Acute pyelonephritis. Preventing complications through prompt diagnosis and proper therapy.

The diagnosis of pyelonephritis is based on clinical and laboratory criteria that include fever, flank pain or tenderness, leukocytosis, pyuria, and confirmatory urine culture. A Gram stain of unspun urine can provide an important early clue regarding the etiologic agent. At least 85% of cases are caused by Escherichia coli, but clinicians need to be aware of other potentially aggressive organisms as well. Elderly, diabetic, or immunocompromised hospitalized patients and patients subject to instrumentation present a more complex diagnostic challenge and require more intense parenteral treatment. Prompt diagnosis and proper therapy decrease the risk of serious complications.