectiologists is useful and contributes to a faster diagnosis. Furthermore, the specificity of ultrasound with aspirate and fluid analysis is very high in prosthetic joint infection. Ultrasound training courses should be considered for infectiologists including residents.