Which findings on ultrasonography are characteristic of septic arthritis (SA)?

Updated: Sep 19, 2019
  • Author: Lourdes Nunez-Atahualpa, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Answer

Answer

Effusions in septic arthritis tend to be hypoechoic, rather than echo-free, [30, 31]  and it has been suggested that an ultrasound that fails to show a fluid collection may virtually exclude the diagnosis. [30]

In the hip joint, the presence of joint asymmetry, the presence of fluid, and increased thickness of the articular capsule have been described as diagnostic criteria. [30]

Synovial hypertrophy has been observed in patients with tuberculosis, brucellosis, lyme disease, and fungal infections. [31]

US has been referred as the “orthopedic stethoscope“ [34]  and is considered the modality of choice in children because of the ease of image acquisition, [32]  obviation of sedation, and radiation-free safety profile. In pediatric patients, it can also suggest the need for further studies, such as an MRI, or the need for arthrotomy, irrigation, and/or debridement in patients with an irritable hip. [35]

It has also been suggested that ultrasound can help obviate the need for diagnostic joint aspiration in suspected septic arthritis while detecting the extent of the pathology. [33]

Besides B-mode ultrasonography, studies have been performed with other modes, such as a power Doppler, for which it has been suggested that an increased vascularity of the affected joint could exclude the diagnosis with certainty, but that has not been successful. [36]

US could potentially be used to estimate the size of joint effusions and abscesses and allow monitoring of treatment, although it has been described by MRI . [37]


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