Sonographic measurement of transient synovitis in children: diagnostic value of joint effusion.

In an evaluation of the diagnostic criteria for ultrasonography (US) of transient synovitis in children, in a prospective study, 34 consecutive children with a painful hip underwent US. The ultrasonographic joint space (UJS) and the effusion space were measured in both hips, and the width of the UJS thickness in the asymptomatic hips was compared with that in the symptomatic hips. US showed the presence of a joint effusion in 31 of the 34 children and a bilateral effusion in 3. The US diagnostic criterion for hip effusion consists of a UJS thickness difference >2.0 mm between asymptomatic and symptomatic hips. However, we found that 8 of the 31 UJS measurements compared between symptomatic hips and asymptomatic hips exhibited differences of <2 mm. We suggest that effusion space measurements are possible for accurate visualization of synovitis, rather than the recording of differences in UJS measurements between hips.