summary Psoas Abscess is an infection of the psoas muscle that may present in the pediatric population and must be considered when evaluating hip pain in children. Diagnosis generally requires MRI studies to evaluate for a psoas abscess. Treatment is percutaneous image-guided drainage and antibiotics in most cases. Epidemiology Demographics more common in tropics Etiology Pathophysiology may spread to hip joint causing septic arthritis because of indirect passage via psoas bursa lies between hip joint and psoas connects psoas directly to hip joint in 15% of cadavers direct passage between the iliofemoral and iliopubic ligaments Microbiology Staph aureus most common organism Associated conditions septic hip - pediatric tuberculous spondylitis Presentation Symptoms presents like hip septic arthritis fever hip pain limp or refusal to bear weight Physical exam inspection hip rests in a position of flexion palpation may have tender mass in iliac fossa provovative tests psoas sign pain caused by extension and internal rotation of the limb Imaging Radiographs recommended views AP and frog-leg lateral pelvic x-rays to rule out septic hip findings may show loss of definition or enlargment of psoas muscle shadow Ultrasound diagnostic imaging study of choice Bone scan helpful in diagnosis CT scan with contrast indications can confirm diagnosis when ultrasound or MRI not available avoid if possible due to radiation exposure findings include the presence of a mass and local attenuation within the involved musclee, with ring enhancement may be negative in early stages MRI indications can confirm diagnosis if ultrasound not available difficult to obtain expeditiously findings will show changes early in the disease process Treatment Nonoperative percutaneous ultrasound or CT-guided drainage indications treatment of choice in most cases Operative open drainage indications useful for secondary psoas abscess e.g. spread from the bowel can simultaneously address intraabdominal source Complications Septic arthritis psoas abscess can spread to hip joint Sepsis