Psoas sign (abdominal x-ray)
The psoas sign is a classic non-specific finding on the abdominal radiograph, potentially representing retroperitoneal pathology.
Normally on an abdominal radiograph, the lateral margins of both the psoas muscles are clearly visible due to adjacent fat. When the lateral edge of one, or both, psoas muscle(s) is no longer clearly demarcated, this is a positive psoas sign. Only a portion of the muscle edge needs to be obscured for the sign to be positive.
- 1. Williams SM, Hultman SA, Harned RK, Quaife MA. The psoas muscle: a reevaluation. doi:10.1148/radiographics.5.4.525