A psoas abscess is an infection that produces a collection of pus within or adjacent to the psoas major muscle, a large muscle in the retroperitoneum that connects the spine to the hip. Psoas abscesses can arise primarily (from bloodborne bacteria) or secondarily (spreading from nearby infections of the spine, kidney, bowel, or hip joint). On ultrasound, a psoas abscess typically appears as a hypoechoic or mixed-echogenicity fluid collection within or adjacent to the enlarged psoas muscle. Internal debris, septations, and gas (appearing as bright echogenic foci) may be present. While CT provides a more comprehensive evaluation, ultrasound can detect the collection and guide percutaneous drainage, inserting a catheter through the skin under real-time imaging to drain the infected material.
Sonography Term