Most adults with uncomplicated acute pyelonephritis pose no diagnostic or therapeutic problems and recover fully. When imaging is requested in these cases, CT scan with and without contrast enhancement is preferable; however, depending on the condition of the patient and preference of the clinician an IVU, sonogram, or radionuclide scan may also provide adequate information. Patients at higher risk for complications, such as renal or perinephric abscesses with or without PHN and EPN, require aggressive and vigorous clinical and radiologic monitoring. CT scan is superior to other imaging modalities in the investigation of these complications. Interventional percutaneous procedures are established as safe and effective means of controlling or curing the infection in many patients and are often chosen over traditional surgical technique. The radiologist thus is an indispensable member of the management team and should be available for consultation and intervention.