[Retroperitoneal abscess. Report of 2 cases].

Two cases of retroperitoneal abscess that had recently been treated in our service are described. The primary infection was localized to the psoas muscle in one patient with a previous injury to the right lumbar region. The other case was secondary to an ascending urinary infection. Staph aureus were isolated in the first case and E. Coli in the second. The different clinical course and treatment of each case are described.