[Giant psoas abscess with aggressive extension: report of a case].

We report a case of giant psoas abscess with aggressive extension outside the muscles of the iliopsoas component. A 57-year-old man was admitted to our hospital, presenting with right flank pain and severe general malaise. He had been diabetic, but no treatment had been performed for diabetes. Leukocytosis, positive CRP and hyperglycemia were noted, but he was nearly afebrile on admission. Computerized tomography revealed a large multilocular mass in the right retroperitoneal space involving the ipsilateral psoas muscle. The diagnosis was not apparent until the 12th hospital day, when moderate grade fever was noted and brownish purulent fluid was obtained by percutaneous puncture of the mass. Staphylococcus aureus was isolated on culture. Antibiotic chemotherapy was started, and ultrasound-guided percutaneous drainage was then performed under the diagnosis of psoas abscess. At that time, the abscess was aggressively extending from the iliopsoas component into the pelvic floor, involving the rectus muscle, the gluteal muscles and formation of subucutaneous lesions. At 46 days after drainage, surgical resection of the abscess with removal of the adjucent tissue was performed because of persistent discharge of pus and multiple residual lesions. The postoperative course was uneventful, and there has been no recurrence. Many cases of psoas abscess have been reported in the Japanese literature. Prompt drainage, either percutaneously or surgically are required. Surgical resection of the abscess, with not only opening the cavity but also removal of the adjacent tissue, may be recommended in some cases, especially those diffuse or multilocular lesions.