Psoas disease causing a characteristic change in the ultrasonographic appearance of the psoas compartment

Twenty patients with ultrasonographic evidence of disease involving the psoas compartment were analysed retrospectively. The abnormality found was a mass lesion in the psoas muscle with increased or decreased echogenicity and a characteristic loss of the normal appearance of striated homogeneous bundles. Those examined included eight patients with abscesses, six with hematomas and six with tumor infiltration. All the abscesses were echopoor and showed absence of the normal appearance of the muscle. Such findings are non-specific because of the similar appearance of non-organized hematomas or lymphomatous infiltration. Organized hematomas and primary retroperitoneal tumors were echogenic but with loss of the normal appearance. Ultrasound guided needle aspiration is sometimes necessary to complete the diagnosis and may be a definitive strategy. We recommend ultrasonography for use in detecting psoas disease when appropriate clinical signs are present.