The role of ultrasound in differentiating septic arthritis from transient synovitis of the hip in children.

A total of 154 children admitted with septic arthritis (n=81) or transient synovitis (n=73) were studied retrospectively. Ultrasound findings for 127 patients were correlated with the final diagnosis. Sensitivity, specificity and positive predictive value of ultrasound for the diagnosis of pediatric septic hip were 86.4, 89.7 and 87.9%, respectively. Unsatisfactory outcome occurred more significantly in children, for whom treatment was initiated more than 4 days after the onset of symptoms and those who had a false-negative ultrasound study. Ultrasound cannot be used safely to distinguish between pediatric septic hip and transient synovitis. It may be a method of value to detect minimal hip effusion. A predictive algorithm using clinical, laboratory and ultrasound findings could be beneficial.