[Hydronephrosis in the course of primary psoas abscess].

Primary psoas abscess is rare and presents a difficult diagnostic challenge. We present an unusual case of primary psoas abscess causing hydronephrosis in a 11-year-old boy. The presence of hydronephrosis complicated diagnosis, that was definitely confirmed by computerized tomography. Percutaneous drainage of the abscess under ultrasonography guidance combined with antibiotic therapy provided an effective treatment. Culture of the pus showed Staphylococcus aureus. The subject is discussed noting incidence, etiology and methods of treatment of primary and secondary psoas abscesses.