Doripenem is an antibiotic medication not yet approved by the US FDA. This is a phase 3, multi-center, prospective, open-label, single-arm study of doripenem in the treatment of complicated lower urinary tract infection or pyelonephritis in adults. Patients are hospitalized, but subsequently, patients may treated as outpatient or through home-based therapy at the discretion of the investigators. Conventional laboratory data will be collected from patients at specified times throughout the study. The primary endpoint is microbiological response measured at test of cure visit. The patients will receive doripenem with duration of therapy up to 10 days.